A Wiggers diagram shows that left ventricular pressure exceeds aortic pressure during a brief interval of the cardiac cycle. This crossover represents which event?

• A Transition from isovolumetric contraction to ejection phase ✓
• B Aortic valve closure at the beginning of isovolumetric relaxation
• C Mitral valve opening at end of rapid ventricular filling
• D Atrial kick contributing to final ventricular filling

Explanation

During isovolumetric contraction, LV pressure rises while the aortic valve remains closed. The moment LV pressure first exceeds aortic diastolic pressure, the aortic valve opens and ejection begins—this is the LV-aorta pressure crossover. A second crossover occurs when LV pressure falls below aortic pressure, marking valve closure and onset of isovolumetric relaxation.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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