Electromechanical dissociation: pathologic explanations in 50 patients

Electromechanical dissociation (EMD), defined as electrocardiographically adequate ventricular systolic complexes in the absence of detectable pulse or blood pressure, may occur in the terminal course of patients and is frequently unexplained. The 50 cases in the autopsy files of The Johns Hopkins Hospital in which the patients had died after documented episodes of EMD were reviewed. Four major categories of patients were identified: In 22 of 50 cases (44 per cent) myocardial ischemia appeared to precipitate EMD; in 14 of these 22 cases (64 per cent) myocardial ischemia was global in extent, while in eight (36 per cent) myocardial ischemia was regional, occurring in the distribution of an occluded coronary artery. A subset of ten patients with ischemia had terminal ventricular tachycardia or fibrillation, which was converted to EMD following resuscitation maneuvers. In 12 of 50 cases (24 per cent) systemic shock preceded the development of EMD; in nine of these 12 (75 per cent) hypotension was due to myocardial or arterial rupture, while in three (25 per cent) hypotension was secondary to sepsis. In ten of 50 cases (20 per cent) pulmonary vascular compromise was the apparent cause of EMD. Of these ten cases, eight (80 per cent) were secondary to pulmonary embolization, and two (20 per cent) were due to pneumothorax. In six of 50 cases (12 per cent) the precise cause of EMD could not be determined. The results of this study indicate that in the dying patient with electromechanical dissociation the differential diagnosis should include myocardial ischemia, systemic shock, and pulmonary vascular compromise.