Applications of total artificial heart for studies of circulatory physiology; measurement of resistance to venous return in postoperative awake calves. Preliminary report.

Abstract

The objectives of total artificial heart (TAH) research are twofold: (1) clinical use for total replacement of an irreversibly diseased heart; and (2) experimental use for studies in basic medical science, especially in the field of circulatory physiology. This paper is related to the second objective and one of the preliminary reports on experiments along this line. The results demonstrate the possibility of determining the venous return curve (VRC) and the resistance to venous return (RVR) in completely awake calves with an orthotopically implanted TAH. Our air-driven TAH was made of silicone rubber. Calves used weighed from 80 to 90 kg. Studies were performed following their recovery from the implantation surgery. The process of RVR determination was as follows: (1) The original equilibrium point (A) of the cardiac output (CO) and VR was determined, (2) the second equilibrium point (B) with a reduced CO was determined, (3) the VRC was constructed from points A and B which should be on the same VRC, (4) the momentary mean systemic pressure (MSP) was obtained at the point of interception of the VRC and abscissa (right atrial pressure (RAP)), and (5) thus, RVR was calculated from the equation (MSP—RAP)/CO. Calculated RVR ranged from 0.09 to 0.28 mm Hg/ml/sec under the conditions of these experiments.