QTc interval prolongation for patients in methadone maintenance treatment: a five year follow-up study

Background: QTc prolongation for patients in methadone maintenance treatment (MMT) has been reported. In this study we wanted to identify the predictor factors for QTc prolongation >500 ms and other medical risk factors for mortality in this population. Methods: A retrospective chart review study with 55 patients who had previously been included in our performance improvement project and who were eligible to be reviewed. A linear regression model with one-sided p value was used for data analysis. Results: Over 5 years, 41% to 56% of patients had QTc>450 and <500 ms and 4% to 10% of patients had at least one reading of QTc>500 ms. This QTc prolongation from baseline showed statistical significance (p<0.0001). Being diagnosed with congestive heart failure (CHF), elevated HgA1c level and recent cocaine use were significantly associated with QTc prolongation >500 ms. The model as a whole showed statistical significance (F = 3.50, p = 0.02). Being diagnosed with CHF and elevated HgA1c level was significantly associated with mortality. The model as a whole also showed statistical significance (F = 4.63, p = 0.01). Conclusions: This study confirms that methadone may be associated with QTc prolongation. It identified three risk factors for significant QTc prolongation for patients on MMT which are recent cocaine use, uncontrolled blood glucose and CHF. Two of these three risk facts (uncontrolled blood glucose and CHF) were associated with mortality in this cohort. Patients with these medical co-morbidities may benefit from EKG screening and aggressive treatment of the medical risk factors while taking MMT.