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Diagram of events in the cardiac cycle. From top downward: pressure (in millimeters of mercury) in aorta, left ventricle, left atrium, pulmonary artery, right
ventricle, right atrium; blood flow (mL/s) in ascending aorta and pulmonary artery; ECG. Abscissa, time in seconds. (Valvular opening and closing are
indicated by AO and AC, respectively, for the aortic valve; MO and MC for the mitral valve; PO and PC for the pulmonary valve; TO and TC for the
tricuspid valve.) Events of the cardiac cycle at a heart rate of 75 bpm. The phases of the cardiac cycle identified by the numbers at the bottom are as
follows: 1, atrial systole; 2, isovolumetric ventricular contraction; 3, ventricular ejection; 4, isovolumetric ventricular relaxation; 5, ventricular filling. Note that
late in systole aortic pressure actually exceeds left ventricular pressure. However, the momentum of the blood keeps it flowing out of the ventricle for a
Source: Cardiovascular Disorders: Heart Disease, Pathophysiology of Disease: An Introduction to Clinical Medicine, 7e
short period. The pressure relationships in the right ventricle and pulmonary artery are similar. (Redrawn, with permission, from Milnor WR. The
Citation:
Hammer
McPheePhysiology,
SJ. Pathophysiology
of Disease:
circulation. In:
Mountcastle
VB,GD,
ed. Medical
2 vols. Mosby,
1980.) An Introduction to Clinical Medicine, 7e; 2013 Available at:
http://mhmedical.com/ Accessed: May 07, 2017
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