Response of QT interval in methadone maintenance treated patients to the rapid changes in heart rate provoked by brisk standing: Comparison to healthy controls and patients with long QT syndrome

Background Patients on methadone maintenance therapy are somehow similar to patients with congenital long QT syndrome (LQTS) because they have malfunction of potassium channels caused by a drug that cannot be easily discontinued. We tested patients on methadone therapy with the "stand-up" test, which has been shown to unravel pathologic QT-prolongation in congenital long-QT patients. Methods "Stand-up" test results of methadone-users, healthy volunteers and congenital LQTS patients were compared. Methadone serum levels and doses were collected. The prognostic value of the test was evaluated after 4 years of follow-up. Results The QT-response of methadone-users to the "stand-up" test resembled that of healthy volunteers more than the response of LQTS-patients. Differences in the QTc of methadone treated patients and controls, which were statistically significant at baseline, became no longer significant after standing. Within 52 months of follow-up, one patient had suffered unexplained death and one had documented ventricular tachycardia. Conclusions The QT-response of methadone-users to the "stand-up" test is similar to that of healthy volunteers, not to that of LQTS-patients.