Which statement about wedge pressure is accurate?

• A. It measures right ventricular preload
• B. It measures systemic vascular resistance
• C. It indicates arterial oxygen content
• D. It reflects left ventricular preload at end diastole

Answer: (D)

Wedge pressure reflects left-sided filling pressures, serving as an indirect measure of left atrial pressure and, in normal conditions, LV end-diastolic pressure. It’s obtained with a balloon-tipped pulmonary artery catheter that is advanced into a small branch of the pulmonary artery and then wedged; the pressure transmitted back from the left atrium through the pulmonary circulation mirrors the left atrial pressure, which corresponds to the preload of the left ventricle at end diastole. This is the key reason the statement is accurate.

It is not a measure of right ventricular preload—that would relate to right atrial central venous pressures. It does not quantify systemic vascular resistance, which requires arterial pressure, central venous pressure, and cardiac output. It also does not indicate arterial oxygen content, which involves oxygen saturation and hemoglobin.