Electromechanical dissociation. Treatable causes of a dire cardiac emergency.

Electromechanical dissociation (EMD) may be primary, due to disease of the heart muscle itself, or secondary to alterations in loading conditions of the heart. Factors such as internal hemorrhage, acute cardiac tamponade, tension pneumothorax, acute pulmonary embolism, and inflow or outflow obstructions of the heart may be responsible for changes in loading. Myocardial ischemia, myocardial depressant overdose, and other conditions may also contribute to secondary EMD. If detected early, these secondary forms of EMD may respond to treatment. Drugs for resuscitation of a patient with EMD include epinephrine, atropine sulfate, and, in selected instances, calcium.