The Jarvik-7 model has been the most popular device used so far for adequate circulatory maintenance in the absence of a heart. However, its use has mostly been as a bridge and confidence in artificial heart implantation as destination therapy is still an issue, both patients and physicians seem to have similar ideas. Additionally, there may be problems related to the separate drive lines. The thought of carrying a package containing rechargeable batteries and a pneumatic compressor makes the patient think of a dreary life where freedom is severely compromised.
The business history is complicated. Symbion, the company that first had the marketing rights of Jarvik-7, had permission for use only up to 1990. CardioWest Inc. bought the rights and from 1993 they started a trial. At this time the device came to be known as the CardioWest TAH. On completion of the trial, which was primarily designed for a statistical evaluation of the device as a temporary bridge to transplant, CardioWest assumed the name Syncardia to ensure better global representation in patients dying due to end-stage heart failure and the prospect levitation in a matched donor heart is still not on the horizon. Improvisation, design changes and other improvements were never interrupted. Syncardia's total artificial heart was approved as a bridge to transplant in 2004, and one could purchase the Jarvik-7 model from Syncardia Incorporations without any third-party mediation until 2016. The model was available in two sizes - 70 cc for adults and 50 cc for females, young adults and children. Two drives were also produced - Companion - 2 (in-hospital) and the more compact Freedom (for ambulation). However, a private equity firm, Versa Capitals, injected money and bought titular rights when Syncardia faced bankruptcy. Soon after, Syncardia was again acquired by Hunniwell Lake Ventures under its portfolio company, Picard Medical. In 2023, SynCardia filed to become a publicly traded company and is now a Special-purpose Acquisition Company (SPAC). This is the saga of the Jarvik-7 model of the total artificial heart.
Several investigators attempted implantable models of a total artificial heart. The following accounts summarise the notable efforts. Army pitched in with an effort in the '60s. The device. solid (made of plexiglass), compact, working on the principle of fluid amplification, and could maintain a systolic pressure of 60 mm of Hg. Animal experiments proved the feasibility of the product but implantation due to size is not possible because of its size, even though it is compact. The best clinical use was in the quick transportation of wounded soldiers dying in war.
The European experience and research are similar to those pursued in the USA. The Polish developed a pneumatically compressible Jarvik-7-type circulatory assist device, POLVAD-EXT prosthesis, developed by the Foundation of Cardiac Surgery Development, Zabrze, Poland, in 1991. The device is fitted with acoustic sensors, which help in blood volume measurements. The biggest difficulty is that the drive console, which has to be constantly carried with the patient, is voluminous and not fit for ambulatory discharge. The Polvad prosthesis has never been used for destination therapy.
Two people of oriental origin, Kevin K. Cheng, a dentist, teamed with T.M. Kao and his other surgical associates made history by implanting a technologically advanced pneumatic Phoenix-7 Total Artificial Heart (TAH) at the Taiwan TAH Research Center in Tainan. The operation was done on a 46-year-old man, and more significantly, the man underwent a combined heart and kidney transplant during the same procedure.
This is a picture of the Abiocor model, the first fully implantable total artificial heart. The device was conceived as a collaborative work between engineers and medical personnel at Texas Heart Institute, the University of Louisville, and Abiomed Incorporated, Danvers, Massachusetts. The parent company of Abiomed is Johnson & Johnson and Abiocor TAH was presented under the Impella platform. There was a significant difference - an actuator or a movable diaphragm alternatively compressed the membrane-enclosed systemic and pulmonary ventricles. 4 polyurethane valves prevented backflow and ensured forward flow only. Transcutaneous energy transmission ensured the recharging of the batteries required to run a motor drive. An internal lithium-ion battery can power the thoracic unit for half an hour. A transmit TET coil is secured externally over the internal coil with an adhesive dressing for long-term power transfer. The absence of actual pneumatic for drive lines and the wounds reduces the implant's weight and the incidence of complications. The device attained humanitarian device exemption status from the FDA and is implanted in a designated medical unit, provided the unit has the sanctioned certification. Abiocor II is a new hybrid model developed with Pennsylvania State University. Abiomed silently phased out the first design after a feasibility trial with 15 patients in approved centres. Trials are now being planned with this Abiocor II model.
