Which limitation would cause PCWP to no longer accurately reflect LVEDP?

Which limitation would cause PCWP to no longer accurately reflect LVEDP?

• A. Low intrathoracic pressure.
• B. Excessively high systemic vascular resistance.
• C. Obstruction anywhere between the catheter tip and the left ventricle.
• D. High pulmonary capillary pressure.

Answer: (C)

PCWP is used as an indirect estimate of LVEDP because, when the catheter tip is wedged in a distal pulmonary artery, the pressure measured reflects the pressure in the left atrium and, by extension, LVEDP, assuming an unobstructed transmission of pressure through the pulmonary circulation. If there is an obstruction anywhere between the catheter tip and the left ventricle, that pressure signal can’t be transmitted back to the catheter. The wedge pressure then no longer mirrors the actual LVEDP; you’d be reading a pressure governed by the blocked segment or proximal pressures rather than the left-sided filling pressure. That interruption in the transmission is exactly why this limitation makes PCWP unreliable for estimating LVEDP. Other factors might influence measurements in practice, but they don’t inherently break the transmit-contrast concept the way an obstruction along the catheter path does.

PCWP is used as an indirect estimate of LVEDP because, when the catheter tip is wedged in a distal pulmonary artery, the pressure measured reflects the pressure in the left atrium and, by extension, LVEDP, assuming an unobstructed transmission of pressure through the pulmonary circulation. If there is an obstruction anywhere between the catheter tip and the left ventricle, that pressure signal can’t be transmitted back to the catheter. The wedge pressure then no longer mirrors the actual LVEDP; you’d be reading a pressure governed by the blocked segment or proximal pressures rather than the left-sided filling pressure. That interruption in the transmission is exactly why this limitation makes PCWP unreliable for estimating LVEDP.

Other factors might influence measurements in practice, but they don’t inherently break the transmit-contrast concept the way an obstruction along the catheter path does.