Tricyclic antidepressants in depressed patients with cardiac conduction disease.

The observation that fatalities from tricyclic antidepressant (TCA) overdose are associated with heart block and/or arrhythmias has led to concern about the cardiovascular effects of TCAs. Contrary to expectations, studies have shown TCAs to be relatively safe in patients without heart disease. However, it is unclear whether these drugs are also safe in patients with heart disease. This prospective study compared the risk of cardiovascular complication at therapeutic plasma concentrations of TCAs in 196 depressed patients, 155 with normal electrocardiograms and 41 with either prolonged PR interval and/or bundle-branch block. The prevalence of second-degree atrioventricular block was significantly greater in patients with preexisting bundle-branch block (9%) than in patients with normal electrocardiograms (0.7%). Orthostatic hypotension occurred significantly more frequently with imipramine than with nortriptyline, and in patients with heart disease.