Quantitative Effect of Low Coronary Pressure on Left Ventricular Performance

Ventricular output curves (left ventricular output vs. left atrial pressure) were studied with coronary arterial pressure controlled at various subphysiological levels in anesthetized dogs. The coronary pressure was changed with a small screw clamp placed around the left main coronary artery, in which a tiny catheter was introduced for coronary pressure measurement. The aortic pressure and cardiac output were controlled at constant values independent of coronary pressure. At low coronary pressures, depression of the plateau and rightward shift of the ventricular output curves was observed. The effect was more marked as the set coronary pressure was lowered. It was concluded that the change in maximal cardiac output (plateau level of the output curve) is a sensitive index of the integrity of cardiac function and that reduction in coronary pressure during hypotensive states plays an important role in the development of vicious cycle of cardiac deterioration. Also observed in the experiment was a consistent correlation between electrocardiographic changes and alterations in cardiac function.