A 25-year-old man with infective endocarditis has a collapsing 'water-hammer' pulse with a wide pulse pressure of 110/40 mmHg. The combination of a high systolic pressure and low diastolic pressure in aortic regurgitation is explained by:
- A Increased stroke volume ejected into a compliant aorta plus diastolic runoff back into the left ventricle ✓
- B Decreased aortic compliance raising systolic pressure while regurgitation lowers diastolic pressure
- C Reflex sympathetic activation constricting arterioles and elevating both pressures
- D Reduced effective circulating volume stimulating renin release and volume retention
Correct answer: A. Increased stroke volume ejected into a compliant aorta plus diastolic runoff back into the left ventricle
Explanation
In chronic aortic regurgitation, the left ventricle undergoes eccentric hypertrophy and ejects a greatly enlarged total stroke volume, which raises systolic pressure. During diastole, blood flows backward into the ventricle and forward into the periphery, so diastolic pressure falls rapidly. The result is a wide pulse pressure with bounding pulses. Aortic compliance is actually increased in chronic regurgitation, which rules out option B.
Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.
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