PROSTHESES : an artificial substitute for a missing body part, such as an arm or leg, eye or tooth, used for functional or cosmetic reasons, or both.

Table of contents :

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bone prostheses bionic restoration of movement blood substitutes saliva substitutes artificial tears vitreous substitutes tear substitutes heart prostheses ventricular reshaping mechanical circulatory support cardiac valves closure of patent foramen ovale vascular grafts stenting intravascular stents for aneurysms vena cava filters artificial larynx penile implants hearing aids cochlear implants bionic restoration of movement artificial tendons biofuel cells artificial muscles

see also : extracorporeal membrane oxygenation (ECMO) renal replacement therapy (RRT) bioartificial kidney bioartificial liver

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Materials :

metallic prostheses : cobalt and chromium alloys, stainless steel, titanium, polyvinyl, polyuretane or polyesters (for soft tissues), tantalum or acrylic resins (for bony structures)

organic prostheses : polyethylene, teflon, dacron, nylon, polytef / polytetrafluoroethylene (PTFE) (a polymer of tetrafluoroethylene, used as a surgical implant material for prostheses, such as artificial vessels and orbital floor implants and for many applications in skeletal augmentation and skeletal fixation. Also used widely in industry, e.g., as an antistick coating for cooking utensils), silicone (for breast, testicular, and outer ear)

biological prostheses :

• autologous :
• saphena vein for tibial and coronary revascularization
• left internal mammary artery (LIMA) for coronary revascularization
• splenic artery and hypogastric artery for visceral revascularization
• homologous : human umbilical vein (Dardik prosthesis) covered by a dacron mesh
• heterologous : bovine carotid and mammary arteries, ovine collagen prostheses

Thrombotic threshold velocity (TTV) : the minimum velocity of blood flow through a vascular graft or prosthesis below which thrombogenicity would begin along the intimal surface; variables affecting it include lumen diameter and type of material the graft or prosthesis is made of

• alloplastic prostheses : 150-200 ml/min
• biological prostheses : 50-150 ml/min
• autologous saphena vein (without valves or with valves in opposite orientation) (in femoral and below knee distal bypass) : 30-50 ml/min

• implantology : the science dealing with the study and practice of inserting implants (an object or material, such as an alloplastic or radioactive material or tissue, partially or totally inserted or grafted into the body for prosthetic, therapeutic, diagnostic, or experimental purposes)
• engineering : the application of physical, mathematical, and mechanical principles to practical purposes.
• biomedical engineering / bioengineering : the use of engineering in biomedical technology such as the analysis of movement of body parts or prosthetics
• tissue engineering : application of the methods and principles of engineering to gain an understanding of the relationship between structure and function in both normal and pathological tissue and to develop possible substitutes for pathological tissue

Immune response is suppressed by polymers with the following characteristics :

• hydrophilic surfaces
• containing negatively charged chemical groups

These properties induce apoptosis in 50% of sticking macrophages and survivor ones are unable to create scar tissue, improving lasting of the prosthesis.

