MEXILETINE USE FOR VENTRICULAR TACHYCARDIA REFRACTORY TO STANDARD ANTIARRHYTHMIC THERAPY IN THE ICD ERA

Abstract

The optimal management of patients with who have refractory ventricular tachycardia (VT) despite standard antiarrhythmic drug (AAD) therapy is uncertain. The aim of this study was to describe the use of Mexiletine in a tertiary referral centre and explore its efficacy and safety in the modern ICD/VT ablation era. We conducted a retrospective cohort study of ICD recipients with an ejection fraction of <40% who were initiated on Mexiletine for refractory VA. Patients were identified through the hospital pharmacy database and clinical events were tracked through hospital records by reference to patient charts, and on-line databases. Patients were followed for up to 12 months or until a clinical event. The primary efficacy outcome was a composite of any appropriate ICD shock/sustained VT, VT ablation, or cardiac transplant/LVAD for refractory VT or documented arrhythmic death. Safety endpoints were the discontinuation of Mexiletine due to adverse reactions, hospitalization for congestive heart failure and non-arrhythmic death or death of unknown etiology. We identified 56 patients suitable for analysis on the basis of clearly documented details on the initiation of Mexiletine, and complete follow up till a clinical event or up to 12 months. The median follow up was median follow-up was 76 (2-365) days. The primary outcome occurred in 32 patients (57%) at a median of 39 (2-338) days following initiation of Mexiletine (Figure). Fourteen patients (25%) received an appropriate ICD shock and 9 patients had VT treated by ATP. Nine (16%) of patients underwent VT ablation at a median of 6 (2-101) days. A primary safety outcome occurred in 12 (21%) patients at a median of 41 (6-350) days. Four patients (7%) developed decompensated heart failure. Five patients developed adverse reactions attributed to mexiletine including, ataxia; hypotension; confusion; paraesthesia and nausea. Eleven patients (20%) remained free of clinical events at 12 months. Mexiletine has limited efficacy when used as adjunctive antiarrhythmic therapy for refractory VT. The safety profile appears reasonable in this highly morbid population. A high rate of treatment failure emphasizes the need for improved therapeutic options in this patient population. Randomized studies of Mexiletine in the contemporary ICD era may be useful.