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Cardiac Cycle - Rapid Ejection (Phase
3)
Aortic and Pulmonic Valves Open; AV
Valves Remain Closed
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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.
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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.
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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:
Phase 1 - Atrial Contraction
Phase 2 - Isovolumetric Contraction
Phase 4 - Reduced Ejection
Phase 5 - Isovolumetric Relaxation
Phase 6 - Rapid Filling
Phase 7 - Reduced Filling
RK Revised
04/13/07
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Cardiovascular Physiology Concepts