• bone prostheses
• microinterlock : the growth of mineralized bone into the porous surface of a specially constructed prosthesis, anchoring the prosthesis into place.
• vertebroplastic for vertebral fractures : polymethylmethacrylate (PMMA) solidifies and the exothermic reaction burns periosteal sensitive fibers.
• cranioplasty (skull prostheses) : plastic operation on the skull; surgical correction of defects of the skull. Porous hydroxyapatite which can be colonized by osteoblasts within 5-6 months.
• durapatite : a crystalline form of the compound (Ca₃(PO₄)2)3·Ca(OH)2 (see hydroxyapatite), used as a prosthetic aid
• duraplasty : a plastic operation on the dura mater; graft of the dura.
• arthroplasty / joint replacement : plastic surgery of a joint or of joints; the formation of movable joints
• arthroprosthesis / total joint arthroplasty / total joint replacement : arthroplasty in which both sides of a joint are removed and replaced by artificial implants anchored to the bones
• TMJ prostheses :
• interposition arthroplasty : surgical correction of ankylosis of the temporomandibular joint by separating the immobile fragment from the mobilized fragment and interposing a substance, such as fascia, cartilage, metal, or plastic, between them.
• intracapsular temporomandibular joint arthroplasty : operative recontouring of the articular surface of the mandibular condyle without the removal of the articular disk.
• hip prostheses :
• Austin Moore arthroplasty : hip reconstruction surgery using an Austin Moore prosthesis (metallic implant)
• Charnley's hip arthroplasty : a hip replacement operation involving insertion of Charnley's prosthesis (acetabular cup and a relatively small femoral head component that form a low-friction joint)
• Thompson arthroplasty : hip reconstruction surgery using a Thompson prosthesis (a Vitallium implant)
• knee prostheses :
• total knee arthroplasty : arthroplasty of both sides of the knee joint.
• foot prostheses :
• Flex-Foot : trademark for a type of ankle-foot prosthesis that includes a flexible rod replacing the lower leg and foot as well as a heel replacement component allowing push-off.
• solid ankle cushion heel (SACH) foot : a type of prosthetic foot that allows flexion, extension, inversion, and eversion
• Seattle foot : a type of prosthetic foot that allows flexion, extension, inversion, and eversion, and allows some push-off when walking; it is made of plastic and resembles a normal human foot.
Treatment of large defects requires the harvest of fresh living bone from the iliac crest. Harvest of this limited supply of bone is accompanied by extreme pain and morbidity. This has prompted the exploration of other alternatives to generate new bone using traditional principles of tissue engineering, wherein harvested cells are combined with porous scaffolds and stimulated with exogenous mitogens and morphogens in vitro and/or in vivo. Large volumes of bone can be engineered in a predictable manner, without the need for cell transplantation and growth factor administration. The crux of the approach lies in the deliberate creation and manipulation of an artificial space (bioreactor) between the tibia and the periosteum, a mesenchymal layer rich in pluripotent cells, in such a way that the body's healing mechanism is leveraged in the engineering of neotissue. Using the "in vivo bioreactor" in New Zealand White rabbits, bone that is biomechanically identical to native bone has been engineered. The neo-bone formation followed predominantly an intramembraneous path, with woven bone matrix subsequently maturing into fully mineralized compact bone exhibiting all of the histological markers and mechanical properties of native bone. The bone was harvested after 6 weeks and transplanted it into contralateral tibial defects, resulting in complete integration after 6 weeks with no apparent morbidity at the donor site. Furthermore, in a proof-of-principle study, by inhibiting angiogenesis and promoting a more hypoxic environment within the "in vivo bioreactor space," cartilage formation can be exclusively promoted^ref.
• distraction osteogenesis : a process whereby attachment of the device across a surgical bone cut separates the bone ends in a precise, continuous manner that results in the formation of healthy bone tissue at a rate of 1 mm per day. The bone generator device (GenerOs SB, made by Orthonetx, Inc.) corrects bone deficiencies and deformities in small bones of the hands, wrists, feet, and ankles, and pediatric forearms. Previously approved GenerOs devices include a craniofacial bone generator (GenerOs CF), a limb strengthener (GenerOs EX), and a dental implant distractor (GenerOs DI).
• cineplastic surgery : creation of a skin-lined tunnel through a muscle adjacent to the stump of an amputated limb, to permit use of the muscle in operating a prosthesis.
• antireflux prosthesis : a ring-shaped device that is placed around the esophagus above the stomach and below the diaphragm for treatment of gastroesophageal reflux and hiatal hernia
• Angelchik prosthesis : a C-shaped silicone device that wraps around the distal esophagus for treatment of reflux esophagitis or during laparotomy.
• oral prostheses
• cleft palate prosthesis : a prosthetic device, such as an obturator, used to correct cleft palate
• dental prosthesis : a replacement for one or more of the teeth or other oral structure, ranging from a single tooth to a complete denture
• implantodontics / dental or oral implantology / implantodontology : the branch of dentistry dealing with the implantation of artificial devices and materials into the oral hard and soft tissues for prosthetic, therapeutic, or diagnostic purposes
• dental implant : a prosthetic device of alloplastic material implanted into the oral tissues beneath the mucosal or periosteal layer or within the bone to provide support and retention to a partial or complete denture.
• endosseous or endosteal implant : a dental implant made of metal or sometimes ceramic or polymeric material, consisting of a blade, screw, pin, or vent, inserted into the jaw bone through the alveolar or basal bone, either directly or through the root canal and apex of a tooth, with a post protruding through the mucoperiosteum into the oral cavity to serve as an abutment for dentures or orthodontic appliances, or to serve in fracture fixation.
• osseointegrated implant : an endosseous implant containing pores into which osteoblasts and supporting connective tissue can migrate. Metallic, ceramic, and polymeric materials have been used.
• Brânemark implant : a type of osseointegrated implant consisting of a two-stage system of titanium screws.
• intraperiosteal implant : a frame that conforms to the shape of the jawbone and is implanted beneath the outer or fibrous layer of the periosteum so that it rests firmly on the bone, with a post protruding into the oral cavity to serve as an abutment for dentures; used most commonly for upper fixed partial dentures and in the treatment of cleft palate.
• subperiosteal implant : a dental implant consisting of a metal frame implanted under the periosteum and firmly bound by the mucoperiosteum, resting on the jaw bone, with a post protruding into the oral cavity; used most commonly as an abutment for upper fixed partial dentures and in the treatment of cleft palate.
• transmandibular implant : a dental implant consisting of baseplate, cortical screws, threaded posts, and a superstructure that attaches to a denture, inserted via submandibular incision and fixed to the symphyseal border. The implant transverses the mandible, bears the denture directly, and is designed for patients with severe mandibular alveolar atrophy.
• Bosker implant : a common type of transmandibular implant
• transosteal implant : a dental implant consisting of a bolt that crosses the mandible and is secured in place by a nut; a post protrudes into the oral cavity and serves as an abutment for dentures or orthodontic appliances.
• endodontic implant : a metallic implant extending through the root canal of a tooth into the periapical bone structure, thereby lengthening the root of a pulpless tooth.
• magnet implant / denture magnet : a magnet made of a nonreactogenic platinum-cobalt alloy or a rare earth element, used for additional retention of dentures. One magnet is implanted into the mandible under the periosteum and the other is attached to the denture, its poles being opposite of those in the mandible
• the conventional treatment of dental caries involves mechanical removal of the affected part and filling of the hole with a resin or metal alloy. But this method is not ideal for tiny early lesions because a disproportionate amount of healthy tooth must be removed to make the alloy or resin stick. A dental paste of synthetic enamel rapidly and seamlessly repairs early caries lesions by nanocrystalline growth, with minimal wastage of the natural enamel^ref.
• maxillofacial prosthesis : a prosthetic replacement for those regions in the maxilla, mandible, and face that are missing or defective because of surgical intervention, trauma, pathology, or development malformations
• a major goal of research in bone transplantation is the ability to avoid creation of secondary bone defects.
• heterotopic bone induction : custom-built, bioengineered jaw transplant was implanted in a 56-year-old man in June 2004, who had part of his jawbone removed after a tumour spread through the area. A 3-D CT scan was taken of the patient's jaw (upper) and used to generate a virtual jawbone (lower), then used to create a scale model made of Teflon. They then fitted a lightweight titanium mesh around the replica, and removed the Teflon to leave a perfectly sculpted, hollow, U-shaped tube. The cylinder was filled with a natural bone mineral called hydroxyapatite, 20 mL of blood from the patient's own bone marrow, and a dash of  7 mg bone morphogenetic protein 7 (BMP7). The bone mineral offered structural support as BMP7 coaxed stem cells inside the blood to form new bone. Next, the replacement jaw needed to develop its own blood supply, so the team grafted it into a region rich in blood vessels inside the man's right latissimus dorsi muscle. 7 weeks later, medics removed the mandible and slotted it into the skull. Microsurgery was used to connect the jaw's newly developed blood supply with that of the head. In-vivo skeletal scintigraphy showed bone remodelling and mineralisation inside the mandibular transplant both before and after transplantation. CT provided radiological evidence of new bone formation. Postoperatively, the patient had an improved degree of mastication and was satisfied with the aesthetic outcome of the procedure. By the 4th week post-transplantation the patient enjoyed his first dinner in 9 years (bread and sausages); before reconstruction he had only been able to eat soft food and soup^ref. The procedure is an advance on alternative methods, where surgeons remove bone from hip or leg bones and carve it into a rough jaw shape before grafting it into the face. The jaw is rarely a perfect fit and it injures the hip or leg : this can cause pain and joint problems. Before the operation, the patient had a cosmetic, titanium jawbone that was covered with skin. Although this looked reasonably normal, the patient was unable to chew and dined solely on soft food and soup. Around 10% of surgery centres worldwide are set up to perform operations like this
• speech-aid prosthesis / artificial palate or velum / obturator / prosthetic speech aid : a device designed to close a cleft of the hard or soft palate and to substitute for structures used for normal speech
• palatal lift prosthesis : a type of speech-aid prosthesis sometimes used to aid in closure in cases of velopharyngeal insufficiency.
• artificial larynx / electrolarynx : an electromechanical device that enables a totally laryngectomized person to speak. When it is placed against the region of the laryngectomy a buzzing sound is produced, which is converted into simulated speech by movements of the organs of articulation (lips, tongue, glottis)
• penile implants or prosthesis : a semirigid rod or inflatable device implanted in the penis to provide an erection in men with organic impotence. Much has been written about sildenafil, which has revolutionised the treatment of erectile dysfunction. However, in some countries, including the United Kingdom, the cost of sildenafil is not reimbursed by the state for most men with erectile dysfunction. General practitioners in the United Kingdom can now prescribe the drug privately, and several guidelines have been produced to inform and educate general practitioners about the investigation and treatment of erectile dysfunction. Insertion of penile prostheses is still required for men in whom sildenafil is ineffective and who do not respond to or dislike intracavernosal injections or vacuum devices, particularly men with diabetes, cardiovascular disease, or neurological disease. Surgical treatment may also be required in some patients with Peyronie's disease. In penile prostheses this can be devastating and, frequently, results in removal of the device despite aggressive antibiotic therapy^ref. The incidence of infection associated with primary implantation ranges from 1 to 3%^{ref1, ref2, ref3}. In reoperation for revision or reimplantation the infection rate is higher, with reported rates ranging from 10 % to 13 %^{ref1, ref2, ref3}. In recent years, new strategies have been developed in an attempt to minimize this risk, expecially the use of an antibiotic coating on the device^ref
• 3-piece inflatable implants (75%) : inflatable cylinders in the corpora cavernosa, small pump in the scrotum and reservoir filled with saline solution placed deep in the abdomen. Gently squeezing the concealed pump in your scrotum several times moves the saline solution from the reservoir into the cylinders. As the cylinders fill, the penis becomes erect and firm. To end the erection, simply press a "deflation site" on the pump. Deflating the cylinders transfers the fluid back to the reservoir and the penis becomes flaccid
• 2-piece inflatable implants (15%) : inflatable cylinders in the corpora cavernosa and a small pump in the scrotum. The device is completely concealed and unobtrusive. The pump inflates the cylinders by transferring fluid within the system. A simple deflation technique then transfers fluid to return the penis to a flaccid state
• semi-rigid malleable (positionable) rods (10%) : 2 bendable, "positionable" rods into the penis. The rods have an outer coating of silicone and inner stainless steel core or interlocking plastic joints. For intercourse, the man places his penis in the erect position. As he does so, the rods inside his penis bend. To conceal the penile implant, the man bends his penis down. He can bend the device in more than one place to create the desired erection.
The device is completely hidden and unobtrusive. It commonly takes about 4-6 weeks to regain sexual function. Complications can occur, including infection and device malfunction
• Hydroflex penile prostheses
• AMS hydraulic penile prostheses
• vacuum erection device has 3 main parts: a plastic cylinder that the man places his penis into, a hand or battery operated pump that draws air from the cylinder and creates a vacuum that allows increased blood flow to the penis, causing an erection, and 1 or more tension rings placed on the base of the penis after vacuum erection is created to help maintain the erection by reducing blood flow out of the penis. A vacuum erection device will generate an erection that lasts for up to 30 minutes aided by the tension ring. Some side effects are possible: reddish pinpoint-size dots on the surface of the penis when negative pressure is applied too rapidly, some bruising if the penis is held under pressure too long, uncomfortable cold glans as the device and tension rings limit circulation, impaired ejaculation, and pain ata application of the tension rings. The vacuum erection device can be cumbersome to use and interfere with romantic spontaneity : for that reason, a vacuum erection device probably is best suited to a man in a stable relationship with a supportive sexual partner.
• neural prosthetics
• auditory brainstem implant : the past 15 years has seen much progress in restoring hearing to deaf patients. Cochlear implants were successfully introduced for patients with inner ear deafness. However, in rare cases when both auditory nerves are destroyed, such as in neurofibromatosis type 2 or after traumatic lesions, a cochlear implant cannot be used. Auditory brainstem prostheses have been developed for these patients that work by electrical stimulation of the second auditory neurone in the brainstem. The implant has been developed from single channel electrodes positioned in the brainstem^ref, to the 21 channel model currently used in Europe. Like patients with cochlear implants, patients with auditory brainstem implants wear a body level speech processor and a transmission coil on the scalp. The electrodes are placed in the lateral recess of the fourth ventricle, adjacent to the cochlear nuclei. Hearing results are not as good as with cochlear implants^ref. Only a few patients with auditory brainstem implants can understand closed set speech without lip reading, but many patients report that the device improves their conversational ability significantly because it helps lip reading^{ref1, ref2}. Experience with multichannel auditory brainstem implants is limited because of the low incidence of patients with neurofibromatosis, but the implants are a promising way of improving hearing in these patients. Continuing research and refinement of hardware and software will help to improve the hearing of patients with neurofibromatosis further.
• hearing aids : amplify sound
• bone anchored hearing aids (BAHA)
• implantable hearing aid
• SOUNDTEC semi-implantable hearing aid
The recent development of digital hearing aids has been a big step forward in overcoming hearing impairment^{ref1, ref2}. The hearing aids work by converting an incoming analogue signal into a digital one, which is then processed by a microprocessor and then changed back into an analogue signal before output^ref. Schematic illustration of a digital hearing aid (modified according to Steffens^{ref1, ref2})

The main advantages of the digital technique are that the signal can be processed to suppress noise or to amplify specific frequencies or sounds^ref. The latest generation of digital hearing aids can recognise speech, which allows them to suppress other noise and make hearing clearer. The multiprogram devices can adapt to specific situations in the patients' everyday lives, especially with noise suppression, which further improves the ability to hear. The enhanced sound quality of the digital amplifying system also make voice and sound more similar to reality, increasing the acceptability to patients. Other advantages include greatly reduced feedback and easier handling. The development of "real" binaural interactive signal processing may provide even better hearing in noisy environments^ref.
Hearing loss of almost any extent can be ameliorated with a hearing aid. For conductive hearing loss this is simply a matter of amplification, although for sensorineural hearing loss the mechanism is more complex. However, there are many factors which will interfere with a patient's satisfaction with, and benefit from, a hearing aid. Lack of motivation because of fear of stigmatisation, low expectations of benefit, or failure to accept there is a problem remain significant obstacles. Stephens et al showed that despite the fact that 50% of those aged 50-65 in two villages in South Wales had a hearing disability only 7% had a hearing aid^ref. Clinicians have an important role in identifying those who would benefit from a hearing aid and emphasising the benefits of its use. Hearing aids should have electroacoustic characteristics which make speech audible but comfortable. All consist of a microphone, which converts acoustic signals to electrical signals, an amplifier which selectively processes the output signals, a receiver which converts the electrical signal back to an acoustic signal, and an earmold and tubing to deliver this to the patient's ear. All hearing aids available on the NHS are behind-the-ear types (although it is common practice to supply some other aids to war veterans whose hearing impairment is due to bomb blasts).In behind-the-ear aids the microphone, amplifier, and receiver are in a crescent shaped plastic case that rests behind the ear. A small tube connects this to the earmold. This style remains popular with older people as it can provide higher gain and the larger controls are easier to manipulate. For those with severe hearing impairment or manual dexterity problems larger devices are needed, but these can be worn quite unobtrusively attached to clothing. Also available on the market from registered dispensers are in-the-ear and in-the-canal styles
• behind-the-ear (BTE)



