Electrocardiographic findings in children and adolescents treated with antipsychotics: a cohort study.

Background/objectives: Antipsychotic drugs are increasingly prescribed in children and adolescents across a wide range of psychiatric conditions. Although cardiovascular adverse effects are generally considered uncommon, concerns about electrocardiographic abnormalities, particularly QTc interval prolongation, have led to ongoing debate regarding appropriate monitoring strategies. Real-world data on the frequency, persistence, and clinical relevance of ECG findings during antipsychotic treatment in youth remain limited. Methods: This was a single-center, observational cohort study including patients younger than 18 years, treated with antipsychotics between January 2020 and December 2024. Inclusion required the availability of at least one 12-lead ECG performed during treatment and accompanied by a cardiology report. ECG parameters were extracted from all available recordings, with QTc calculated using Bazett's formula and interpreted using sex-specific reference thresholds. ECG findings were analyzed primarily at the patient level, defining abnormalities based on their occurrence at any point during follow-up. An exploratory comparison was performed between patients with and without QTc prolongation. Results: The study included 430 patients (79.1% males; mean age 11.3 ± 3.35 years), of whom 429 had analyzable ECG data. At the patient level, 195 of 429 patients (45.5%) exhibited at least one numeric ECG abnormality during follow-up, most commonly heart rate abnormalities. QTc prolongation above sex-specific thresholds was observed in 24 patients (5.6%) and proved to be persistent in only 5 cases (20.8%), defined as occurrence in at least 2 ECG recordings. No patient exhibited a QTc ≥500 ms, and no clinically significant ventricular arrhythmias, high-grade conduction disturbances, or sudden cardiac events were observed. QTc prolongation was not significantly associated with sex, age, antipsychotic polypharmacy, combined first- and second-generation antipsychotic exposure, or QT-relevant comedications. Conclusions: In this large naturalistic pediatric cohort, ECG abnormalities during antipsychotic treatment were relatively frequent but predominantly mild, transient, and clinically benign. QTc prolongation occurred in a small minority of patients and was not associated with adverse cardiac outcomes. These findings may support a selective, risk-based approach to ECG monitoring in children and adolescents treated with antipsychotics, rather than routine universal screening.