Pericardial tamponade-induced myocardial ischemic injury.

Cats of either sex anesthetized with sodium pentobarbital (30 mg/kg, IV) were subjected to sham pericardial tamponade or pericardial tamponade for five hours. Five cats underwent sham pericardial tamponade and six cats were subjected to pericardial tamponade which reduced the mean arterial blood pressure to approximately 40 mm Hg. Pericardial tamponade produced a 44-51% and a 28-38% decrease in the myocardial activities of cathepsin D and creatine phosphokinase (CPK), respectively. Observation of cellular and subcellular structure of left ventricular tissue of two sham operated cats and two cats after tamponade revealed myocardial injury in cats subjected to tamponade. Tissue stained with hematoxylin-basic fuchsin-picric acid stain showed extensive crimson-red basic fuchsin staining in cats subjected to pericardial tamponade and the absence of staining in cardiac tissue of sham-operated cats. Electron micrographs of cardiac tissue of cats subjected to acute pericardial tamponade revealed extensive vacuolization and extreme contracture. These results indicate ischemic injury with loss of cellular and subcellular enzymes in hearts of cats after five hours of pericardial tamponade sufficient to reduce the mean arterial blood pressure to about 40 mm Hg.