In invasive hemodynamic monitoring, when wedge pressure cannot be obtained, which PA-derived pressure is commonly used as a surrogate for left atrial pressure?

• A. Pulmonary artery diastolic pressure
• B. Pulmonary artery systolic pressure
• C. Mean pulmonary artery pressure
• D. Central venous pressure

Answer: (A)

When wedge pressure cannot be obtained, the diastolic pressure in the pulmonary artery is commonly used as a surrogate for left atrial pressure. The reason is that during diastole, the pressure transmitted back from the left atrium through the pulmonary circulation is reflected more directly in the PA diastolic pressure, making it a closer approximation to left-sided filling pressures than the systolic or mean PA pressures. Central venous pressure reflects right atrial pressure and not left heart pressures, while PA systolic and mean PA pressures are influenced by right heart function and pulmonary vascular resistance and thus are less reliable as LA surrogates. Use of PA diastolic pressure is practical, but remember it may deviate from true LA pressure in certain pulmonary or left-sided conditions.