In a patient with chronic lung disease and elevated pulmonary vascular resistance, which heart chamber is most stressed?

• A. Left atrium
• B. Left ventricle
• C. Right atrium
• D. Right ventricle

Answer: (D)

When pulmonary vascular resistance is high, the right ventricle must push blood through the lungs against a tougher, higher-pressure system. In chronic lung disease, hypoxic vasoconstriction and vascular remodeling raise pulmonary artery pressures, increasing afterload specifically on the right ventricle. The right ventricle responds by working harder, often enlarging and thickening (right ventricular hypertrophy) and, over time, failing—this pattern is called cor pulmonale. The left atrium and left ventricle handle the systemic circulation and aren’t directly overloaded by elevated pulmonary pressures, so they aren’t the chamber under the greatest stress in this scenario. Thus, the right ventricle is the most stressed.