EVOLUTION OF AN ELECTROHYDRAULIC VENTRICULAR ASSIST DEVICE THROUGH IN-VIVO TESTING

A totally implantable intrathoracic electrohydraulic ventricular assis t device has been developed at the University of Ottawa Heart Institut e. In vivo testing has been instrumental in its progressive developmen t. A total of 15 experiments (4 acute, 11 performance) have been perfo rmed using male calves (62-117 kg). Data from the acute experiments, h uman fit trials, fluid dynamic studies, and hydraulic/energy efficienc y analyses formed the basis for the development of a compact, single p iece ventricular assist device called the Unified System in which the volume displacement chamber, motor, and blood chamber are housed withi n a compact 600 cc, 740 g unit. The performance experiments indicated that the unified system could support calves for periods up to 96 hr. The mean postoperative cardiac output was 7.1 +/- 0.7 L/min (range = 4 .9-11), mean blood pressure was 99.7 +/- 5.8 mmHg, and mean pulmonary artery pressure was 32.1 +/- 1.2 mmHg. The operative technique for int rathoracic implantation has been developed. The major problems encount ered were of respiratory failure, improved by device repositioning in the calf; decreased blood inflow to the device that was improved by ca nnula redesign; circuit board fracture corrected by design modificatio n; and a power supply problem that was limited to a single unit. The p reliminary experiments have helped in the design modifications of the Unified System. The improved version of the system will undergo formal performance, reliability, and chronic in vivo testing before human im plantation.