Starling's law of the heart. VII: Ventricular function in closed-chest unanesthetized dogs

It is generally agreed that Starling's law applies to heart-lung preparations and open-chest, anesthetized dogs. However, there is considerable disagreement about the relevance of the Frank-Starling mechanism to the intact organism. A Kolin-Kado gated, sine wave, electromagnetic flowmeter was placed around the ascending aorta of seven dogs. Changes in left ventricular dimensions were recorded with mercury resistance gauges. Left ventricular diastolic and intrapleural pressures were measured simultaneously. The chest was closed and the dogs permitted to recover from the anesthesia and to breathe spontaneously. Alterations in left ventricular size and effective filling pressure were induced by rapid transfusion or bleeding. Left ventricular stroke work, peak values of aortic blood velocity and acceleration, and left ventricular power all increased as left ventricular size and filling pressures were augmented. At any given filling pressure and ventricular size all these indices of ventricular performance increased during infusion of norepinephrine. These experiments support the view that Starling's law and the ventricular function curve concept are applicable to the heart of the closed-chest, unanesthetized dog with an intact autonomic nervous system.