• in-the-ear (ITE)
• in-the-canal (ITC)
• body worn aids


On most hearing aids there are 3 switch positions: O, T, and M. At the O position the hearing aid is off, and M denotes the microphone is on. At the T position (telecoil on) the aid can pick up signals from transmitting devicesfor example, certain telephones and loop systems which are now incorporated into the majority of concert halls, theatres, and customer service points at post offices and banks. A sympathetic hearing scheme symbol (ear with a line through it) denotes a loop system is in operation. A frequently encountered problem is a constantly whistling hearing aid. The clinician must exclude a canal blocked with wax, and ensure the hearing aid has not become unseated before referral for audiological reassessment. Like dentures, hearing aids may become loose when patients loose weight and new earmolds may need fitting. Quality of life improvements with hearing aids occur after 6 weeks and can be shown to be sustained after 1 year^ref. Such benefits are comparable in younger and older adults^ref
• prosthetic stapes
• Robinson prosthesis : a type of stainless steel prosthetic stapes.
• cochlear implants
• Clarion cochlear implant
• Iowa/Nucleus 10 mm electrode
• endosteal electrode : residual hearing might better be preserved if the implanted electrode permits the fluid-filled inner ear space to remain intact^ref
A cochlear implant is a small, complex electronic device that can help to provide a sense of sound to a person who is profoundly deaf or severely hard of hearing. The implant is surgically placed under the skin behind the ear. An implant has 4 basic parts :
• microphone, which picks up sound from the environment;
• speech processor, which selects and arranges sounds picked up by the microphone;
• transmitter and receiver/stimulator, which receive signals from the speech processor and convert them into electric impulses;
• electrodes, which collect the impulses from the stimulator and send them to the brain.
An implant does not restore or create normal hearing. Instead, under the appropriate conditions, it can give a deaf person a useful auditory understanding of the environment and help him or her to understand speech. Cochlear implants compensate for damaged or non-working parts of the inner ear. When hearing is functioning normally, complicated parts of the inner ear convert sound waves in the air into electrical impulses. These impulses are then sent to the brain, where a hearing person recognizes them as sound. A cochlear implant works in a similar manner. It electronically finds useful sounds and then sends them to the brain. Hearing through an implant may sound different from normal hearing, but it allows many people to communicate fully with oral communication in person and over the phone. Different types of deaf and severely hard of hearing people choose cochlear implants. Both children and adults can be candidates for implants. According to the Food and Drug Administration 2002 data, approximately 59,000 people worldwide have received implants. In the USA, about 13,000 adults have cochlear implants and nearly 10,000 children have received them. Adults who have lost all or most of their hearing later in life can often benefit from cochlear implants. These older candidates can often associate the sounds made through an implant with sounds they remember. This may help them to understand speech without visual cues or systems such as lipreading or sign language. Young children can also be candidates for implants. Cochlear implants, coupled with intensive post-implantation therapy, can help young children to acquire speech, language, developmental, and social skills. The best age for implantation is still being debated, but most children who receive implants are between 2 and 6 years old. Earlier implantation seems to perform better. A cochlear implant is a surgical procedure. The decision to receive an implant should involve discussions with many medical specialists and an experienced surgeon. The process is expensive. Some may choose not to have a cochlear implant for a variety of personal reasons. Also, though surgical implantation is almost always safe, complications are a risk factor, just as with any kind of surgery. An additional consideration is learning to interpret the sounds created by an implant. This process takes time and practice. Speech-language pathologists and audiologists are the professionals frequently involved in this learning process. Not everyone performs at the same level with a cochlear implant. Prior to implantation, all of these factors need to be discussed. The technology behind cochlear implants is changing rapidly. With advancements in technology and continued follow-up research with people who have already received implants, researchers are evaluating new opportunities and additional possible candidates for cochlear implants.

Our ability to learn language is already on the wane by our third year of life, according to a study of profoundly deaf children given cochlear implants to restore some of their hearing. The research supports the widely held belief that there is a 'sensitive period' for language learning, during which the capacity to acquire vocabulary and grammar is heightened.  The implants, which are surgically inserted in the ear, convert sound into electrical signals that the brain can interpret, allowing many deaf people to hear. The rate of language learning measured with the widely used Reynell Developmental Language Scales, which test a child's vocabulary and understanding of grammar, was greatest for those given implants before they turned 2 (still relatively rare). Children given implants at 3 or 4 years of age acquired language skills more slowly, although these children still benefited from the devices. Some evidence for a sensitive period of language formation comes from the tragic cases of feral or isolated children, who were cut off from any language stimulus in their formative years and never learned to speak using proper syntax. But the physical and emotional deprivation that these children suffer almost certainly affects their ability to interact with people, having a knock-on effect on their language skills. It's hard to tease out those effects. The ultimate test would be what Svirsky calls the 'forbidden experiment': deliberately depriving children of all language input, which is obviously impossible. Instead, many researchers in this field observe the progress of profoundly deaf children given implants. It's not a perfect way of studying language development, but it's a new and exciting source of evidence. The Food and Drug Administration approves cochlear implantation in children as young as 12 months old, and even earlier in special cases, but < 33% of patients receive it before age 2. Cochlear implantation is deeply controversial. The procedure has sometimes been billed as a 'cure' for deafness, but a lot of deaf people don't feel the need to be 'cured'. Parents should not be rushed into making decisions about surgery on their child : early communication isn't just about speech, pointing out that the child's sensitive period is just as useful for developing sign language. Cochlear implants are not a miracle for most children : the best solution would be for children with implants to learn sign language and speech simultaneously, as a bilingual approach seems to boost general language skills.
Web resources :
• Cochlear implants at NIDCD
• American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS)
• Alexander Graham Bell Association for the Deaf and Hard of Hearing (AG Bell)
• Cochlear Implant Association, Inc. (CIAI) Executive
• House Ear Institute (HEI)
• League for the Hard of Hearing (LHH), New York
• Combined Health Information Database (CHID)
• bionic restoration of movement : many paralysed people control computers with their eyes or tongue. But muscle function limits these techniques, and they require a lot of training.

