Landis Dl

Complete Left Ventricular Bypass With a Paracorporeal Pump: Design and Evaluation

A multidiscipline group was established at The Pennsylvania State University to design and evaluate mechanical circulatory assist devices and the artificial heart. The group has designed a left ventricular to aortic assist system which consists of a sac-type pump, a synchronization unit, a pneumatic power unit, and appropriate monitoring apparatus. The assist system has been evaluated for long-term circulatory assistance in a series of ten calves. The assist pump was placed in the paracorporeal position. The longest period of continuous pumping was over eight months. The last four calves have had synchronized assist pumping which has permitted prolonged ventricular decompression and assist pump flow rates as high as 10 L/min. Three of these four calves had no evidence of thromboemboli. Additional animal studies will be required before clinical use of such an assist pump system can be safely undertaken.

Total artificial heart implantation in calves with pump on an angled port design.

The APP was employed in our 21st TAH calf and has now been implanted in a total of 11 animals. The APP has a dynamic stroke volume of 105 ml, an ejection fraction of 75%, and a peak flow of 14 L/min. The TAH features 2 APPs which have polysulfone cases and contain smooth, seam-free polyurethane sacs. Concavoconvex Bjork-Shiley valves are used. The pumps are pneumatically driven but may be easily converted to pusher-plate drive. A pneumatic drive console and an automatic control unit complete the system. The automatic control unit permits independent control of the right and left hearts as a function of left atrial and aortic pressure respectively. The average survival of the APP TAH calves has been 65 days. Hematologic study has revealed basically normal results with minimal elevation of serum hemoglobin and lactic acid dehydrogenase (LDH), indicative of a low level of hemolysis. Elelvation of central venous pressure (CVP) and total blood volume continue to be a problem with some TAH calves but not all. The APP has led to a dramatic increase in duration of survival and decrease in thromboembolism.