Cardiac Arrhythmias and ECG Abnormalities in Tricyclic Antidepressant Overdose

Abstract

Tricyclic antidepressant [TCA] overdose is associated with cardiac arrhythmias which may occur without warning, sometimes late in the clinical course. Many institutions routinely monitor cardiac rhythm in such patients for up to 72 h. A retrospective study was carried out to analyze the clinical course of such patients with emphasis on cardiac complications. Cases of TCA overdose (38) were reviewed. Fourteen patients (36.9%) were classified as lethargic or stuporous on admission while 23 (60.5%) were either comatose or semicomatose, 9 requiring endotracheal intubation. Patients were continuously monitored an average of 60 h after admission. Admission ECG were abnormal in a high number of cases, the most common abnormalities being sinus tachycardia (43%) and intraventricular conduction defects (24%). Ventricular ectopy was less common (7.8%). ECG abnormalities, with the exception of sinus tachycardia and infrequent premature ventricular contractions were associated with a severely depressed sensorium and disappeared with neurological improvement, usually in 24 h. No arrhythmias were noted after the patient had become alert. Overall mortality was 2.6%, with no deaths in the adult population. After a search of the literature, intensive care unit monitoring is apparently not indicated for prolonged periods once the patient has otherwise recovered from his acute complications of drug overdose.