In left‑sided heart failure, which factor most directly leads to orthopnea and pulmonary edema?

• A. Elevated left atrial pressure
• B. Tricuspid regurgitation
• C. Right ventricular failure
• D. Peripheral vascular resistance

Answer: (A)

The main concept is that orthopnea and pulmonary edema in left-sided heart failure come from elevated pressure in the left-sided chambers, specifically the left atrium. When the left ventricle fails, blood backs up into the left atrium, raising left atrial pressure and, consequently, pulmonary venous and capillary hydrostatic pressure. This pushes fluid from the capillaries into the interstitium and alveolar spaces, producing pulmonary edema. Lying down increases venous return to the heart, further elevating left atrial pressure and worsening pulmonary congestion, which is why orthopnea occurs.

Tricuspid regurgitation and right ventricular failure involve the right heart and typically cause systemic venous congestion and peripheral edema rather than direct pulmonary edema. Peripheral vascular resistance (afterload) can influence cardiac work but does not directly raise the pulmonary capillary hydrostatic pressure in the setting of left-sided failure, so it’s not the primary driver of orthopnea and pulmonary edema.