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Difficulty: EasyCardiovascular System

During a routine outpatient evaluation, a physician examines a patient with a long-standing history of severe chronic obstructive pulmonary disease. The patient reports a three-month history of progressive bilateral leg swelling and a noticeable decline in exercise tolerance. Vital signs are stable. On physical examination, the physician notes prominent jugular venous distention and a palpable parasternal heave. Auscultation reveals globally decreased breath sounds without inspiratory crackles. A subsequent point-of-care echocardiogram demonstrates marked right ventricular dilation alongside a completely normal left ventricular ejection fraction. Which of the following underlying pathophysiologic mechanisms most likely initiated this patient's cardiac findings?

  1. Hypoxic pulmonary vasoconstrictionAnswer
  2. B
    Impaired left ventricular contractility
  3. C
    Chronic elevation of left atrial pressure
  4. D
    Primary degeneration of the tricuspid valve leaflets
  5. E
    Autoimmune destruction of the alveolar-capillary membrane

Answer

The correct answer is hypoxic pulmonary vasoconstriction.
The correct answer identifies the primary mechanism of cor pulmonale in chronic obstructive pulmonary disease (COPD). In patients with advanced COPD, chronic alveolar hypoxia triggers a physiologic compensatory response known as hypoxic pulmonary vasoconstriction. While this mechanism is beneficial in localized lung disease to optimize ventilation-perfusion matching by redirecting blood to better-oxygenated alveoli, global hypoxia causes widespread, unremitting pulmonary vasoconstriction. Over time, this chronic increased resistance leads to vascular remodeling, pulmonary hypertension, and ultimately right ventricular hypertrophy and dilation (cor pulmonale). The normal left ventricular ejection fraction on the echocardiogram confirms that the right-sided failure is strictly secondary to a pulmonary process rather than left-sided heart disease.

Step-by-Step Solution

1
Analyze the patient's physical examination findings.
The patient exhibits classic signs of right-sided heart failure, including jugular venous distention, lower extremity edema, and a parasternal heave.
Identifying the specific clinical syndrome (isolated right heart failure) is necessary to determine the underlying etiology.
2
Evaluate the echocardiographic data in the context of the physical exam.
The right ventricle is dilated, but the left ventricular ejection fraction is completely normal, ruling out left-sided heart failure as the cause of the systemic venous congestion.
This confirms that the right-sided heart failure is secondary to a pulmonary process (cor pulmonale) rather than a cardiac one.
3
Link the primary pulmonary disease (COPD) to the cardiac findings.
Chronic alveolar hypoxia from advanced COPD causes global pulmonary arterial vasoconstriction, resulting in pulmonary hypertension and eventual right ventricular failure.
Understanding the precise pathophysiologic trigger for cor pulmonale is required to select the correct mechanism.

Key Concept

Cor Pulmonale Pathophysiology
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Topics

Cardiovascular System

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