QTc interval measurement and metabolic parameters in psychiatric patients taking typical or atypical antipsychotic drugs: a preliminary study.

Background: Antipsychotic drugs have been associated with prolongation of the QTc interval on the electrocardiogram, and QTc prolongation is, in turn, associated with an increased risk of cardiac arrhythmias and sudden death. Antipsychotic polypharmacy has been implicated in reduced survival, possibly secondary to cardiotoxic effects of antipsychotic medication. Abnormalities of glucose homeostasis, which may be more common in individuals with major mood disorders and schizophrenia, also affect the QTc interval.

Method: We performed detailed assessment of metabolic parameters in 103 psychiatric out-patients, from across the diagnostic spectrum, who had been taking antipsychotic medication (typical, atypical, or a combination thereof) for a minimum of 6 months. We measured the QTc interval in a subset of these patients (N = 65).

Results: Only 2 patients (3%) had a prolonged QTc interval. There was a statistical trend (p = .08) toward a lower QTc interval in patients receiving antipsychotic polypharmacy. QTc interval was associated with age (p = .04) but not with any metabolic parameter.

Conclusion: QTc prolongation in this population is uncommon. There was a significant association between increasing age and QTc interval, but cardiac repolarization was not related to any metabolic parameter. Further large prospective studies of similar patients are needed to confirm these findings.