Heart Model
Cardiovascular Physiology Concepts Richard E. Klabunde, PhD

Cardiovascular Physiology Concepts 3e textbook cover Cardiovascular Physiology Concepts, 3rd edition textbook, Published by Wolters Kluwer (2021)

CNormal and Abnormal Blood Pressure, Physiology, Pathophysiology and Treatment book cover Normal and Abnormal Blood Pressure, published by Richard E. Klabunde (2013)

Aortic and Arterial Pulse Pressure

As the left ventricle ejects blood into the aorta, the aortic pressure increases to its peak systolic value. The greater the stroke volume, the greater the change in aortic pressure during ejection. The maximal change in aortic pressure during systole, from the time the aortic valve opens until the peak aortic pressure is attained (see Cardiac Cycle), represents the aortic pulse pressure, which is defined as the systolic pressure minus the diastolic pressure. For example, if the systolic pressure is 130 mmHg and the diastolic pressure is 85 mmHg, then the pulse pressure is 45 mmHg.

Pulse Pressure = Systolic Pressure − Diastolic Pressure

Aortic expansion and contractionThe rise in aortic pressure from its diastolic to systolic value is determined by the ventricular stroke volume and the compliance of the aorta. In the arterial system, the aorta has the highest compliance, due in part to a relatively greater proportion of elastin fibers versus smooth muscle and collagen. This serves the important function of dampening the pulsatile output of the left ventricle, reducing the pulse pressure (systolic minus diastolic arterial pressure). If the aorta were a rigid tube, the pulse pressure would be very high. Because the aorta is compliant, as the ventricle contracts and ejects blood into the aorta (red arrows on the left side of the figure), the walls of the aorta passively expand to accommodate the increase in blood volume. As the aorta expands in volume, the increase in pressure is determined by the compliance of the aorta for that range of volume change. As the blood leaves the aorta and the pressure falls, the walls of the aorta passively contract (recoil) until the next cardiac ejection (right side of the figure). At a given stroke volume, a less compliant (stiffer) aorta will have a greater pulse pressure because the systolic pressure will be higher and diastolic pressure will be lower (assuming unchanged systemic vascular resistance) because of greater elastic recoil during diastole. Therefore, aortic compliance and stroke volume are a major determinant of pulse pressure.


Revised 11/03/2023



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