An 80-year-old man has a blood pressure of 168/62 mmHg. Cardiac output and peripheral resistance measured in the laboratory are within normal limits. The primary abnormality explaining his wide pulse pressure is:
- A Increased capacitance of the muscular arteries
- B Reduced compliance of the aorta and large elastic arteries ✓
- C Excessive beta-adrenergic stimulation of the heart
- D Decreased systolic ejection velocity from the left ventricle
Correct answer: B. Reduced compliance of the aorta and large elastic arteries
Explanation
With aging, elastin fragmentation and collagen deposition stiffen the proximal aorta. During systole the aorta cannot expand normally, so systolic pressure rises sharply; during diastole there is less elastic recoil to sustain diastolic pressure, so it falls. The result is isolated systolic hypertension with a widened pulse pressure despite normal cardiac output and resistance. Increased capacitance in option A would narrow, not widen, the pulse pressure.
Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.
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