This paper reviews the current status of completely implantable cardiac prostheses, with an emphasis on those systems presently under development at the Cleveland Clinic Foundation (CCF). Such devices have been one of the final goals of artificial heart research since 1957, when Dr. Kolff initiated these studies in Cleveland. Although earlier plans aimed at using radioisotopes as the energy source, more recently, due to public opinion and sociopolitical influences, the shift has been towards exclusive use of electrically activated energy converters. These systems can be roughly broken down into two groups according to the powertrain configuration. In the first group, electric heating coils maintain liquid salts in thermal batteries at temperatures close to 500°C. This thermal energy is then converted (through a Stirling cycle) to mechanical motion of the pusher plate (PP) which in turn acts on the blood. Two such systems (emphasized in this paper) are under development here at CCF in joint efforts with Nimbus Corp. and the University of Washington, respectively. In the second group of VAS's, electric energy is converted directly to PP motion through rotating cams, solenoids, or electrohydraulic transmission systems. At least four American contractors are working at the pre-clinical stage on this group of devices. One in particular, the CCF-Nimbus system, consisting of a biolized surface blood pump, an electrohydraulic energy converter, and a compliance chamber to handle the variable volume behind the PP, is described in depth in this discussion.
In terms of future prospects, it is forecasted that by 1988, the completely implantable VAS will be used clinically, and that by 1994, a specially designed total artificial heart (non-tethered patient) would be ready for human use.

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A new polyglycolic acid absorbable surgical suture, MEDIFIT, was studied on the physical, chemical and biological properties and the clinical evaluation. The knot tensile strength of MEDIFIT is very tough. According to in vitro and in vivo studies, the retention of the tensile strength of MFDIFIT was nearly equivalent to DEXON's and VICRYL's. Percent values of the retention after 14 days immersion were 75.2% in the saline, 82.2% in the gastric juice, 66.8% in the bile and 66.2% in the pancreatic juice, respectively. Decrease in the tensile strength of implanted sutures subcutaneously to rabbits was similar to the immersed sutures in the bile. MEDIFIT implanted intramuscularly to rabbits has been absorbed completely within 15 weeks after implantation as well as DEXON. The tissue reactivities were extremely slight, and filaments of the suture have been replaced by the connective tissue during the absorption process. The safety and the handling character of MEDIFIT were satisfied on clinical applications. Conclusively, MEDIFIT can be useful and valuable as a new absorbable surgical suture.

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The effectiveness of a hybrid artificial liver consisting of isolated hepatocyte suspension and semipermeable membrane has been established by our group. We searched for effective factors which may be released from the hepatocytes and supplied through the membrane to the blood of model animals. Hepatocytes obtained from rabbits were cultivated in a suspension for 12hr and the supernatant was concentrated by ten times. The concentrate was administered twice intraperitoneally to rats poisoned with Dgalactosamine in advance. Survival rate of the rats was significantly higher than that of the control rats which were treated with the corresponding amount of concentrate of fresh culture medium. The result suggests the presence of effective factors in the supernatant of cultivated hepatocytes.

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Some ill effects were suspected after the use of a high concentration of oxygen in the artificial lung during long term extracorporeal lung assist (ECLA, a new acronym coincides with ECMO: extracorporeal membrane oxygenation). Six out of nine goats were subjected to ECLA with 100% oxygen and the other 3 goats with 30% oxygen. The survival rate, length of extracorporeal circulation, general conditions and platelet counts were studied. In the 100% oxygen group, 5 out of 6 goats died on the 6th day of ECLA and only one goat survived after 7 days of ECLA. The platelet counts usually remained at a low level (below 50%) compared to the pre-level of ECLA. In the 30% oxygen group, all three goats survived after 18, 23 and 38 days of ECLA, and their general conditions were well maintained. The platelet counts in this group initially dropped, but returned to 50% or more of the pre-level of ECLA from the 3rd day on. Small bubbles, which might be caused by supersaturation mechanisms, were found in the blood phase of the artificial lung during the use of 100% oxygen. A high concentration of oxygen in the artificial lung caused microbubbles, and could lead to platelet reduction as well as organ damage through oxygen toxicity. These results suggest the necessity of using a low concentration of oxygen in the artificial lung as far as possible.

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In patients implanted with a pacemaker, radiotherapy may be chosen as the treatment when malignant tumor is complicated. Therefore, on the assumption that the pacemaker apparatus is exposed to X-ray, 21 lithium cells used for CMOS or TTL circuit were collected before expiration date and irradiated with ⁶⁰Co. The pacemaker used were 10 apparatuses of unprogrammed model VVI, 9 apparatuses of programmed model VVI and 2 apparatuses programmed model DVI. Irradiation was done up to 1, 000 rads in dividing doses or at 1, 000 rads as a single dose. Observations were made for effects on intervals, amplitude and wave shape of stimula to pacemaker, power, sensitivity, refractory phase, and program functions. In conclusion, it was found that pacemaker is sure to be affected considerably for various functions, although no functional arrest occurs, under irradiation up to 1, 000 rads of ⁶⁰Co in dividing dose. When irradiation at 1, 000 rads was given as a single dose, dysfunctions of pacemaker developed in some cases indicating that direct irradiation at high doses is contraindicated for pacemakers using much of LSI-CMOS.

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In general there are fewer symptoms of hypotension and disequilibrium syndrome during hemofiltration (HF) than during hemodialysis (HD). We compared influence on cardiac function of HD with that of HF by crossover study in seventeen patients with chronic renal failure. Hematocrit, blood chemistry, serum electrolytes and cardiothoracic ratio revealed no significant differences before HD and before HF in each case. Method: Cardiac function was measured using a Swan-Ganz catheter, and measurements were taken prior to, every hour after starting, and after ending the procedures. Results: 1) The reductions in %SWI (rate of variation of left ventricular stroke work index) associated with the changes of ΔPCWP (variation of pulmonary capillary wedge pressure) intended to be smaller during HF than during HD. 2) The reductions in %SWI associated with the increase of %ΔBW (rate of reduction of body weight) were significantly (p<0.005) smaller during HF than during HD, and the relations between %SWI and %d BW indicated high inverse correlation coefficients for both HD and HF. Conclusion: Our findings suggested that in terms of left ventricular contractility HF had less influence on cardiac function than did HD.

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