The cardiovascular safety of the empirical measurement of the seizure threshold in electroconvulsive therapy

Aims and method The Royal College of Psychiatrists' Committee on Electroconvulsive Therapy (ECT) and Related Treatments advises the measurement of initial seizure threshold in all patients undergoing ECT if possible. The subconvulsive electrical stimulation inherent in this process is thought to increase the risk of bradycardia and therefore asystole. Our aim was to establish the prevalence of asystole (no heart beat for 5 or more seconds) during empirical measurement of seizure threshold in patients who had not received anticholinergic drugs, as we were unable to find any published reports of bradycardia or asystole prevalence under these conditions. The electrocardiogram traces of 50 such consecutive patients were analysed later. Results Asystole occurred in 5% of stimulations. Each episode of asystole resolved spontaneously with no adverse outcomes. Contrary to expectations, asystole was no more prevalent in subconvulsive stimulations than in convulsive stimulations. Clinical implications There was no evidence that the empirical measurement of the seizure threshold added to the cardiovascular risk of ECT.