Pericardial tamponade and its effect on cardiac performance in absence of the pulmonic valve.

A controlled study was undertaken to quantitate and compare the amount of accumulated pericardial fluid causing acute pericardial tamponade in animals with or without an intact pulmonary valve. In 13 mongrel dogs, acute pericardial tamponade was induced by gradual loading of the pericardial cavity with fluid (mean 21.3 cc/m2). In 10 dogs (Group A) the pulmonic valve was completely excised under caval occlusion and the pericardium resealed. In Group B, the control group (n = 3), caval occlusion was performed for the same period of time but the pulmonary valve was left intact. Reloading of the pericardium with fluid in both groups revealed that whereas in the Control Group B a similar volume of fluid was required (mean 213 cc/m2) to cause critical tamponade, in Group A a much smaller volume (mean 132 cc/m2) (40% decrease) now produced tamponade (p less than 0.001). The results of the study may have important practical implications in patients having cardiac operations in which the pulmonary valve is left incompetent, such as after complete repair of tetralogy of Fallot.