During what phase does the dicrotic notch occur?

The dicrotic notch occurs after the closure of the aortic valve, which marks the transition from systole to diastole in the cardiac cycle. This notch is a small downstroke seen in the arterial pressure waveform that reflects the brief period of backflow of blood as the aortic valve closes. When the left ventricle finishes contracting and the aortic valve closes, a sudden rise in pressure can occur momentarily due to the elasticity of the aorta and the rebound of pressure against the recently closed valve, causing this distinctive notch.

This notch is an important feature because it provides insight into the hemodynamic status of the heart and the aorta. It signifies the moment when the heart begins to relax and blood flow to the peripheral circulation proceeds under a lower pressure. Understanding this timing helps in assessing cardiovascular health and function, making it crucial in interpreting cardiac pressures and dynamics. The other phases listed do not relate directly to the dicrotic notch occurring in the pressure tracing.