Antipsychotic drug administration does not correlate with prolonged rate-corrected QT interval in children and adolescents: results from a nested case-control study.

Background: The rate-corrected QT interval (QTc) prolongation is a risk factor for sudden cardiac death and may be induced by antipsychotic drugs.
Objective: To determine the clinical characteristics associated with QTc prolongation (440 msec or greater) in children and adolescents hospitalized for treatment of psychiatric disorders.
Method: We determined the frequency of baseline prolongation of QTc in 811 psychiatric pediatric inpatients (15.5 ± 2.4 years of age). QTc duration was 440 msec or greater (range 441-481 msec) in 16 patients (1.97%). In a 1:5 nested case-control design, the 16 patients with prolonged QTc were age- and gender-matched with 80 patients with QTc of <421 msec.
Results: Patients with normal and prolonged QTc had similar utilization of antipsychotics (43.8% vs. 40.8%) and daily chlorpromazine equivalents (165 ± 110 vs. 168 ± 218 mg). Hypokalemia (p = 0.009) and obesity (p = 0.032) were more common among patients with prolonged QTc. The correlation between obesity and QTc prolongation was confirmed in logistic regression analysis.
Conclusions: In a large cohort of youth hospitalized for treatment of psychiatric disorders, a prolonged QTc on admission was rare and correlated with the presence of obesity, but not with current use of antipsychotic drugs.