A catheter in the ascending aorta records a sharp incisura (dicrotic notch) followed by a brief pressure rise before diastolic decay. This notch coincides with which event?
- A Opening of the aortic valve
- B Peak left ventricular ejection
- C Closure of the aortic valve ✓
- D Closure of the mitral valve
Correct answer: C. Closure of the aortic valve
Explanation
As left ventricular pressure falls below aortic pressure at the end of ejection, the aortic valve closes. Elastic recoil of the aorta briefly reverses flow toward the valve, producing the incisura, which occurs simultaneously with the second heart sound. Aortic valve opening instead produces the anacrotic limb of the upstroke, and mitral closure marks the start of isovolumetric contraction with no visible notch on the aortic trace.
Reference: Ganong's Review of Medical Physiology, 26th ed.
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