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Difficulty: EasyCardiovascular System

A 64-year-old woman with a known history of severe emphysema presents to her primary care physician due to progressive swelling in both her legs over the past three weeks. She notes a mild increase in exertional fatigue but denies any recent fever, chills, chest pain, or changes in her baseline chronic daily cough. Her temperature is 37.0°C (98.6°F), blood pressure is 128/78 mmHg, pulse is 96/min, and respiratory rate is 18/min. Pulse oximetry shows an oxygen saturation of 88% on room air. Physical examination reveals a barrel-shaped chest and distant heart sounds. A prominent right ventricular heave is palpated along the left sternal border. When the patient is positioned at 45 degrees, her jugular venous pulsations are visible 6 cm above the sternal angle. Lung auscultation demonstrates globally diminished breath sounds with a prolonged expiratory phase, but no crackles or wheezes are heard. There is 2+ pitting edema in both lower extremities extending to the mid-calves. Which of the following is the most likely underlying pathophysiological mechanism responsible for this patient's new physical examination findings?

  1. Pulmonary arterial vasoconstriction resulting from chronic alveolar hypoxiaAnswer
  2. B
    Impaired left ventricular contractility leading to pulmonary venous congestion
  3. C
    Acute airway inflammation and bronchospasm from a viral respiratory pathogen
  4. D
    Decreased plasma oncotic pressure secondary to significant urinary protein loss
  5. E
    Acute thrombosis within the deep venous system of the lower extremities

Answer

The most likely underlying mechanism is pulmonary arterial vasoconstriction resulting from chronic alveolar hypoxia.
The correct answer accurately describes the mechanism of cor pulmonale. In patients with severe COPD, chronic alveolar hypoxia triggers a physiological reflex known as hypoxic pulmonary vasoconstriction. Over time, this widespread vasoconstriction leads to remodeling of the pulmonary vasculature and pulmonary hypertension. The right ventricle must pump against this increased afterload, eventually leading to right ventricular hypertrophy (manifesting as a right ventricular heave) and right-sided heart failure. Failure of the right ventricle causes backward failure into the systemic venous system, resulting in elevated jugular venous pressure and bilateral peripheral edema. The absence of crackles on lung auscultation helps rule out left-sided heart failure as the cause.

Step-by-Step Solution

1
Analyze the physical examination findings.
The patient has elevated jugular venous pressure, a right ventricular heave, and bilateral peripheral edema, with clear lungs.
These specific signs indicate right-sided volume overload and right ventricular hypertrophy, pointing to isolated right heart failure.
2
Correlate the physical findings with the patient's medical history.
The patient has a history of severe emphysema and demonstrates chronic hypoxia with an oxygen saturation of 88%.
Severe chronic obstructive pulmonary disease (COPD) is a leading cause of right-sided heart failure, a condition known as cor pulmonale.
3
Identify the pathophysiological link between the chronic lung disease and the right heart failure.
Chronic alveolar hypoxia causes reflex pulmonary arterial vasoconstriction.
In the lungs, hypoxia induces vasoconstriction to shunt blood to better-ventilated alveoli. When hypoxia is global (as in severe COPD), it causes widespread pulmonary vasoconstriction, resulting in pulmonary hypertension and subsequent right ventricular failure.

Key Concept

Cor pulmonale is right-sided heart failure caused by pulmonary hypertension secondary to chronic lung disease, most commonly driven by hypoxic pulmonary vasoconstriction.
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Topics

Cardiovascular System

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