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Study objective Methadone is associated with QT interval prolongation and torsades de pointes. Expert panel recommendations advocate a pre-methadone electrocardiogram (ECG) and another ECG at 30 days of therapy in patients with risk factors. Some guidelines recommend a pre-methadone ECG and routine ECG monitoring in all methadone patients, but this is controversial due to the resources required. Availability of a convenient, less resource-intensive method of ECG monitoring for patients taking methadone is desirable. The objective of this study was to assess the accuracy of a handheld smartphone ECG (iECG) for QT measurement in patients on maintenance methadone therapy in an urban opioid treatment program. Design Prospective study. Setting Urban opioid treatment program. Patients n = 115 patients in normal sinus rhythm who were on steady-state maintenance methadone therapy INTERVENTION: Patients (n = 115) underwent a simultaneous 12-lead ECG and a single-lead iECG. Measurements and main results The first three QT and RR intervals from lead II of the 12-lead ECG and simulated lead I from the iECG were compared using the Bland-Altman analysis of measurement agreement. Mean [± standard deviation) age was 34 ± 11 years; 71% were female, 75% were white. Compared to the 12-lead ECG, the iECG was associated with a QTc bias of - 0.14 ms (SD = 12 ms, 95% CI = -2.4 to 2.1 ms). The absolute mean difference in QTc between the two methods was 9.5 ± 7.1 ms. For identification of patients with methadone-associated QTc prolongation, the iECG performed moderately well [c-statistic 0.97 (95% CI 0.91-0.99); sensitivity and specificity 75% (95% CI 43-95%) and 99% (95% CI 94-99%), respectively]. The positive and negative likelihood ratios of the iECG for identifying patients with methadone-associated QTc prolongation were 77.25 (95% CI 10.69 to 558.18) and 0.25 (95% CI 0.09 to 0.67), respectively, while the positive and negative predictive values were 90% (95% CI 56-99%) and 97% (95% CI 92-99%), respectively. The accuracy of the iECG for identifying patients with QTc prolongation was 97% (95% CI 91-99%). Conclusion A handheld smartphone ECG is accurate for QT interval measurement in patients taking maintenance methadone therapy, and its performance is moderately good for identifying patients with methadone-associated QTc prolongation.

Introduction: Methadone, a racemic mixture of S - and R -enantiomers, prolongs the QT interval and causes torsades de pointes. Methadone has been shown to lengthen late ventricular repolarization, represented by the T peak-Tend interval, which is modulated primarily by I Kr and I Ks . However, it is unknown whether methadone prolongs early ventricular repolarization, represented by the heart rate-corrected J-T peak (J-T peak c) interval, which is regulated primarily by L-type calcium and late sodium currents. In addition, the relationship between stereospecific serum methadone and metabolite concentrations and effects on J-T peak c and T peak -T end intervals are unknown. Hypothesis: 1) Methadone lengthens both J-T peak c and T peak -T end , and 2) Methadone effects on J-T peak c and T peak -T end correlate with serum S - and R -methadone and S - and R -metabolite [ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP)] concentrations. Methods: Patients (n=81) on steady state maintenance methadone therapy at an urban narcotic treatment center who had undergone a pre-methadone 12-lead ECG within the previous 6 months were identified and asked to return for a followup ECG during steady-state methadone therapy. In a subset (n=41), blood was obtained to determine serum S - and R -methadone and S - and R -EDDP concentrations. Results: Compared to baseline, methadone lengthened mean ± SD J-T peak c (225 ± 26 vs 232 ± 28 ms, p=0.02) as well as T peak - T end (80 ±14 vs 90 ± 16 ms, pS -methadone correlated with J-T peak c [R 2 = 0.41 (95% CI 0.11-0.65), p=0.007]. Serum R -methadone concentrations also correlated with J-T peak c [R 2 = 0.47 (0.17-0.68), p=0.002]. In addition, serum concentrations of S - and R -EDDP correlated with J-T peak c [R 2 = 0.39 (0.09-0.63), p=0.01] and [R 2 = 0.38 (0.07-0.62), p=0.02], respectively. There were no significant correlations between serum S - and R -methadone or S- and R-EDDP concentrations with T peak - T end intervals. Conclusions: Methadone lengthens both early and late ventricular repolarization, suggesting that methadone’s ion channel effects may extend beyond inhibition of I Kr . Serum S - and R -methadone and S -and R -EDDP concentrations are associated with effects on J-T peak c intervals.

STUDY OBJECTIVE Methadone is associated with QT interval prolongation and torsades de pointes. The objective of this study was to (a) determine the incidence of QT interval prolongation among patients on maintenance methadone therapy in an urban opioid treatment program (OTP), (b) compare characteristics of patients who developed methadone-associated QT prolongation with those who did not develop QT prolongation, and (c) investigate the relationship between QT interval prolongation and stereospecific serum methadone and metabolite [2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP)] concentrations. DESIGN Prospective study. SETTING Urban opioid treatment program (OTP). PATIENTS n = 93 patients on maintenance methadone therapy in an urban OTP. INTERVENTION Patients underwent a 12-lead electrocardiogram (ECG) prior to initiating methadone and again during steady-state maintenance methadone therapy. In a subset (n = 43), blood was obtained to determine serum (S)- and (R)-methadone and (S)- and (R)-EDDP concentrations, which were compared in patients who developed Bazett's-corrected QT (QTc) prolongation [≥470 ms (men) or ≥480 ms (women) and/or ≥60 ms lengthening from pretreatment value] with those who did not have QTc prolongation. MEASUREMENTS AND MAIN RESULTS Mean [± standard deviation (SD)] age was 36 ± 12 years; 73% were female, and 74% were white. QTc prolongation occurred in 14 (15.1%) patients. Patients who developed QTc prolongation were older (41 ± 13 vs. 35 ± 9 years, p = 0.03) and had a longer pre-methadone QTc compared with those who did not have QTc prolongation (429 ± 11 vs. 420 ± 20 ms, respectively, p = 0.02). Serum (S)-methadone concentrations were higher in patients with QTc prolongation compared to patients without prolongation (199 ± 81 vs. 128 ± 68 ng/ml, respectively, p = 0.01), whereas the difference in serum (R)-methadone concentrations between the groups did not reach significance (189 ± 68 vs. 125 ± 60 ng/ml, respectively, p = 0.08). Serum (R)-methadone concentrations correlated with QTc intervals [R2 = 0.15 (95% confidence interval (CI) 0.11-0.62, p = 0.0009)]. The correlation between serum (S)-methadone concentrations and QTc did not reach significance [R2 = 0.08 (95% CI -0.01 to 0.54, p = 0.06)]. Serum (S)-and (R)-EDDP concentrations were not significantly different between the groups and did not significantly correlate with QTc intervals. CONCLUSIONS Approximately 15% of patients taking maintenance methadone therapy developed QT interval prolongation. Both serum (S)- and (R)-methadone concentrations, but not (S)- or (R)-EDDP, contribute to methadone-associated QT prolongation.