Page 24, Blood Pressure, Dr. D. Penney

Pulse Pressure (continued...)

For the normal pulse wave, the systolic pressure is 140 mmHg and the diastolic pressure is 75 mmHg (Figure 13). With aortic stenosis, the top of the pulse wave is flattened. This results from the greatly increased outflow resistance. While blood is still being ejected into the aorta, the rate of ejection is limited. Thus, systolic blood pressure is decreased, decreasing pulse pressure.

With atherosclerosis, there is a decrease in compliance of the arterial wall (Figure 13). Pressure during ejection rises steeply, since the pressure energy is not being taken up by wall stretch. When the ventricle stops contracting and the valve closes the pressure drops sharply because there is little stored energy of elastic recoil. This creates a very large pulse pressure.

With aortic insufficiency (or incompetence, regurgitation) the pressure in the aorta rises sharply during ejection, but falls equally sharply when the valve closes (Figure 13). This is because blood is running-off not only to the arterial tree, but also back into the ventricle. There is usually a compensatory increase in the force of ventricular contraction in aortic insufficiency. Aortic insufficiency is characterized by very low diastolic pressure, whereas in arteriosclerosis a high pulse pressure is accompanied by a more or less normal diastolic pressure.

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