During diastole, when the heart relaxes, pressure declines back to 80 mm of mercury. The small secondary pressure increase in the beginning of diastole is referred to as the 'dicrotic notch' and is due to closure of the aortic valve and elastic recoil of the aortic wall.

What is the Dicrotic notch and when does it occur?

Introduction The dicrotic notch is a small and brief increase in arterial blood pressure that appears when the aortic valve closes.

During which phase of the cardiac cycle does the Dicrotic notch occur?

Ventricular Diastole

When pressure within the ventricles drops below pressure in both the pulmonary trunk and aorta, blood flows back toward the heart, producing the dicrotic notch (small dip) seen in blood pressure tracings. The semilunar valves close to prevent backflow into the heart.