The management of electromechanical dissociation

Abstract

Electromechanical dissociation occurs when there is no effective cardiac output in spite of the presence of a continuing normal or nearly normal electrocardiographic rhythm. A patient with electromechanical dissociation is usually unconscious and apnoeic; no heart sounds are audible, yet electrocardiograpic monitoring shows a continuing rhythm. This paradox has been observed since the earliest days of electrocardiographic monitoring [l] but its precise aetiology and correct treatment remains in many cases obscure. Electromechanical dissociation is a less frequent finding at cardiac arrest than ventricular fibrillation or ventricular tachycardia. In one study of a paramedic-based out of hospital resuscitation service, electromechanical dissociation was present in 13% of 667 cardiac arrests, the remainder being accounted for by asystole (11%) and ventricular tachycardia or fibrillation (76”/u) [2,3]. Greene reports a 5% incidence for EMD in 5199 episodes of out of hospital cardiac arrest in Seattle, 1971-1987 [ 41. Ambulatory monitoring performed during sudden death [5,6] suggests that 25-30X of sudden deaths may be due to electromechanical dissociation or asystole. When cardiac arrest occurs in hospital, electromechanical dissociation appears to be more common, perhaps because the patients have more advanced cardiac disease, and may receive a wider range of drugs during prolonged resuscitation attempts. Raizes [7] found that 15 out of 23 (68%) of in-hospital monitored sudden deaths in the context of acute myocardial infarction were due to electromechanical dissociation. Vincent [8] reported that 36 of 54 (67%) monitored in-hospital cardiac arrests occurred because of electromechanical dissociation, and all were fatal. The prognosis of electromechanical dissociation is very poor, only l/90 patients presenting in one series with electromechanical dissociation surviving to hospital discharge [2]. In the Seattle series [4] survival during long term follow-up in patients where EMD was the arrest rhythm was only 6%. This should be contrasted with the observation that patients resuscitated from ventricular fibrillation during the acute phase of myocardial infarction have a prognosis comparable to those admitted to hospital with uncomplicated myocardial infarction [9].