© 1962 American Heart Association, Inc.
Dynamics of Ventricular Ejection
1 Department of Physiology and Pharmacology and the Department of Obstetrics and Gynecology, Bowman Gray School of Medicine of Wake Forest College Winston-Salem, North Carolina
Left ventricular ejection in open-chest, anesthetized dogs begins with an abrupt acceleration of blood into the ascending aorta, reaching an average maximum of 4,650 cm./sec./sec. Velocity reaches a sharp peak of 88 cm./sec. (average) within the first one-third to one-half of the ejection period. Deceleration is more gradual and continues to the closure of the aortic valve. The general pattern of the time-course recording is that of a triangle with its peak skewed into early systole and separated from a flat diastolic period of zero flow by a deep notch of backflow attending closure of the aortic valve. Ventricular pressure exceeds aortic pressure only during the brief period between the opening of the valve and peak systolic velocity, a period of approximately 45 per cent of the ejection period. This "positive" (headward) gradient represents the acceleration transient and explains the sharp rise in flow to a maximum in early systole. During the deceleration (terminal) phase of ventricular ejection, the pressure gradient is against the direction of flow. This reversal in pressure gradient brings about a gradual deceleration of flow to zero. These findings are considered experimental proof that the major phenomenon relating pressure and flow in the ascending aorta is that governing mass acceleration.
Submitted on August 21, 1961
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