bionic approach (with electrodes implanted or external)	candidate users	actuator types
brain-machine interface (BMI)	completely paralyzed persons who can benefit from mechanical assist devices	motors, i.e., robotic arms controlled by monkeysref
brain-computer interface (BCI) invasive noninvasive	completely paralyzed persons who wish to simply communicate	computer screen, i.e., moving a cursorref Braingate (source : Cyberkinetics Inc) recognizes brain signals for movement still generated by immobile patients and converts them into action on a computer screen. A 16-mm2 chip containing 100 electrodes is implanted into the brain during a 3-hour procedure to record cell activity while an external PC sized processor converts the signals from the simultaneous firings of 100 individual neurons into computer instructions. FDA gave approval to implant chips in the motor cortex region of 5 quadriplegic patients to give them mouse control and computer access : in June 2004, surgeons implanted it into the motor cortex of a 24-year-old quadriplegic, allowing the patient to control a computer or television using his mind, even when doing other things at the same time. Macaque monkeys bearing implants to the parietal and primary motor cortices can learn, via visual feedback, to make a robotic arm reach, grasp, and gripref. In an algorithm called "continuous shared control", the robots contain tactile sensors that provide local intelligence – akin to a cat's whiskers : controlling the robot via a combination of local intelligence and monkey brainpower seems to make the tasks a lot more reliable than having solely brain-based control. BrainGate could be coupled wwith functional electrode stimulation (FES), in which partially paralyzed patients achieve some control of paralyzed limbs by stimulating electrodes placed in the muscles of those limbs. Current FES systems rely on external signals, but now imagine if we could hook up the sensor directly to this FES system : now by thought alone these people could be controlling their arm muscles Brain Communicator (source : Neural Signals) : requires 10-hr surgery Implanting chips in the parietal cortex might yield unexpected side-effects. Suppose you planned to shake your boss's hand, but thought transiently about slapping him in the face. The slap could happen. Training would soon rule out unwanted responses. And the ideal brain-chip would tap into many different brain regions, coordinating planned actions with instructions for movement. But there are many hurdles to overcome before neural prosthetics become a reality. Current chips function for up to a year and are connected to a computer by wires. The next generation will need to be longer lasting and wireless. Normal and spinal-injured human patients could move a cursor on a computer screen by controlling their own mu and beta rhythms in EEGref. The level of control displayed in this experiment far surpasses that of a similar 1994 studyref : this advance could be attributed in part to improvements in signal processing, but mostly to a new adaptive algorithm that adjusts the EEG features on which it focuses based on the user's past performance. The P300 component of event-related brain potentials (ERP)ref can be harnessed to help a BCI to identify which of 36 characters and symbols displayed on a screen a disabled user has selectedref : this system generates just 7.8 characters per minute with 80% accuracyref. And, like their implantable counterparts, EEG-based methods can be cumbersome, so widespread adoption will likely require wireless technologies : P300 BCI can be implemented in a device the size of a Palm Pilot. Proponents of invasive technologies argue that noninvasive scalp recordings are surrogates that do not actually read motion intent from neurons. Syed has grown snail neurons on a silicon chip and induced them to form a network whose activity was manipulated at the single-cell level through the chipref. A capacitor located underneath one cell induces activity in that cell, while a transistor attached to the chip detects electrical activity in a second cell, providing evidence that the chip can "talk" to the cell and vice versa. That is a critical step for a successful interfacing of electronic devices with the brain cells, whereby the machine talks to the brain and the brain can talk back to the machine : Syed currently is developing chips interfaced with 10,000 to 16,000 neurons that can be used to study how various stimuli affect neural circuits. At the University of Florida, biomedical engineer Thomas DeMarse cultures rat neurons on 60-channel multielectrode arrays that, like Syed's, can be used both to record from and stimulate the cells. DeMarse recently garnered considerable media attention by interfacing his system with an F-22 fighter jet simulator and "training" the cells to manipulate the plane. At the University of Washington in Seattle, Tom Daniel's team implants small computer chips in the hawk moth, Manduca sexta, to study how the insect's nervous system controls flight. Computer scientists have created a hat that can read your thoughts. It allows you to stroll down a virtual street. All you have to do is think about walking. Called a brain-computer interface, the device detects activity in certain brain areas linked to movement, and uses the signals to mimic that movement in a virtual world. The technology could one day help paralysed patients to move robotic arms, or help sufferers of motor neuron disease to type out words on a virtual keyboard. By picking up on these bursts of nerve activity, the computer can decide whether you are thinking about moving your hands or feet, and react accordingly. The technology detects brain waves by using electrodes placed at strategic points on the scalp; they are positioned over brain areas known to be involved in moving specific body parts. The computer can then distinguish between signals corresponding to different types of movement. Previously, accurate detection of local brain activity has required electrodes to be implanted in the brain. This technique has allowed recipients to control robots and even send e-mails. The new device, presented at the International Society for Presence Research 2005 technology meeting in Londonref, achieves a similar feat using non-invasive methods. The team tested their creation by asking participants to navigate a virtual-reality studio called the Virtual Cave. Test subjects sit in a square studio wearing 3D goggles, which project a scene such as a street, complete with pedestrians and buildings. The computer then chooses a task for the participant: either walking forwards or moving their hands. It tells the user what to do through sound cues. If the person is asked to think about walking, and they do so in a way that can be picked up by the cap, the virtual character steps forwards. If they fail, the character stays still. When asked to think about moving their hands, successful volunteers are rewarded by staying still. Failure leads to punishment: their character takes a step backwards. One of the world's best-trained users is Doris Zimmerman, a student who has worked extensively with the team in Austria. She was flown in to help with demonstrations at the conference. As she sits in front of the Virtual Cave's 2D screen, we watch her effortlessly glide down a high street. However, it's not as easy as it looks and 5 hours can be required to learn it. It could even enable stroke patients to regain movement by allowing them to 'exercise' their brain's motor centres. And strengthening the mind might lead to better motor controlref. Web resources : UCL computer science Guger Technologies Technology news
peripheral-machine interface (PMI)	amputees and persons with intact CNS but weak muscles	motors, i.e., prosthetic handref
hybrid brain-machine interface (HBMI)	spinal cord-injured persons with intact limb muscles	muscles, i.e., direct brain control of FreeHandref
computer-brain interface (CBI)	Parkinson's disease	musclesref

