Experimental Studies in Total Artificial Heart Replacement : SYMPOSIUM ON ARTIFICIAL CONTROL OF CIRCULATION : EXPERIMENTAL RESULTS AND CLINICAL APPLICATIONS

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Twenty-seven calves were operated on in our institute for total artificial heart replacement. Thomasu hearts (made by the Thomasu Technical Company, Japan) were used in 21 calves from February 1980 to May 1983. Utah Jarvik 7 hearts were used for the first five calves and the 17th calf. The air-driven Thomasu heart, made of segmented polyurethane, has 95 ml and 85 ml of stroke volume in its left and right sides respectively and showed recognizable function curves in mock circulation systems. There were no satisfactory results in the first 19 cases but the 20th calf survived for 28 days. In 1982, we adopted a new surgical method in which, instead of suturing, a sutureless artificial graft with a stainless steel ring was inserted into the aorta and pulmonary truncus. Since then two out of six calves have survived for more than one month; one of these survived for 66 days. The causes of death after the Thomasu heart replacements were varied. Ten (48%) out of 21 cases had heart trouble and four calves (19%) died through thrombus formation at the inflow and outflow valves. Three calves (14%) died because of mechanical failure of the driving system, two (10%) due to surgical failure, one because of pneumonia, and one due to an abnormal reaction after donor blood transfusion. Our longest surviving calf died after 66 days, because of a broken left blood diaphram though, it remained in excellent condition until its death. There was no thrombus formation in either ventricle, no fibrin net formation and no calcium deposit on the surface of the diaphragm. The surgical technique and establishment of extracorporeal circulation in total artificial heart replacement have been confirmed as successful, especially when a sutureless technique is adopted for the outflow tract, but problems remain with the manufacture and durability of the heart. The resolution of these difficulties lies in the field of engineering science, but with development in this area we can certainly look forward to six-month survival in the calf.