QTc interval screening in an opioid treatment program

Methadone is highly effective for opioid dependency, but it is associated with Torsade de pointes. Although electrocardiography (ECG) has been proposed, its utility is uncertain, because an ECG-based intervention has not been described. An ECG-based cardiac safety program in methadone maintenance patients was evaluated in a single opioid treatment program from September 1, 2009, to August 31, 2011, in the United States. Time from pretreatment to repeat ECG in new entrants was assessed. The proportion with marked rate-corrected QT (QTc) interval prolongation (>500 ms) and the effect of the intervention on the QTc interval in this group were evaluated. Multivariate predictors of QTc interval change were assessed using a mixed-effects model. Of 531 new entrants, 436 (82%) underwent ≥1 electrocardiographic assessment, and 186 (35%) underwent pretreatment ECG. Median time to follow-up ECG was 43 days but decreased over time (p <0.0001). In 21 patients with QTc intervals >500 ms, the mean QTc interval from peak to final ECG decreased significantly (-55.5 ms, 95% confidence interval -77.0 to -33.9, p = 0.001), and 12 of 21 (57.1%) decreased to lower than the 500-ms threshold. In new entrants with serial ECG, only methadone dose (p = 0.009) and pretreatment QTc interval (p <0.0001) were associated with the magnitude of QTc interval change. In conclusion, this study suggests that the implementation of an ECG-based intervention in methadone maintenance can decrease the QTc interval in high-risk patients; clinical characteristics alone were inadequate to identify patients in need of electrocardiographic screening.