Neuroscientists have created a computer game based on table tennis that people can play using nothing more than the power of their minds. It is hoped that the technology will one day train people to generate neural signals that could control a wheelchair or communication device. Each 'brain pong' player lies in a functional magnetic resonance imaging (fMRI) machine, usually reserved for medical brain scans. After a short period of training, the players are able to make their ping-pong bat move up and down the screen by concentrating on specific thoughts. The technique can measure specific areas of the brain with millimetric accuracy, and most subjects proved adept at switching thoughts 'on' and 'off' after just three 45-minute training sessions. Sophisticated data analysis software makes the system responsive enough for two players to compete in real time. The specific method of training varies from subject to subject : one has to find the area of the brain that the subject can control best
Web resources :
• Rainer Goebel
• The Story of Pong
• Play 'Radial Pong'
• Human Subjects play Mind Games
• blood substitutes / artificial blood : although transfusion of donor blood is a routine and sage procedure, there are several reasons for developing blood substitutes :
• a greater need for blood can be predicted as growing numbers of elderly patients needing blood-intensive surgery such as hip repairs or replacements strain the existing donor supply
• human RBCs have exacting storage requirements designed to prolong clinical effectiveness and to reduce the risk of bacterial contamination. This substantially limits the availability of blood at disaster sites or on the battlefield.
• platelet substitutes :
• fibrinogen adsorbed on heat stabilised albumin microcapsules of defined size (Synthocytes™) (source : Quadrant Healthcare plc) for the prevention and treatment of thrombocytopenia^{ref1, ref2, ref3}
• infusible platelet membranes (IPM) (Cyplex^®) (source : Cypress Bioscience) prepared from outdated human platelets^ref
• artificial plasma
•  (solurce : Genzyme)
• replacement of erythrocytes : donor blood shortages make blood substitutes attractive for the short-term replacement during surgery. An ideal blood subsitute should :
• be able to transport oxygen
• require no cross-matching or compatibility testing
• be suitable for long-term storage (preferably at room temperature)
• be able to survive in the circulation for several weeks (the intravascular "dwell" time) before being cleared by the kidney : usually half-life is dose-dependent
• be free of side effects (usually are reversible)
• be more amenable to sterilization to remove infectious pathoges
• not only transport but also effectively deliver oxygen to tissues
Types of blood substitutes :
• hemoglobin-based oxygen carriers (HBOCs) : a cell-free solution of hemoglobin (so that compatibility testing is not required) can be used as a blood substitute because hemoglobin maintains its ability to transport oxygen outside of the RBC. It can be sterilized by ultrafiltration and low heat to inactivate infectious agents, a strategy that is not possible with RBCs.
• human hemoglobin : the source could be outdated donor blood (RBCs that have exceeded the approved storage period), but the limited supply of human blodd has compounded difficulties in developing a human-derived HBOCs. Genetically engineered bacteria (e.g. Escherichia coli) to produce a recombinant source of human hemoglobin would also eliminate the concerns about diseases transmission.
• Hemolink^® (source : Hemosol) : used for heart surgery, half-life 18-20 hours, shelf-life 1 year refrigerated, side effects : vasoconstriction, jaundice
• rHb 1.1 (Optro^®; source :  Somatogen and Eli Lilly) is a genetically engineered variant of hemoglobin Presbyterian, with modifications to decrease its oxygen affinity, produced by Escherichia coli. Intramolecular cross-linking of the tetramer made rHb 1.1 similar in structure to DCLHb
• pyridoxalated hemoglobin polyoxyethylene (PHP)
• source : Curacyte
• polymerized stroma-free hemoglobin (poly-SFH-P) (PolyHeme^®; source : Northfield Laboratories) : used for trauma and urgent blood loss, half-life 24 hours, shelf-life 1 year refrigerated, no side effect reported
• HemoZyme^® (source : Synzyme)
• bovine hemoglobin (Bos taurus) : more readily available (and cheaper) source. It does not have 2,3-DPG, resulting in a P₅₀ of about 30 mmHg both inside and outside the RBC (similar to that of the intracellular native human hemoglobin). In addition, once stripped of all other bovine proteins, bovine hemoglobin is not recognized by the human immune system as foreign. One potential obstacle is the fear that it could harbor the bovine BSE PrP^Sc.
• HbOC-201 (Hemopure^®; source : Biopure), used for elective surgery, half-life 24-36 hours, shelf-life 2 years at RT, side effects : vasoconstriction, transient increase in liver and pancreas enzymes
• worm hemoglobin : hemoglobin from Arenicola marina (a.k.a. lugworm) is 50 times larger thann human hemoglobin and cannot damage kidneys
Problems with these HBOCs included :
• survival times in the circulation < 6 hours (in solution the hemoglobin tetramer readily dissociates into monomers and dimers that are quickly eliminated from the blood stream by glomerular filtration and uptake by the reticuloendothelial system in the kidneys). Integrity of the hemoglobin tetramer can be achieved by chemically modifying hemoglobin :
• specific covalent chemical cross-bonds between polypeptide chains prolong intravascular dwell time of up to 12 hours
• treatment with 3,5-dibromosalicyl fumarate => diaspirin cross-linked haemoglobin (DCLHb) (Hemassist^®; source : Baxter Healthcare) has been used in cardiac and orthopaedic surgery, and for resuscitation of traffic accident victims. It is a DCLHb tetramer made from outdated human blood : it has the advantages of a shelf life of approximately 9 months frozen and 24 hours refrigerated. Its intravascular half-life is limited to 2-12 hours and is dose-dependent.
• treatment with bifunctional cross-linking agents, such as o-raffinose or glutaraldehyde, that target specific amino groups and polymerize the hemoglobin molecule. These reagents produce polyhemoglobin, composed of 4 to 5 hemoglobin molecules, which varies in molecular size and configuration and has intravascular dwell time of up to 24 hours
• conjugation to a variety of larger molecules such as dextran, polyethylen glycol (PEG) (e.g. Hemospan^®; source : Sangart, Inc.), or polyoxyethylene, retarding the rate at which it is cleared from the circulation. In this instance, the intravascular dwell time can be extended to 48 hours
• liposome-encapsulated hemoglobin (LEH) has been found to be an effective oxygen carrier, without the adverse effects of vasoconstriction. The liposome encapsulation appears to increase plasma retention time; however, adverse immune interactions occur with the liposome. This product has the advantage of being freeze-dried and stored at room temperature.
• abnormally high oxygen affinity (without 2,3 bisphosphoglycerate (2,3 BPG) stroma-free hemoglobin has a P-50 of 12-14 mm Hg instead of 26.5 mm Hg, not allowing for the adequate release of oxygen to the tissues. Aeveral to decrease the avidity of hemoglobin to oxygen include the addition of organic phosphate to serve the function of 2,3 BPG and adenosine triphosphate
• hemoglobin (like other plasma proteins) has a colloidal osmotic effect and hence cell-free hemoglobin acts as a plasma expander because the colloidal osmotic pressure it exerts alters the intravascular volume by more than the volume transfused (on the other hand RBCs exert little if any colloidal osmotic pressure) => clinical side effects such as malaise, abdominal pain, hemoglobinuria, and renal toxicity
• some hemoglobin solutions also have vasopressor effects, that is, they increase blood pressure and decrease cardiac output. Several studies have indicated that this vasopressor effect is partly attributable to the ability of cell-free hemoglobin to penetrate the lining of the blood vessels and to scavenge NO^., a cellular chemical messenger which stimulates blood vessel relaxation. Although this vasopressor effect is undesirable for most applications (it can limit circulation to oxygen-starved tissue), it may turn out to be clinically advantageous for treating a small subpopulation of patients with septic shock who suffer from an uncontrollable decrease in blood pressure. Baxter is working on rHuHGB that doesn't scavenge NO^..
New HBOCs under development include polyhemoglobin linked to antioxidant enzymes such as SOD and catalase in an effort to minimize ischemia-reperfusion injury (IRI). In addition, some groups are trying to package human hemoglobin in artificial RBCs made from biodegradable polymer nanocapsules or lipid vesicles.
• perfluorocarbon (PFC) emulsions (PFCE) ("blue blood") are emulsions of synthetic fluorinated hydrocarbons : for religious reasons, certain groups of people (e.g. Jehovah's Witnesses) are unable to accept transfusions of either donor blood or human and animal proteins such as hemoglobin. For these patients, fluorocarbons - molecules that are structurally similar to hydrocarbons except that hydrogen atoms are replaced with fluorine atoms - may be their only option if a blood transfusion is required. Perfluorocarbon liquids have an excellent capacity for carrying O₂ and CO₂ without actually binding to these gases : O₂ readily dissolves in the chemically inert perfluorocarbon liquid and can be easily extracted by O₂-deprived tissues (also used to overcome tumor hypoxia during cancer radiotherapy and cancer chemotherapy). Perfluorocarbons are not miscible with aqueous solutions and must be prepared as emulsions (containing particles with a diameter of approximately 0.2 mm, capable of entering the microcirculation) before they can be used as blood substitutes. The O₂-loading capacity of perfluorocarbons is linearly related to P_O2. in equilibrium with the emulsion. Thus, at a given P_O2, hemoglobin binds significantly more O₂ than can be dissolved in the perfluorocarbons. One perfluorocarbon, Fluosol DA, has been approved by the FDA as a blood substitute for heart surgery: the fully oxygenated perfluorocarbon is infused at the time of percutaneous transluminal coronary angioplasty (PTCA) / percutaneous coronary intervention (PCI) / percutaenous coronary revascularization to provide oxygen delivery during the surgical procedure. Even though the perfluorocarbon reduced cardiac trauma and pain during surgery, its use has never been fully embraced by physicians. Through partial liquid ventilation of the lungs, perfluorocarbons have been successfully used to provide O₂ to premature infants with severe respiratory distress syndrome
• mixture of perfluorodecalin (the carbohydrate decalin (C₁₀H₁₈) in which fluorine atoms replace hydrogen atoms) and perfluorotripropylamine emulsified with Pluronic F-68 (Fluosol-DA^® ; source : Green Cross Corporation of Japan), 20% infusion. Ultimately, this product was ineffective at significantly improving oxygen delivery in the setting of acute hemorrhage. Other shortfalls of Fluosol-DA included a short effective intravascular half-life, temperature instability, low oxygen-carrying capacity, and a poor shelf life. Its major adverse effects included acute complement activation, uptake by the reticuloendothelial system, and disruption of normal pulmonary surfactant. Many of these effects were determined to be caused by Pluronic F-68. Fluosol-DA was approved in the United States for use only during coronary angioplasty; however, because of improvements in angioplasty techniques and the shortfalls of Fluosol-DA, the Green Cross Corporation ceased manufacturing this product in 1994.
• mixture of perfluorooctyl bromide (PFOB) / perflubron and perfluorodecyl bromide emulsified with egg yolk lecithins (Oxygent^® ; source : Alliance Pharmaceutical Corp.) is in stage II/III clinical trials in the USA for general surgery, intravascular half-life 24-48 hours (dose-dependent), shelf-life 2 years refrigerated at 2-8° C, side effects : slight fever, thrombocytopenia. This compound is more stable at room temperature than Fluosol-DA. The oxygen-carrying capacity of Oxygent is 4-5 times greater than that of Fluosol-DA, making this compound more clinically useful in the setting of acute hemorrhage. However, a high fraction of inspired oxygen is required for the compound to be effective
• Neo-PFC
• PHER-O2 (source : Sanguine Corporation) is a second-generation formulation of Fluosol^® designed to overcome some of the deficiencies of the original product; i.e., need for frozen storage, low (20%) PFC content and short intra-vascular residency time
Web resources :
• American Association of Blood Banks (AABB)
• Bloodless Medicine Research (BMR) by  Lelio Mario Sarteschi M.D.
• Bloodless Medicine & Surgery Institute (BMSI)
• NoBlood.com - The Bloodless Medicine and Surgery Network
• Hemo Concepts
• Physicians and Nurses for Blood Conservation (PNBC)
• Artificial Cells & Organs Research Centre at McGill University
• International Society for Artificial Cells, Blood Substitutes &  Biotechnology (ISABI)
• Other companies :
• Perftoran
• Synthetic Blood International, Inc.
• Sangui BioTech International, Inc.
• Journals :
• Artificial Cells, Blood Substitutes & Biotechnology
• artificial saliva / saliva substitute : a solution in distilled water, used to lubricate the oral tissues in xerostomia
• ipromellose
• polyvinylic alcohol
• Optimoist
• Saliment
• hydroxy-propyl-methyl-cellulose (HPMC) containing artificial saliva
• carboxy-methyl-cellulose (CMC) based saliva substitute
• mucin-containing saliva substitute
• xanthan gum-based saliva substitute
• artificial tears / aqueous tear substitute / viscosity agents to treat xerophthalmia
• lubricating ointments / lubricants
• white petrolatum
• mineral oil
• liquid or alcohol lanolin
• cellulose polymers
• carboxymethylcellulose
• hydroxyethyl cellulose
• hydroxypropyl cellulose
• hydroxypropyl methylcellulose
• methylcellulose
• polyvinyl alcohol
• polyethylene glycol
• mineral oil
• glycerin
• dextran
• sodium hyaluronate 0.1%
• ocular prosthesis : an artificial eyeball
• Snellen's reform eye : an artificial eye composed of 2 concavoconvex plates with an empty space between.
• odontokeratoplasty
• intraocular lenses (IOL)
• silicone IOL
• SI-40NB
• sharp-edged
• ClariFlex(R), AMO
• sharp-edged hydrophilic acrylic IOL
• Sensar(R) 40e, AMO
• SC60B-0UV
• AcrySof(R), Alcon Laboratories
Side effect : posterior capsule opacification (PCO).
• vitreous substitutes
• nonexpansile gases
• air
• Ar
• CO₂
• He
• Kr
• N₂
• O₂
• Xe
• expansile gases
• sulfur hexafluoride (SF₆)
• octafluorocyclobutane (C₄F₈)
• perfluoromethane (CF₄)
• perfluoroethane (C₂F₆)
• perfluoropropane (C₃F₈)
• perfluoro-n-butane (C₄F₁₀)
• perfluoropentane (C₅F₁₂)
• silicone oil / polydimethylsiloxane : a long-chain silicone polymer with a viscosity of 5000 to 5400 centistokes, injected into the vitreous to maintain retinal tamponade in the management of complicated retinal detachment
• nonfluorinated silicone oils [ (CH₃)₃SiO[(CH₃)₂SiO]_nSi(CH₃)₃ ]
• fluorosilicone [ (CH₃)₃SiO[C₃H₄F₃)(CH₃)SiO]_nSi(CH₃)₃ ]
• "high-tech" silicone oils [ (CH₃)₃SiO[(C₆H₅)(CH₃)SiO]_nSi(CH₃)₃ ]
• retinal implants : a bionic eye that allows blind people to see has now got a protective coat of diamond that should significantly improve its performance. The silicon chip retinal implant is being developed by Second Sight, a company based in Sylmar, California, along with a consortium of university researchers. The device needs a hermetic case to prevent it from reacting with fluids in the eye. The approach until now has been to lock it in a big waterproof can, but it's very big and bulky, so researchers have developed an ultrananocrystalline diamond (UNCD) film that is guaranteed to be safe, long-lasting, electrically insulating and extremely tough. The coating can also be applied at low temperatures that do not melt the chip's microscopic circuits. The UNCD film is the first coating to meet all the necessary criteria for the implant. The tiny diamond grains that make up the film are about 5 nm across. They grow from a mixture of methane, argon and hydrogen passing over the surface of the 5-mm² chip at about 400°C. Xiao and his colleagues have already tested the implants in rabbits' eyes, and saw no adverse reaction after 6 months : the results were presented on 1 April 2005 at the Materials Research Society meeting in San Francisco, California. A healthy retina contains rod and cone cells that convert light into electrical impulses, which fly to the brain through the optic nerve. But for millions of people with diseases such as retinitis pigmentosa or macular degeneration, these cells do not work properly. The retinal implant bypasses these diseased cells by electrically stimulating healthy cells that sit beneath them at the back of the eyeball. The patient 'sees' using a pair of glasses carrying a tiny video camera that sends digitized images to the implant using radio waves. The first human trial of Second Sight's artificial retina has been running since 2002, and it has enabled a formerly blind patient to distinguish between objects such as cups and plates, and even to make out large letters. But with only 16 electrodes, the device does not allow the patient to see a clear picture. For that, thousands of electrodes are needed on the same size of chip, making it even more delicate. In the first trial, the electronics package was separated from the electrodes and implanted behind the patient's ear because its casing was so bulky, explains Greenberg. The team's goal is to integrate everything into a single unit that fits neatly into the eye. A UNCD coating could be equally useful for other implantable devices, such as biosensors to monitor a patient's health. They've managed to create a diamond film that is of considerably higher quality than other methods have managed, but the ultimate potential of these devices will only be told in long-term trials. Second Sight is planning clinical trials of a 60-electrode device this year, but it may be several more years before the diamond-coated chip is used in humans
• heart prostheses
• pace-makers
• ventricular reshaping^ref : lessons learned from ventricular remodeling procedures have shown that Laplace mechanics, whereby mural tension is related to ventricular diameter, may be beneficially applied to the left ventricle (LV). Recently developed devices, predicated on the Law of Laplace, are directed at interrupting the heart-failure cascade without removing functioning myocardium.
• partial left ventriculectomy / left ventricular chamber reduction surgery
• endovascular patchplasty
• device-based external ventricular reshaping / passive containment surgery ^ref
• dynamic cardiomyoplasty (CDM) using the latissimus dorsi muscle implanted all around the heart and stimulated by electrodes placed among muscle bundles, becoming spontaneous within 6 weeks via a transformation of type II (fatigueable) muscle fibers into type I (not fatigueable) muscle fibers. Dynamic cardiomyoplasty has been performed in over 1000 patients worldwide but due to limited success the procedure was never been adopted as an alternative approach for the surgical therapy of heart failure. However, observations in these patients showed that the nonstimulated or fibrotic transformed latissimus dorsi by itself led to an improvement of heart failure symptoms. These findings stimulated animal experiments with so-called passive cardiomyoplasty devices. In several animal models, the progression of heart failure could be stopped, and even reversed remodeling could be demonstrated. Several different devices have been developed and tested in animal models. Diabetes-induced alterations in latissimus dorsi muscle properties impair effectiveness of dynamic cardiomyoplasty in rats^ref.
• Myosplint^® (source : Myocor, Inc., Maple Grove, MN) : passive implantable device that uses transmural tension members to bisect the dilated LV to create a bilobed LV with decreased mural tension in each cavity^ref.


