Highe PAOP

 Q: All of the following will have an elevated Pulmonary Artery Occlusion Pressure (PAOP) EXCEPT?

A) Left ventricular systolic heart failure 

B) Hypertrophic cardiomyopathy 

C) Cardiac tamponade 

D) Large pulmonary embolism 

E) Hypervolemia

Answer: D

Pulmonary artery occlusion pressure (PAOP), is also known as pulmonary capillary/artery wedge pressure (PCWP/PAWP). It estimates the left atrial pressure. It is ideally obtained with patient lying supine and at the end of expiration. The tip of the Pulmonary Artery Catheter (PAC) should be in zone 3 of the lung. Mean is obtained of the three previous readings to get the final reading. The balloon of PAC should be inflated while obtaining PAOP. The inflated balloon obstructs the blood flow through pulmonary artery and creates a static column of blood between the catheter tip and the left atrium. The pressure at both ends of the column gets equilibrates i.e., the pressure at the distal end of the catheter is equal to the pressure of the left atrium. Thus, PAOP is a reflection of left atrial pressure and a surrogate of the left ventricular end-diastolic pressure. 

Any condition that raises left ventricular end-diastolic pressure makes PAOP high. This includes left ventricular systolic or diastolic heart failure (choice A), mitral or aortic valve disease,  hypertrophic cardiomyopathy (choice B), cardiac tamponade (choice C), hypervolemia (choice E), and large right-to-left shunts. 

In contrast, conditions that deescalate or take away the pressure from the static column of blood between the catheter tip and the left atrium decreases the PAOP like hypovolemia, pulmonary veno-occlusive disease, or obstructive shock due to large pulmonary embolism (choice D).

We have put the original article on this concept from Drs. Swan and Ganz in the reference section below.

#hemodynamics

References:

1. Swan HJ, Ganz W, Forrester J, et al. Catheterization of the heart in man with use of a flow-directed balloon-tipped catheter. N Engl J Med 1970; 283:447. 

2. Oliveira RK, Ferreira EV, Ramos RP, Messina CM, Kapins CE, Silva CM, Ota-Arakaki JS. Usefulness of pulmonary capillary wedge pressure as a correlate of left ventricular filling pressures in pulmonary arterial hypertension. J Heart Lung Transplant. 2014 Feb;33(2):157-62. doi: 10.1016/j.healun.2013.10.008. Epub 2013 Oct 11. Erratum in: J Heart Lung Transplant. 2014 Apr;33(4):459. de Oliveira, Rudolf K F [corrrected to Oliveira, Rudolf K F]. PMID: 24268673.