Cardiovascular System MCAT Practice Question
A 35-year-old man with a known ventricular septal defect presents to clinic for routine follow-up. He reports progressive dyspnea on exertion over the past 2 years. Physical examination reveals a systolic murmur at the left lower sternal border, and a prominent P2 component of the second heart sound. Chest X-ray shows cardiomegaly with pulmonary vascular congestion. Echocardiography confirms a moderate left-to-right shunt with a Qp:Qs ratio of 2.5:1. Laboratory studies show a normal hemoglobin and hematocrit. Which of the following pathophysiologic changes in the pulmonary vasculature is most consistent with the development of pulmonary hypertension in this patient?
Answer choices
- AEndothelial dysfunction leading to increased nitric oxide production and vasodilation
- BMedial hypertrophy and smooth muscle proliferation of pulmonary arterioles with intimal fibrosisCorrect answer
- CPulmonary arterial dilation with thinning of the vessel wall to increase capacitance
- DSelective loss of distal pulmonary arterioles reducing total vascular bed
- EDecreased pulmonary vascular tone secondary to chronic hypoxemia compensation
- FBronchial arterial hypertrophy with systemic-to-pulmonary collateral formation
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