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Question

Difficulty: EasyCardiovascular System

A 72-year-old man with a 50-pack-year smoking history and severe chronic obstructive pulmonary disease (COPD) comes to the clinic for evaluation of gradually increasing leg swelling over the past month. He reports his baseline shortness of breath with exertion, but he specifically denies waking up at night gasping for air and states he sleeps comfortably completely flat in his bed. Vital signs show a blood pressure of 128/82 mm Hg, pulse of 88/min, and oxygen saturation of 89% on room air. Physical examination reveals a barrel-shaped chest, distended jugular veins, a palpable parasternal heave, and bilateral 3+ pitting edema of the lower extremities. Auscultation of the lungs reveals distant breath sounds and prolonged expiration, but no crackles. Cardiac auscultation reveals distant heart sounds with no S3 gallop. Which of the following is the most likely primary underlying mechanism for this patient's peripheral edema?

  1. Elevated pulmonary vascular resistanceAnswer
  2. B
    Decreased left ventricular contractility
  3. C
    Acute myocardial ischemia
  4. D
    Chronic venous valvular incompetence
  5. E
    Decreased hepatic protein synthesis

Answer

Elevated pulmonary vascular resistance
The correct answer is elevated pulmonary vascular resistance. This patient's presentation of isolated right-sided heart failure (jugular venous distention, parasternal heave, and peripheral edema) in the setting of severe, long-standing COPD is classic for cor pulmonale. Chronic alveolar hypoxia in COPD causes diffuse pulmonary arterial vasoconstriction, a physiological response initially meant to optimize ventilation-perfusion matching by diverting blood from poorly ventilated to better-ventilated alveoli. Over time, this widespread vasoconstriction leads to chronically elevated pulmonary vascular resistance (pulmonary hypertension). The right ventricle must pump against this increased afterload, leading to right ventricular hypertrophy (manifesting as a palpable parasternal heave) and eventual right ventricular failure, which causes systemic venous congestion and peripheral edema.

Step-by-Step Solution

1
Identify the primary clinical syndrome based on the physical examination findings.
The patient has jugular venous distention, a parasternal heave, and peripheral edema, which collectively indicate right-sided heart failure.
Recognizing the isolated right-sided failure is necessary to rule out generalized or left-sided heart failure.
2
Evaluate the patient's symptoms and lung exam to rule out left-sided heart failure.
The absence of orthopnea, paroxysmal nocturnal dyspnea, and pulmonary crackles strongly suggests the left ventricle is functioning normally and is not the cause of the right-sided failure.
Left-sided heart failure is the most common cause of right-sided heart failure, so it must be explicitly ruled out based on the clinical presentation.
3
Connect the right-sided heart failure to the patient's underlying chronic lung disease.
The patient's severe COPD leads to chronic alveolar hypoxia, which triggers widespread pulmonary vasoconstriction and ultimately increases pulmonary vascular resistance.
Understanding the mechanism of cor pulmonale (hypoxia-induced pulmonary hypertension) identifies the correct pathophysiologic cause.

Key Concept

Pathophysiology of cor pulmonale in chronic obstructive pulmonary disease
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Topics

Cardiovascular System

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