Electromechanical dissociation in human beings: an echocardiographic evaluation.

Electromechanical dissociation (EMD) has been described as "organized electrical depolarization of the heart without synchronous myocardial fiber shortening and, therefore, without cardiac output." However, little evidence demonstrating this description exists. We wished to determine whether mechanical activity is present during EMD. Twenty-two patients presenting with, or subsequently developing EMD in the emergency department from April 1986 to January 1987 were studied. Echocardiograms were performed during five-second pauses in CPR, using the subxiphoid approach. Nineteen patients (86%) had synchronous myocardial wall motion. In two others, there was a rhythmic change in the echocardiographic density of the myocardium, without visible chamber narrowing. In one there was no visible myocardial response associated with the QRS complex. One or more cardiac valves were visualized in 17 patients. Of these, valvular motion was seen in 15 (88%), but only four exhibited visible valve closure. In our study population, the majority of patients in EMD had myocardial wall and valve motion. Thus, the term "electromechanical dissociation" may be a misnomer.