Previous studies from this laboratory (1-3) have shown that the paradoxical pulse of experimental cardiac tamponade is produced by an exaggerated inspiratory decline of left ventricular stroke volume. Most investigators have concentrated on one of three principal mechanisms of this inspiratory decrease of left ventricular stroke output. An early postulate (4) was that because of high intrapericardial pressure throughout the respiratory cycle, extrapericardial venous pressure falls more than atrial pressure during inspiration, thus reducing cardiac filling and stroke volume (5-7). With this mechanism, inspiratory pulmonary venous pooling would be expected to occur. A second major theory proposes that the tense pericardium is further stretched during inspiration by downward movement of the diaphragm and forward motion of the sternum, increasing cardiac compression and reducing filling of the left heart (8, 9). A third concept depends upon persistence of the normal inspiratory increase in right heart filling during cardiac tamponade. This increase in volume of the right heart and great vessels within the taut pericardial sac is believed to raise the intrapericardial pressure and thus hinder left heart filling by raising left atrial pressure (10, 11).With any of the above three mechanisms, an inspiratory decrease of pressure gradient from pulmonary veins to left atrium would be expected and has been consistently reported (4-7). Thus, additional investigation is required to determine the fundamental mechanism responsible for the paradoxical pulse of cardiac tamponade. In our previous paper (2), exaggerated inspiratory decrease of
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.