Which statement about wedge pressure is true?

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

Answer: (B)

Pulmonary capillary wedge pressure measures left atrial pressure and closely approximates left ventricular end-diastolic pressure, so it serves as an index of left-sided preload. The catheter is advanced into a small branch of the pulmonary artery and wedged to stop blood flow momentarily; the downstream pressure then reflects the pressure in the left atrium, which mirrors LVEDP unless there are mitral valve or severe LV compliance issues. This is why the statement is true: it reflects LVEDP.

It does not measure right ventricular preload—that would be right atrial or central venous pressure. It does not assess systemic vascular resistance, which is calculated from arterial pressure and cardiac output. It does not indicate arterial oxygen content, which comes from arterial blood gas measurements.