Evaluation of a risk-scale for drug-induced QT-prolongation in elderly psychiatric inpatients

Abstract

Introduction: QT-time prolongation is an indicator for adverse events, especially in elderly patients due to polypharmacy and multimorbidity. We rated the influence of prescribed medication on QT-time and compared the theoretical risk with observed effects on repolarization time. Methods: Based on two publications that considered the effect of drugs on QT-time, a risk-scale was established. Elderly patients were selected from ECG records and their medication was obtained from medical files. Risk-points of the drugs were summarized to a total score. Using Spearman's correlation analysis, a suggested correlation between risk-score points and severity of QT-prolongation was determined. Results: 174 patients aged from 64 to 76 years (mean ± SD 68.7 ± 4.7; 50.9% women) were included for analysis. They had 295 ECGs (mean 1.7 per patient). Theoretical risk-points correlated significantly with observed QT-time. The Spearman correlation-coefficient was 0.247 (P < 0.01, CI 95%). A lower threshold associated with an increased risk to exceed the critical QT-time of 460 ms was computed by receiver operating characteristics (ROC) analysis, resulting in 5 risk points (AUC = 0.623). Conclusions: Since the theoretical risk for QT-prolongation correlated well with the observed QT time, we recommend the implementation of the risk-scale in clinical practice to improve the safety of pharmacotherapy in gerontopsychiatry. For practical reasons it can be amalgamated with therapeutic drug monitoring.