Hemodynamics in cardiac tamponade

The M-mode through the minor axis in a patient with an anterior and posterior pericardial effusion and tamponade is seen in panel A; during inspiration, the RV fills and the LV becomes smaller; during expiration, the opposite occurs. In the graph in panel B, RVED_d and LVED_d are plotted against one another and demonstrate a negative correlation, a result of reciprocation of the chambers within the pericardium. Since the pericardium is a rigid box, as respiration brings more blood into the RV, there is less room in the LV; blood pools in the inflating lungs during inspiration. This blood plus the increased stroke volume sent to the lungs during RV inspiratory expansion reaches the LV during expiration. As the LV expands, the RV is compressed. During RV expansion, underfilling of the LV results in a drop in pulse pressure perceived as the paradoxical pulse.