Adaptation of the organism during long-lasting survival with a total artificial heart.

Abstract

The present chapter is a report of the current status of our testing of total artificial heart (TAH) implants in over 50 calves. Our 50th TAH experiment was performed with the calf Hasan; the experiment lasted 150 days. The TAH used in this experiment was TNS-BRNO-II, made of polymethylmethacrylate with polyurethane diaphragm and valves. Basic physiological functions normalized very soon after surgery. Blood flow through the device gradually increased from 7.5 to 11.5–12.5 liter/min at the end of the experiment. Central venous pressure (CVP) increased to 2.0–2.5 kPa in later months; atrial pressures were automatically maintained at the same level, ca. 1 kPa on both sides during the whole experiment. Anticoagulant therapy kept the prothrombin time two- to threefold above normal. The experiment was terminated by a sudden impairment of the blood coagulation mechanism, marked GI bleeding, and acute cerebral anemic anoxia. Autopsy revealed no thrombi at the artificial valves; there was thick pseudo-neointima in the outer portion of the diaphragm; inlet orifices were clean, without traces of pannus on either side. There were no signs of infection of organs detectable by the autopsy, but bacteriological examination revealed Klebsiella infection. Another experiment with the TAH, no. 51, was started immediately after experiment no. 50 was terminated. The calf, named Dalibor, recovered very quickly from surgery and anesthesia; about 3 weeks after surgery, basic physiological functions were stabilized , and during the subsequent course there were no problems in postoperative care. The calf was anticoagulated with warfarin (Coumadin®) until the 102nd day when slight GI bleeding occurred, and the administration of warfarin was interrupted. Only antiaggregation therapy with dipyridamole (Curantyl®) and aspirin was used from that time. Dalibor survived for 142 days in full health and died of accidental causes. During the calf s survival period, its CVP oscillated between 3 and 2.8 kPa, and blood flow through the TAH averaged 13 liter/min. The technical equipment used in both these experiments functioned without the slightest disturbance. In both experiments, the internal milieu of the calves showed absolute adaptation and normalization of all basic parameters, especially in the second calf, Dalibor. A third calf, no. 52, Samson, of this group survived 104 days; the cause of death was diaphragm leakage in the right-hand pump. The longest survival to date was achieved in calf no. 53, Florian, which survived 155 days; the cause of death was microthrombembolization in the CNS. The last calf of this group, no. 54, Waldemar, survived 31 days; the experiment was terminated because of a thrombembolism into the superior mesenteric artery. The mean survival of our five calves that lived longer than 1 month was 116 days. During their survival time, the basic physiological functions of all of these animals were fully normalized; the calves gained weight, and their condition was very good. These facts have documented excellent adaptation of these animals to the TAH. The control and driving unit used in our experiments with the TAH is an apparatus produced in our institute and designated Chirasist TN 3.