Pulmonary Artery Wedge Catheter Position as a Site for Injection of Indicator Substance

Abstract

The pulmonary wedge position is described as a site for injection of indicator-dilution substance because it presents the most central point in the circulation that can be attained during right heart catheterization without actually entering the left side of the heart. Injection at this site furnishes a small "central volume" and produces curves that for the same quantity of dye injected present a sharper peak concentration, a shorter build-up and disappearance time, and therefore a curve the morphology of which is more rigidly set than those obtained by injection at more proximal sites in the right side of the heart. Because the curve is sharper, small recirculation curves on the washout slope are more readily apparent; therefore smaller shunts can be detected during diagnostic cardiac catheterization.