• CorCap^® cardiac support device (CSD) (source : Acorn Cardiovascular Inc., St. Paul, Minn) is a polyester mesh-like device that is surgically implanted around the heart. The device is designed to provide circumferential myocardial wall end-diastolic support,  reduce ventricular wall stress and myocyte stretch, improve function, and reverse cardiac remodeling. The CorCap device has been implanted worldwide in > 130 patients with dilated cardiomyopathy (idiopathic or ischemic), with or without concomitant cardiac surgery^{ref1, ref2}. It has already passed a successful clinical feasibility study and already has EMEA approval. However, the final evaluation of two multicenter trials has to be awaited to assess the future role of this device in the treatment of heart failure^ref.


• mechanical circulatory support (MCS) in patients presenting with cardiogenic shock waiting for heart transplantation. In general, 2 categories of blood pumps can be distinguished:
• displacement pumps move a certain amount of blood by the movement of a flexible membrane. This movement requires an extensive installation: artificial ventricles, tubing, motors, pneumatic systems and driving consoles
• pneumatically driven
• electrically driven
• rotary blood pumps are well suited for miniaturisation and endovascular implantation. They can be either
• axial : Hemopump, MicroMed DeBakey VAD, Jarvik 2000, HeartMate II, Streamliner, Impella, Berlin INCOR I, Valvo pump, and IVAP^ref
• diagonal
• radial
• ventricular assist device (VAD) / auxiliary ventricle / booster heart : an implanted pumping mechanism designed to assist a ventricle of the heart in maintaining normal output, rate, and blood pressure. While "resting" during VAD support, damaged cardiac muscle starts to repair itself and to contract with more vigor. The benefit of a VAD versus a TAH is that the natural heart remains in place-if the VAD is stopped or removed, the patient's heart can still support the circulation. Clinical experience has demonstrated that once a damaged heart is "rested" through VAD support and eventally treated for several months with b₁-agonists, the heart can repair itself and its function improves. In a few cases, the VAD was removed and the patient no longer needed a transplant. The goal is for wider application of VAD support so that heart failure patients are supported for weeks or months until cardiac damage has been repaired sufficiently such that a transplant is not necessary. Design of the VAD began as early as 1963 but did not progress rapidly until the 1990s. Since then, thousands of patients have been successfully supported, sometimes for years
• right ventricular assist device (RVAD) for right ventricular failure (RVF)
• left ventricular assist device (LVAD) or system (LVAS) supports the left ventricle, the locus of the most critical heart damage in left ventricular failure. Blood flows from the left atrium through the left ventricle and the pump inflow valve into the LVAD, which then pumps the blood into the ascending aorta. With a LVAD, the right ventricle benefits from reduction of left atrial and pulmonary arterial pressures and the heart can start to repair itself
• biventricular assist device (BiVAD / BVAD) or system (BVS) for congestive heart failure (CHF)
• extracorporeal or paracorporeal VAS are available for RVAS, LVAS, or BVAS
• Toyobo VAS^®
• Zeon VAS^®
• Medos-HIA system^®
• Berlin Heart^®
• Medtronic Bio-Medicus Pump^®
• Pierce-Donachy pediatric system^®
• percutaneous applicable cardio-pulmonary support (pCPS)^®
• Thoratec Ventricular Assist Device (VAD) System (VAS) (Thoratec Laboratories, Pleasanton, CA) is a paracorporeal pump that can provide univentricular or biventricular assistance for patients with heart failure. The system consists of a prosthetic ventricle that has a blood-pumping chamber of Thoralon / BPS-215M^® (Thoratec Laboratories) polyurethane ...


..., cannulas for univentricular or biventricular support ...

..., and either a hospital-based pneumatic drive console ...

... or a portable battery-powered drive unit^ref.

For biventricular assistance, 2 pumps are used.

The Thoratec voluntary registry indicates that, as of May 2000, this system had been implanted in 1,376 patients, mainly for bridging to transplantation (828 patients) or postcardiotomy support (195 patients); the remaining 353 patients received a hybrid configuration of the device or had incomplete information, so they are not included in this analysis. In the 828 bridge-to-transplant patients, the Thoratec system provided biventricular assistance in 472 cases, left ventricular assistance in 326 cases, and right ventricular assistance in 30 cases for up to 515 days. During the support period, the cardiac index increased significantly from 1.4 +/- 0.8 L/min/m² to 3.0 +/- 0.5 L/min/m² (with biventricular assistance and left ventricular cannulation). 60 percent of the 828 patients underwent transplantation, and the posttransplant survival rate was 86%. In the 195 patients who needed postcardiotomy support, VADs were used for up to 80 days for cardiac recovery. Thirty-eight percent of the patients were weaned from the VAD, and 59% of the weaned group were discharged from the hospital. In addition, 49 postcardiotomy patients were considered for transplantation; of these, 32 received a transplant and 23 were discharged. Patient mobility is being improved by the use of a portable driver. The Thoratec VAD is suitable for a wide range of applications, and efforts are underway to facilitate patient mobility and allow hospital discharge. An intracorporeal version of the VAD, which is currently under development, will help achieve these goals^ref.
• implantable or intracorporeal ventricular assist device (IVAD)
• Novacor LVAS^® (source : Baxter) : pulsatile, long-term VAD commonly used as a bridge to transplantation


• HeartMate™ LVAS (Thermo Cardiosystems Inc., Woburn, MA) (the most commonly used VAD) : starting initially with a pneumatic actuated pusher plate pump, clinical use of the HeartMate I began in 1986. In 1990, electric motor-actuated versions of the HeartMate I began to be used clinically. Presently, the HeartMate I has been implanted in some 2,300 patients worldwide, and this LVAD is a standard by which all others are currently measured.
• Thoratec HeartMate^® Implantable Pneumatic Left Ventricular Assist System (IP LVAS) [1000 IP]
• HeartMate LVAS IP^®
• TCI HeartMate vented-electric system (VE)^®



