Is a totally implantable artificial heart realistic?
The incidence of local infection that occurred after the implantation of the intrathoracic Jarvik 7 total artificial heart (J-7 TAH) in patients was a major problem of this cardiac prosthesis. Infection rates increased when the J-7 TAH was implanted for longer periods of time, which was contrary to the results that were obtained by the implantation of the left ventricular assist devices (LVAD) either in the abdominal cavity or in the abdominal wall. Currently, the general belief is that the implantation of a cardiac prosthesis inside of the chest cavity is not safe, due to higher rates of infection. Thus, Part I of this paper deals with the question: "Is a total artificial heart physiologically acceptable?" We believe structural differences of the J-7 TAHs and other LVADs are an important part of the problem. The J-7 TAH is a volumetrically dynamic pump, and the other LVADs are a volumetrically fixed stationary pump. Based upon experiences of this investigator, intrathoracic implantation of a smooth surface pulsating device (or a volumetrically dynamic pump) generated persistent local inflammatory reactive tissues directly adjacent to the device. These tissue capsules were nonadherent to the device, and therefore may produce an ideal environment for allowing bacteria to grow. The findings were opposite to those for a non-pulsating surface pump inside the chest cavity. Part II of this paper discusses the question: "Is a totally implantable artificial heart technically achievable?" Many technical problems for the totally implantable TAH were already resolved during the development program of the totally implantable LVAD. However, there are three TAH specific problems that remain to be solved before achieving a clinically useful totally implantable TAH system. They are (a) anatomical compatibilities of the TAH system; (b) reliable control of the TAH system, (c) reliable and effective long-term operation of the TAH system. We have resolved the anatomical problem by the integral design of the pump-actuator system. Overall size of the hard shell Baylor TAH system is 510 cm3 with a diameter of 97 mm and a width of 82 mm. Its stoke volume was reduced to 63 cm3. The stable and reliable control of TAH performances was established by the three sets of Hall effect sensors with left master alternate mode of pumping. No physiological parameter was used as a feedback signal. Reliable long-term operation of the TAH system was established by the electromechanical actuation system. A simple drive mechanism with commercially available components and subsystems was used.(ABSTRACT TRUNCATED AT 400 WORDS)
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Department of Surgery, Baylor College of Medicine, Houston, Texas 77030.
D000818:Animals; D001672:Biocompatible Materials; D002417:Cattle; D006354:Heart, Artificial / Q000009:adverse effects; D006801:Humans; D007111:Immunity, Cellular; D011183:Postoperative Complications; D011474:Prosthesis Design; D016459:Prosthesis-Related Infections / Q000503:physiopathology
D001672:Biocompatible Materials