The European experience and research are similar to those pursued in the USA. The Polish developed a pneumatically compressible Jarvik-7-type circulatory assist device, POLVAD-EXT prosthesis developed by the Foundation of Cardiac Surgery Development, Zabrze, Poland, 1991. The device is fitted with acoustic and optical sensors which help in blood volume measurements. The biggest difficulty is the fact that the drive console that has to be carried constantly with the patient is voluminous and not fit for ambulatory discharge.
The Polvad prosthesis has never been used for destination therapy.
Paradoxically the Texas Heart Institute (THI) has never been the centre approved for the implantation of a TAH even though the centre boasted of having the best cardiac surgeons of that time. Despite all, the ventricular assist devices did good clinical and experimental work. In 2011 O.H. Frazier and W. Cohn combined two Heartmate II ventricular assist devices and implanted the gadget into a patient suffering from end-stage heart failure due to amyloidosis. The patient ultimately died due to liver and kidney failure and the combined device, which was still working, was switched off with the party's consent. This was a one-off experiment.
In 2008 Professor Alain Carpentier created a company named Carmat SA dedicated to the creation of an implantable artificial heart covered with a compatible biomaterial for minimising the chances of rejection and clot formation. The main aim is a worthwhile solution for people with end-stage heart failure. The device was named Aeson and a timeline for the clinical trial was announced for 2011 with an expectation that the device would be ready for actual implantation by 2013. The bovine pericardial layering of the internal biological fluid contact area is the notable "Bioskin" and one single large pumping cavity is divided into two by a bipartite wall.
Parts of each atrial wall with intact atrioventricular valves are left behind during the cardiectomy to which Dacron/Teflon cuffs are mechanically attached separately. Circular metallic flanges to which the Aeson prosthesis can be seamlessly attached are on the other end of the cloth cuffs. Two motors are used for driving hydraulic fluids that move blood forward into separate systemic and pulmonary tracts having bovine semilunar valves as in normal hearts preventing backflow. The main disadvantage is the size -- an Aeson prosthesis weighs about 900 gms and can only be fitted into large and obese subjects. Presently the Aeon prosthesis has a CE certification and based on trials, the device can be implanted as a bridge in a suitable patient for 180 days only.
After the invention of the 3-D printer, the thought process of the people in TAH research changed. The new search was for a TAH made with a soft material and smaller size -- the result was a model of a soft artificial heart presented by Nicholas Cohrs and colleagues under the supervision of Professor Wendelin Stark at the functional materials laboratory at Eidgenössische Technische Hochschule (ETH) Zurich University. The pressurised air is used for the forward propulsion of blood. The proposed model has dimensional (weight 390 gms, and volume 180 cm 3³ ) but the 2.5 mm thick silicone partition between the blood and air chambers developed a major breach. Further work is being carried out before the laboratory animal trials.
The year 2024 saw new ideas implemented during the construction and trial of implantable total artificial hearts. Both the magnetic levitation and axial flow technologies when combined can maintain a continuous circulation and do away with intracardiac valves for prevention of regurgitation. There is less wear and tear as the fins float within the centrifugal pump due to magnetic levitation technology. The device was developed In. Queensland, Australia and FDA-approved clinical trial at the Texas Heart Institute. The first clinical trial was satisfactory.
Implantable in terminally ill heart failure patients artificial devices that can maintain the circulatory demands of the human body are still the "holy grail''. The ideal prosthetic heart should be able to steadily maintain the perfusion with O² demands of tissue, and sustain a meaningful existence during the period of life, and the time-induced wear should be minimal. It needs little mention that a total cardiectomy involves all remnant unrecoverable contractile cardiac muscle. The implant has to work on its own and maintain viable circulation. Stringent trials are needed as the human life of a subject depends on the device.
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