A patient with severe aortic regurgitation has a widened pulse pressure and a low diastolic blood pressure. The primary mechanism causing the reduction in diastolic blood pressure is:

• A Reduced stroke volume due to ventricular failure
• B Increased baroreceptor-mediated vasodilation reducing peripheral resistance
• C Regurgitant flow back into the left ventricle causing rapid arterial pressure decay ✓
• D Decreased venous return reducing preload

Explanation

In aortic regurgitation, the incompetent aortic valve allows blood to flow backward from the aorta into the left ventricle during diastole. This regurgitant flow rapidly empties the aorta, causing the characteristic low diastolic pressure and widened pulse pressure. The stroke volume is actually increased (due to Frank-Starling compensation from volume overload), raising systolic pressure further and exaggerating the pulse pressure. This mechanism explains signs like Corrigan's pulse and pistol shot sounds.

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

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