• Novacor N100^® wearable left ventricular assist system)
It is a rotating torque motor and cam system that displaces 75 cc of blood from the ventricle into the aorta. The control system can increase or decrease the pump rate to match the demand. The surfaces that make contact with blood are textured so that an adherent layer of blood cells settles on the surface, enabling blood to flow smoothly. Blood is directed through the pump by inflow and outflow valves made of pig tissue. In the Cleveland Clinic experience, the incidence of emboli or stroke is about 2%, using only aspirin as an anticoagulant.
• a new type of IVAD in which rotary dynamic pumps produce a continuous nonpulsatile blood flow and no artificial valves are required is currently in clinical trials. The entire mechanism sits in the ventricle immersed in blood, an environment hostile to bacteria. In some situations, patients with this new VAD have a normal cardiac output of 5 to 6 liters/min, but no palpable pulse of measurable blood pressure! There was concern that this would cause physiological abnormalities, but experience with animal models and early clinical results suggest that the difficulties may have been overestimated. These continuous-flow devices are much smaller and simpler than the pulsatile pumps and thus fits the majority of adults and children. They may also be less expensive. Most current designs use highly polished titanium surfaces that appear to be compatible with blood, at least for the short resistance times during which blood is in contact with the pump. As a partial assist VAD that elevates the toal cardiac output of a weak heart elevates the total cardiac output of a weak heart closer to the normal range, these devices show tremendous potential. Prototypes of the continuous flow VAD include
• Hemopump^® (Medtronic, Inc, Minneapolis, MN) was conceived in 1975 and designed in 1982 as a temporary, extracorporeal cardiac assist system. Although it has been used clinically in Europe, it is not currently available in the United States. In vitro and in vivo testing of the Hemopump began in 1983. Clinical investigations have included studies of patients in cardiogenic shock, Hemopump-supported coronary artery bypass operations in Sweden, and European studies of percutaneous transluminal coronary angioplasty (PTCA) with Hemopump support. The Hemopump has demonstrated positive hemodynamic effects in patients. Laboratory and clinical studies have shown that the nonpulsatile axial flow generates flows of up to 4.5 L/min while maintaining adequate perfusion of other organs. In Europe, hemopumps have been used successfully to support coronary bypass and PTCA. The Hemopump system is simple, inexpensive, and well tolerated by the blood elements. Moreover, its design allows flexibility in supporting patients during cardiopulmonary bypass (in lieu of conventional techniques) and high risk angioplasty, as well as in rescuing patients with low cardiac output^ref
• Jarvik 2000 FlowMaker LVAD^® (Jarvik Heart Inc., New York, NY) is a larger, longer-term, electrically powered, axial-flow blood pump that provides continuous flow from the left ventricle to the descending thoracic aorta. Because of its small size, this device can be placed within the left ventricle, and no inlet cannula is needed. The continuous blood flow eliminates the need for valves, an internal compliance chamber, or an externalized vent. The system consists of a blood pump, 16-mm outflow graft, percutaneous power cable, pump-speed controller, and direct-current power supply. The blood pump is simple in design, its single movable component being an impeller located in the center of the titanium housing. A brushless direct-current motor contained within the housing creates the electromagnetic force necessary to rotate the impeller. The impeller consists of a neodymium-iron-boron magnet suspended by 2 ceramic bearings. On the impeller’s outer surface are 2 titanium hydrodynamic blades. All the blood-contacting surfaces within the pump are made of smooth titanium. Blood flow is directed through the outflow graft by stator blades located near the pump outlet. The controller and battery are worn on a belt or are carried in a bag. The vaned impeller rotates in response to the electromagnetic force created by the motor, which is contained within the pump housing. The impeller is suspended by ceramic bearings (not shown). Outflow stator blades (not shown) direct blood flow through the pump’s outflow conduit.



The motor receives power from the external controller through a series of wires that are contained in a silicone tube covered with Dacron. The motor speed is manually adjusted and is regulated by a pulse-width-modulated, speed-control circuit. Lead acid or lithium ion batteries provide the system’s 12-volt power supply. The pump’s operating range is 8000 to 12 000 rpm; under optimal physiological conditions, these speeds can generate flows of up to 6 L/min. The normal power consumption is 3 to 7 watts. The pump’s speed is adjusted in 1000-rpm increments until minimal flow is ejected through the aortic valve. In case of a system malfunction, the controller provides both an aural and visual alert. Ambulatory patients can maintain the system’s external equipment and change the batteries as needed. The pump is implanted through a thoracotomy incision with the aid of partial cardiopulmonary bypass (CPB). The femoral artery and vein are exposed for CPB cannulation. A left thoracotomy is then made in the fifth or sixth intercostal space, and the heart and descending thoracic aorta are exposed. The aorta is partially occluded while the outflow graft is anastomosed to the aorta. The femoral vessels are then cannulated and CPB is begun. Ventricular fibrillation is induced, and a circular knife is used to create an opening in the left ventricle. A silicone/polyester sewing cuff is sewn to the apex of the heart with pledgeted sutures. The power cable is tunneled subcutaneously across the abdomen from left to right just below the diaphragm and exits the skin at the right anterior portion of the abdomen. The pump is inserted into the left ventricle and is secured with cotton tape around the cuff and pump housing. The pump’s outflow graft is anastomosed to the graft previously placed on the aorta. The heart is then defibrillated, and air is removed from the left ventricle, pump, and graft. As CPB is gradually discontinued, the pump is turned on. Pulmonary vasodilators and inotropic agents are used as necessary to support right-sided cardiac function. Intraoperatively, hemodynamic assessment is performed with transesophageal echocardiography, a pulmonary artery catheter, an arterial pressure line, a pressure line to the left ventricle, and an ultrasonic flow probe on the pump’s outflow graft. Hemodynamic values are recorded at each pump speed, and the optimal speed is determined. Flow through the pump can be calculated accurately against varying mean pressures^ref. The ultrasonic flow probe is removed before the thoracotomy incision is closed. In the early postoperative period, hemodynamic function is assessed with an arterial pressure line, a pulmonary artery catheter, and transthoracic echocardiography. Once all the monitoring lines have been removed, hemodynamic assessment is based on echocardiography and routine evaluation of vital signs. Postoperatively, the goal is to maintain pump flow at the lowest level compatible with a normal cardiac index and NYHA class I status. Hemodynamic and echocardiographic studies are performed routinely to determine the proper pump-speed setting. During these tests, the pump speed is increased in 1000-rpm increments over the usual operating range of 8000 to 12 000 rpm, after which the pump is turned off for up to 5 minutes. Serial echocardiographic studies are performed at 24 hours, 1 week, 1 month, and every 3 months thereafter until support is terminated^ref.
• LionHeart LVD 2000^® (Arrow International, Reading, PA) left ventricular assist device is the first fully implantable system designed for destination therapy (ie. no heart transplantation required)^{ref1, ref2}. It was first implanted on October 26 1999 in Germany. In 2001 the first LionHeart was implanted in Italy at Pavia Hospital. As for AbioCor TAH, there are no cables connected trough the skin and the internal battery is continuously recharged via a battery waist which conducts energy to an internal serpentine


• Kantrowitz CardioVAD (KCV)^® (LVAD Technology, Detroit, MI) is an implantable IABP designed to provide permanent mechanical assistance that can be activated intermittently, require no anticoagulation, allow for treatment of CHF and potential myocardial recovery, and not pose an increased risk of cerebrovascular accidents (CVA). It is an electrically powered, pneumatically driven circulatory assist device which provides diastolic augmentation and systolic unloading to the failing heart. It consists of a 60cc-pumping chamber (a), a percutaneous access device (PAD) (b), and an external controller (c).


