In a patient with cor pulmonale secondary to COPD, the central venous pressure is markedly elevated yet cardiac output is low. Which hemodynamic principle explains this dissociation?

• A Increased venous capacitance reducing venous return
• B Right ventricular afterload elevation shifting the RV operating point to the right on the Starling curve ✓
• C Pulmonary arterial vasodilation reducing RV systolic pressure
• D Left ventricular diastolic dysfunction reducing filling

Explanation

Cor pulmonale elevates pulmonary vascular resistance, dramatically increasing RV afterload. The RV, unable to overcome this resistance, dilates and fails, shifting its operating point to the descending limb of the Starling curve — thus high filling pressure (high CVP) coexists with low stroke volume (low CO). This is right heart failure from pressure overload. Option A is incorrect as COPD does not primarily increase venous capacitance, and option C is opposite; option D may coexist but is not the primary explanation.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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