The arterial pulse is produced by the ejection of blood into the aorta. The normal configuration of the pulse consists of a smooth and rapid upstroke that begins about 80 msec after the first component of S1. There is sometimes a slight notch in the arterial pulsation toward the end of the rapid ejection period. This is called the anacrotic notch. The peak of the pulse is smooth and dome-shaped and occurs about 100 msec after the onset of the pulse. The descent from the peak is less steep. There is a gradual descent to the dicrotic notch, which represents the closure of the aortic valve. The contour and volume of the arterial pulse are determined by several factors, including the left ventricular stroke volume, the ejection velocity, the relative
--Figure 14-8 The arterial pulse.
Figure 14-7 Physiologic splitting of the second heart sound.
compliance and capacity of the arteries, and the pressure waves that result from the antegrade flow of blood. Figure 14-8 illustrates a characteristic arterial pulse.
As the arterial pulse travels to the periphery, there are several changes. The initial upstroke becomes steeper, the systolic peak is higher, and the anacrotic notch becomes less evident. In addition, the dicrotic notch occurs later in the peripheral pulse, approximately 300 msec after the onset of the pulse. The positive wave that follows the dicrotic notch is called the dicrotic wave.
Commonly, two waves may be present in the arterial pulse, which precedes the dicrotic notch. The percussion wave is the earlier wave and is associated with the rate of flow in the artery. The percussion wave occurs during peak velocity of flow. The tidal wave is the second wave, is related to pressure in the vessel, and occurs during peak systolic pressure. The tidal wave is usually smaller than the percussion wave, but it may be increased in hypertensive or elderly patients.
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