The pumping chamber, is surgically implanted in the descending thoracic aorta with the patient on cardiopulmonary bypass. Its physiologic function is analogous to that of the intra-aortic balloon pump (IABP)^ref. A 1x5 cm full thickness segment of skin was obtained from the forearm, under local anesthesia at the bedside. Autologous fibroblasts were cultured from the biopsy specimen for 10 to 14 days and used to coat the percutaneous access device (PAD). Once this procedure was completed, patients were admitted for KCV implantation. Under general anesthesia, a left thoracotomy was performed through the 5th interspace. The aorta was encircled 1, 8, and 16 cm distal to the subclavian (points A, B, C, respectively). Patients were completely heparinized and placed on warm, heart beating cardiopulmonary bypass (CPB) using femoral arterial and venous cannulae. Another arterial cannula was placed at the aortic arch for cerebral perfusion. The aorta was crossclamped at points A and B and incised longitudinally. Removed from the edges were 3-mm strips of the aorta. The superior portion of the KCV was sutured in place with a single layer of 2 to 0 polypropylene running mattress suture. A felt strip was used on the aortic side as a buttress. The crossclamp at B was released and reapplied at point C. Intercostals were controlled with Fogarty catheters. The distal portion of the KCV was sewn to the aorta in a similar technique to the proximal end. The point C clamp was removed and a second layer of sutures used to further secure the KCV. After obtaining hemostasis, 3 epicardial screw-in electrodes (St. Jude Pacesetter, St. Paul, MN) were placed in a triangular pattern 1 cm apart on to the lateral portion of the heart. The device (bladder integrity and electrode sensing) was tested as mechanical support was initiated. This assisted in weaning from CPB. The thoracotomy incision was closed and the patient placed in the supine position. The PAD was then inserted into a subcutaneous pocket in the right upper quadrant and the device connected. Patients were extubated, weaned from inotropes and ambulated as soon as possible. All patients were run with maximum diastolic augmentation with the device set to inflate immediately after the dicrotic notch. Anti-coagulation was not used for the device—1 patient received coumadin for a mechanical prosthetic aortic valve^ref.
• DeBakey VAD^® system (MicroMed Technology, Inc.; Houston) is a miniaturized, electromagnetically actuated, fully implantable titanium axial flow pump weighing 93 g^ref and consisting of 4 parts: a pump, a controller, a clinical data acquisition system (a laptop computer), and a patient home support system (wall power and battery charger). The pump consists of a titanium inflow cannula and apical ring, the housing unit containing the impeller (only moving part) and motor, a Vascutec gelweave outflow vascular graft that exits the pump as an outflow conduit and connects to the aorta, and a percutaneous cable. An integral flow probe placed around the outflow graft measures real-time cardiac output through the graft. The cable from the flow probe and the impeller are bundled into a single cable assembly, which exits the skin of the anterior abdominal wall at a point superior to the right iliac crest. The cable is then connected to the controller. The pump is designed to achieve 5 L/min against 100 mm Hg pressure with a speed of 10 000 rpm. The flow curves, speed, current and power are displayed in a bedside monitor unit (the clinical data acquisition system (CDAS)) that is accessed to make adjustments to the pump speed. A pump motor cable along with the flow probe’s wire exit transcutaneously and connect to the external controller. The latter, consisting of the controller module, battery packs and battery charger, is designed to operate the pump. To facilitate mobility and eventual hospital discharge, the pump can be actuated by 2 12-volt DC batteries for 4 to 6 hours^ref. 2 batteries can be connected to the controller at the same time. The controller can also use the power supplied by the CDAS or the patient home support system. The CDAS is used by the clinician to start or stop the pump, modify the pump speed, and set alarm limits. It displays and also stores the data and serves as a primary power source for the pump. The patient home support system is a small unit that charges 4 batteries at a time and also provides wall power to the controller when the patient is at home. European trials of the DeBakey VAD began in November 1998, and CE Mark certification of the device as a bridge to transplantation was awarded in May 2001. In the United States, clinical trials began in June 2000, and a 20-site Phase III Pivotal clinical trial is expected to conclude early in 2004. As of 4 March 2003, 179 patients at 14 heart centers in 7 countries had been implanted with the device. The longest surviving patient had lived for over 443 days with the VAD in place. Surgical procedure :
• in general, the heart is exposed via standard median sternotomy and full cardiopulmonary bypass support is established with atrio-aortic cannulation. In most instances, implantation proceeds without cardioplegic arrest. Transesophageal echocardiography (TEE) is routinely used to rule out the presence of aortic insufficiency, intracardiac thrombus and/or atrial septal defect (or patent foramen ovale) that may require further intervention. In addition, TEE guides intracardiac deairing, and provides superior imaging of inflow cannula placement, right ventricular function, and left ventricular decompression. Without the need to extend the median sternotomy incision, a small preperitoneal pocket is created to house the pump under the left costal margin. The left ventricular apex is cored out and an apical ring is sewn to the apex. The inflow cannula is inserted into the left ventricular cavity and secured to the apical ring. A small incision is made in the left lower quadrant and the thin driveline is routed transcutaneously and connected to the controller. Next, the outflow graft is tailored to reach the ascending aorta. A partial occluding clamp is placed along the greater curvature of the ascending aorta and the graft is anastomosed in end-to-side fashion using standard suture technique. In difficult reoperative cases, the device can be implanted to the descending aorta via a left thoracotomy. The graft is deaired and the patient is weaned from cardiopulmonary bypass as the device is actuated. Usually, inotropic support for the right heart is used. In some instances, intra-aortic balloon pump support and inhaled nitric oxide are employed^ref.
• a small, extrapericardial, subdiaphragmatic pocket was formed below the rectus muscle. The pericardium was opened. The ascending aorta was cannulated, and then bicaval cannulation from the right atrium was performed. Under cardiopulmonary bypass, while the heart was beating, its left ventricular apex was elevated, and an apical fixation ring was sewn to the apex. The inflow cannula was inserted through the fixation ring into the left ventricle in such a manner that it was angled toward the aortic valve but not the septum or the free wall of the myocardium. The pump cable was threaded out of the body through the anterior abdominal wall, at a point above the right iliac crest. The VAD was placed into the pocket, and the outflow graft was anastomosed to the ascending aorta. Using transesophageal echocardiography, we checked the location of the inflow cannula. After removing the remaining air in the system, we started the pump at a speed of 7,500 rpm. When pump flow was adequate, the patients were weaned from cardiopulmonary bypass^ref.
• HeartMate II (designed to run for 5 to 8 years) (Thermo Cardiosystems Inc., Woburn, MA) is a rotary-pump-based LVAD that uses an axial flow blood pump having blood immersed mechanical bearings. Clinical trials of the HeartMate II were initiated in 2000. It has evolved from 1991 when a partnership was struck between the McGowan Center of the University of Pittsburgh and Nimbus Company. Early iterations were conceptually based on axial-flow mini-pumps (Hemopump) and began with purge bearings. As the project developed, so did the understanding of new bearings, computational fluid design and flow visualization, and speed control algorithms. The acquisition of Nimbus by ThermoCardiosystems, Inc (TCI) sped developments of cannulas, controller, and power/monitor units. The system has been successfully tested in more than 40 calves since 1997 and the first human implant occurred in July 2000. Multicenter safety and feasibility trials are planned for Europe and soon thereafter a trial will be started in the United States to test 6-month survival in end-stage heart failure^ref.
• HeartMate III / HeartMate XVE™ (designed to run for up to 10 years) (Thermo Cardiosystems Inc., Woburn, MA) is structured around a centrifugal blood pump that uses a magnetically levitated rotating assembly. Compared to the HeartMate II, the HeartMate III has the potential for higher overall efficiency. The pump's operating life is not dependent on bearing wear^ref. The pump has been optimized by in vitro testing to achieve a design point of 7 L/min against 135 mm Hg at high hydrodynamic efficiency (30%) and to be capable of up to 10 L/min under such a load. Furthermore, the pump has demonstrated no mechanical failures, low hemolysis (4-10 mg/dl plasma free Hb), and low thrombogenicity during 6 (40, 27, 59, 42, 27, and 49-day) in vivo bovine studies^{ref1, ref2}. Electronics based on a rigid-flex satellite printed circuit board (PCB) arrangement that could be folded into a very compact, dense package were designed, fabricated, and tested. The pump's lower housing was redesigned to accommodate these PCBs without increasing any dimension of the pump except the height, and that by only 5 mm. The interconnect cable was reduced from 22 wires to 10 (two fully redundant sets of 5). An ongoing test of the assembled pump in vitro has demonstrated no problems in 5 months. In addition, a 20-day in vivo test showed only 1°C temperature rises, equivalent to pumps without incorporated electronics at similar operating conditions^ref.
• Thoratec IVAD^® is controlled with the Thoratec TLC-II Portable VAD Driver, which is a small briefcase sized, battery powered, pneumatic control unit. Intracorporeal LVADs and/or RVADs are implanted in a preperitoneal position, with a single small (9 mm OD) percutaneous pneumatic driveline for each VAD. The major advantages of the new IVAD design are size and simplicity. The IVAD weight (339 g) and implanted volume (252 ml) are substantially smaller than current implantable electromechanical LVAD systems. Only the small blood pump is implanted, leaving the more complex control unit external, where it can be serviced and replaced. The versatile design is intended for left and/or right heart support in large or small patients. The IVAD in combination with the TLC-II portable driver will be a viable and attractive alternative to large, implanted electromechanical systems^ref.
• Magnevad LVAD^® : a miniature axial flow LVAD whose first animal implant is scheduled for the fourth quarter of 2003. This is being performed by the George E. Reed Heart Center of Westchester Medical Center and by New York Medical College; both are in Valhalla, NY. This LVAD has new innovations not found in any other turbo pump to minimize thrombus, blood turbulence, flow separation, and the generation of microemboli. The Magnevad is only 25 mL in volume, similar in size to the Micromed & Jarvik 2000 axial flow turbo pumps that have contacting bearings. US Patent 6 527 699 was issued to Gold Medical on March 4, 2003 and World Wide PCT patents are pending. The improvements (patents pending) are designed to minimize flow separation and turbulence, the precursors of microemboli that lodge in end organs. This problem has been largely ignored in the published literature. A new long-term stable miniature ultrasonic position sensor is used for bearing control. It measures the axial position of the rotor to obtain LVAD differential pressure. Differential pressure is used to obtain pulsating flow and automatic physiologic control. The term "fourth generation pump" is being coined for the Magnevad because in addition to being noncontacting, it inherently measures pump differential pressure on which physiologic control can be based^ref.
• Intracardiac Pump LV^® for left ventricular support and the Intracardiac pump RV^® for right ventricular support (source : Impella CardioSystems AG, Aachen, Germany). The Impella pumps are rotary blood pumps of the axial flow type and produce 4.2 L/min at physiological pressure differences and a rotational speed of 32,500 rotations/min. These micropumps can widen the indications of beating heart surgery by sustaining hemodynamic stability and protecting the heart from warm ischemia. The current concept is aimed at bridging a procedure. Therefore, the proof of safe duration of usage has not been extended beyond 6 hours



They are all now in clinical trials. Each of these devices has an axial flow impellers supported on blood-lubricated pivot points. So far, the devices have been implanted with a percutaneous wire that connects the device to an external controller and battery. Nothing prevents the use of a transcutaneous energy transmission system (TETS) system in future versions, although this would add hardware to the implant. The next generation of VAD blood pumps (still being tested in the laboratory) use 3D magnetic suspension of the pump rotor. These pumps address residual concens regarding friction, wear, and the crevice-like geometry of the pivot supports (which trap blood cells), and are predicted to remain reliable for > 10 years. This technology, the prototype of which is hopefully to be launched this year, brings us much closer to the day when small reliable pumps with few complications become as common as pacemakers and heart valves.
In USA LVAS are a destination therapy in patients with end-stage heart failure who, despite receiving optimal treatment, have a life expectancy of < 2 years and are not viable candidates for heart transplantation
Complications : significant infection rates have been reported among LVAD recipients. However, few reports have focused specifically on device infection, its treatment, and the impact of LVAD-related infection on clinical outcome. 46 LVAD-related infections were diagnosed in 38 (50%) of 76 patients who underwent LVAD implantation as a bridge to transplantation. 29 episodes of LVAD-related bloodstream infection (BSI) (including 5 that were cases of LVAD endocarditis) and 17 episodes of local LVAD infection were identified. Diabetes mellitus appeared to increase the risk of BSI among patients with LVAD infection. LVAD-related infection delayed transplantation, as reflected by longer device-support times (a mean duration +/- SEM of 182.8+/-31.1 days, compared with 66.3+/-8.8 days; P<or=.001). Continuous antimicrobial treatment before, during, and after transplantation was associated with fewer relapses than was a limited course of antibiotics (P<.001). A trend for longer hospital stays after receipt of a transplant and increased early mortality was observed in the cohort with LVAD-related infection, although long-term survival was similar to that associated with patients without LVAD-related infection. Posttransplantation invasive vancomycin-resistant Enterococcus faecium (VREF) infection was diagnosed in 6 patients with LVAD-related infection; 4 of these patients died. No VREF infections were identified in patients without LVAD-related infection. LVAD-related infection is common and may require antimicrobial therapy before, during, and after transplantation, but that it does not prevent successful transplantation. However, patients with LVAD-related infect