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Home > 3-Lead ECG screening for prolonged QT-interval in methadone maintenance therapy clients: a pilot study.

O'Carroll, L and Bury, G (2013) 3-Lead ECG screening for prolonged QT-interval in methadone maintenance therapy clients: a pilot study. Irish Journal of Medical Science , 182 , (Suppl 11) , S495-S496.


Prolonged QT interval is a cardiac arrhythmia which may trigger episodes of ventricular fibrillation in certain individuals. Ventricular fibrillation is potentially deadly, as it prevents the efficient circulation of blood around the body. This study was designed to assess the feasibility of using three lead ECG to monitor the heart rhythms of clients attending clinics for methadone maintenance therapy. Regular methadone consumption demonstrably prolongs QT and QTc intervals1. It is difficult to establish whether this effect is dose-dependent, as prolongation of QT interval may be due to a diverse array of causes. Many risk factors may co-exist in a single client. These factors may interact synergistically or antagonise each other, producing an unpredictable effect on QTc. Notably, many drugs, both prescribed and non-prescribed, affect QTc. A large variety of psychiatric medicines, in particular SSRIs and atypical antipsychotics can provoke prolongation of QTc. This is important because methadone maintenance therapy (MMT) clients are frequently exposed to polypharmaceutical treatment of psychiatric co-morbidities with their substance misuse disorder.

It has been estimated that the rate of deaths due to prolonged QTc in MMT programmes is 0.06 per 100 treatment-years2. This is a significant burden of iatrogenic mortality considering there are around twelve thousand MMT patients in Ireland alone. This study aims to demonstrate the suitability and convenience of 3-lead ECG for the screening of prolonged QT interval in the MMT population. Convenience greatly improves client uptake of screening; and so a fast, reliable screening technology should make an appreciable difference to client safety in the future.

This project focuses on the planning and design of a pilot study which will be conducted to refine methods and instruments for use in the main study. Some key issues addressed over the course of the project related to: site selection, pilot power, sampling methodologies, instrument design, QT screening procedure, operational permissions and the logistics of providing sufficient defibrillators. 

Key outputs of the project included the identification of a pilot site, an agreed pilot sample size, pilot sample selection method, revised study instruments, and a pilot method designed to choose between two distinct client feedback generation modalities for use in the main study. The pilot site was selected after the total number of study sites were recruited in order to select a centre which we felt adequately reflected the demographics of the population, but which was small enough to use without sacrificing too much power from the main study. Potential sites were contacted, and if they expressed interest, they were sent follow up correspondence two to three times weekly, and were also given site visits by researchers, and took part in teleconferences discussing study design. Study instruments were revised constantly in response to clinician feedback arising from the site visits and teleconferences. Operational permissions were sought from the HSE for some state operated clinics to participate. This necessitated modification and resubmission of our application for ethical approval. Pilot screening is expected to begin at the end of September.

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