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Seven calves underwent thoracotomy to study the response of 41 physiologic variables over a 14 day post-operative period for comparison to a recent series of left ventricular bypass pump implants. The experimental protocols were identical to the pump implant protocols except that the sham operated animals did not receive antiplatelet or anticoagulant drugs and the pumps were not implanted. Of the 41 variables studied, 13 changed significantly during the post-operative period. Heart rate, hematocrit, whole blood hemoglobin, and fibrinogen concentration decreased, while fibrinogen survival, stroke volume, cardiac output, arterial blood pH, pCO2 and pO2, plasma sodium concentration, and urinary excretion rates of sodium and potassium increased from the first or second to the fourteenth post-operative day. Heart rate and hematocrit also decreased in the recent series of 18 animals in which left ventricular bypass pumps were implanted. The decrease in heart rate is toward the unoperated control value as the calves recover from the operative stress. The decrease in hematocrit is probably the result of daily removal of blood for the physiologic studies because there was no evidence of hemorrhage or red blood cell destruction.

A stable model of left ventricular failure is required to test left ventricular assist devices. Supravalvular aortic constriction will cause left atrial pressure to rise to new levels which are stable for several days. When left atrial pressure becomes unstable, an automatically actuated left ventricular assist device will increase its output and prevent pulmonary edema.

The current Baylor left ventricular bypass pump is a pneumatically actuated diaphragm pump lined with segmented polyurethane. It is a swirl design in which blood moves in a circular motion within the pump. It has tilting disc inflow and outflow valves and the stroke volume is 60 ml. It is intended for periods of use up to fourteen days. Eighteen devices have been implanted in normal calves. The mean duration of pump operation was eleven days. The pump-canula junctions and regions of the valve seats have been sites of thrombus formation and are being redesigned to eliminate areas of flow separation and stasis.

<$O_ST_ABS>AUTHORS SYNOPSIS<$C_ST_ABS>Experimental coronary artery disease (CAD) was produced in dogs which had chronically implanted catheters for the measurement of mean arterial pressure (MAP) and coronary blood flow (CBF) using the 85Kr clearance technique. Resting CBF was determined in the conscious animal during intracoronary infusion of saline and the maximum CBF was determined by infusion of ATP (0s·6 and 0·8 mg/min). Repeated observations revealed only small and variable changes in MAP and CBF of control dogs over a two-month period and of dogs fed an atherogenic diet containing thiouracil and cholesterol for 47 and 54 days. CAD was produced by intracoronary infusion of allylamine and intravenous infusion of egg yolk emulsion. This treatment results in arteritis, lipid deposition, and fibrosis. The disease was associated with a 37% decrease in maximum CBF within two to five days. Resting CBF decreased 16% and MAP was not altered significantly. After the initial decrease in maximum CBF, there is a stable period with decreased maximum CBF for at least six weeks.