The electrocardiographic features of acute cardiac tamponade

To test the hypothesis that the ECG of cardiac rupture is due to acute cardiac tamponade, 27 episodes of cardiac tamponade were produced in 10 open chest dogs. During continuous monitoring of the ECG and the arterial and venous pressures, 10-30 cc of autologous, heparinized blood, or one of several other solutions, were intermittently infused into the pericardial sac until no effective blood pressure was recorded. The characteristic electrocardiographic findings of acute cardiac tamponade were peaked P waves, decrease of QRS complex voltage, left axis deviation of the QRS complex, deep T wave inversions, and ST segment change. With the appearance of electromechanical dissociation, there was a sudden, vagally mediated bradycardia. Because these changes are similar to those observed at the time of cardiac rupture, it was concluded that the electrocardiographic manifestations of cardiac rupture could be attributed to acute cardiac tamponade.