Cardiac Cycle - Rapid Ejection (Phase 3)

Aortic and Pulmonic Valves Open; AV Valves Remain Closed

This phase represents the initial and rapid ejection of blood into the aorta and pulmonary arteries from the left and right ventricles, respectively. Ejection begins when the intraventricular pressures exceed the pressures within the aorta and pulmonary artery, which causes the aortic and pulmonic valves to open. Blood is ejected because the total energy of the blood within the ventricle exceeds the total energy of blood within the aorta. In other words, there is an energy gradient to propel blood into the aorta and pulmonary artery from their respective ventricles. During this phase, ventricular pressure normally exceeds outflow tract pressure by a few mmHg. This pressure gradient across the valve is ordinarily low because of the relatively large valve opening (i.e., low resistance). Maximal outflow velocity is reached early in the ejection phase, and maximal (systolic) aortic and pulmonary artery pressures are achieved.

No heart sounds are ordinarily noted during ejection because the opening of healthy valves is silent. The presence of sounds during ejection (i.e., ejection murmurs) indicate valve disease or intracardiac shunts.
Left atrial pressure initially decreases as the atrial base is pulled downward, expanding the atrial chamber. Blood continues to flow into the atria from their respective venous inflow tracts and the atrial pressures begin to rise, and continue to rise until the AV valves open at the end of phase 5.

Jump to other phases:

Revised 04/13/07