Electrocardiographic and clinical features of tricyclic antidepressant intoxication. A survey of 88 cases and outlines of therapy.

The data of 88 consecutive patients with intoxication due to tricyclic antidepressant drugs were retrospectively surveyed. Apart from sinus tachycardia, temporary electrocardiographic changes developed in 48 patients (55%). These included, in order of their frequency, QTc prolongation (85%), T-wave abnormality (82%), PQ prolongation (19%), widening of QRS with or without bundle branch block pattern (19%), and supraventricular or indefinable tachycardia with wide QRS complexes (8%). The clinical course was more severe in patients with electrocardiographic changes. They were more frequently unconscious and more often required assisted ventilation than those without electrocardiographic changes (p less than 0.001). Hypotension developed in 6 patients within the first hours of poisoning; all had repolarization abnormalities and 3 developed paroxysmal supraventricular tachycardia with aberrant ventricular conduction. All 88 subjects made a good recovery and no haemodynamic problems occurred after the first 12 hours of intoxication. Second and third degree atrio-ventricular block, bradyarrthythmias and asystole were not seen in any of the patients. A prophylactic cardiac pacemaker was inserted in 13 patients with wide QRS complexes and/or prolonged PQ interval, but was never needed for bradyarrhythmias or overdrive pacing.