Adrenaline-responsive electromechanical dissociation.

Electromechanical dissociation (EMD) occurs when there is no detectable blood pressure in the presence of organised electrocardiographic activity. This condition excludes pulseless ventricular tachycardia, and traditionally was thought to result from a failure of electrical depolarisation in the myocardium to elicit mechanical contraction. It is now understood from echocardiographic evidence that 'pseudo-EMD' is more common-where electrical activity is associated with myocardial contractions too weak to sustain a detectable blood pressure [1]. Three cases of EMD in association with subarachnoid haemorrhage (SAH) are described. This form of cardiovascular collapse appears to respond readily to the use of adrenaline. To our knowledge, this has not been reported previously. We suggest that this form of EMD occurs despite adequate myocardial function and results from sympathetic failure with loss of peripheral vascular resistance.