Prevalence and Risk Factors for QTc Prolongation in Acute Psychiatric Hospitalization

Prolongation of corrected QT (QTc) interval increases the risk of severe ventricular arrhythmias, in particular torsades de pointes. Patients with severe mental illness (SMI) represent a vulnerable population. This study aimed to measure the prevalence of QTc prolongation in inpatients with SMI and to identify risk factors for QTc prolongation.

Demographic, clinical, anthropometric, laboratory, and electrocardiographic information was extracted from the electronic records of a cohort of patients hospitalized in a psychiatry inpatient unit between July 1, 2017, and July 22, 2019. The primary outcome was the estimation of prevalence of QTc prolongation. The secondary outcome was the identification of risk factors for QTc prolongation.

A total of 597 admissions were included. Only 1.4% had a QTc > 500 msec, while 11.6% had a QTc > 460 msec. The proportion of women with a QTc > 470 msec was 3.6% and men with a QTc > 450 msec was 7.3%. Several risk factors were individually associated with QTc prolongation. In the multivariate model explaining almost one-third of QTc variance, female sex (P = .04), older age (P = .011), heart rate (P < .001), systolic blood pressure (P = .042), potassium (P = .012), hemoglobin (P = .006), number of antipsychotics (P = .026), and treatment with clotiapine (P = .012) and clozapine (P = .003) were associated with QTc length. Several factors beyond pharmacologic treatment identify subjects at risk for QTc prolongation, and polypharmacotherapy does not seem to increase the risk of QTc prolongation.

QTc prolongation was rare in this cohort of SMI inpatients. Most of the risk factors involved in QTc prolongation are unchangeable elements or linked to general medical conditions, and only a few are modifiable factors, including psychotropic treatment.