Efficacy and tolerability of mexiletine treatment in patients with recurrent ventricular tachyarrhythmias and implantable cardioverter-defibrillator shocks

Background: Antiarrhythmic treatment of patients with recurrent ventricular tachyarrhythmia, in whom catheter ablation and amiodarone treatment were ineffective or contraindicated, is an unsolved clinical problem. Aim: The study aims to evaluate the efficacy and tolerability of mexiletine in patients with recurrent ventricular tachyarrhythmias and/or electrical storm events, in whom standard treatment strategies failed to prevent ventricular tachyarrhythmia. Methods: We performed a retrospective cohort analysis of all patients treated with mexiletine for recurrent ventricular tachycardia and/or ventricular fibrillation in our institution between January 2011 and September 2015. The primary endpoints were total number of electrical storm events and ventricular tachycardia/ventricular fibrillation (VT/VF) episodes after the beginning of mexiletine therapy. Secondary endpoints were total number of implantable cardioverter-defibrillator (ICD) therapies and discontinuation of the therapy. Events were compared with a matched duration period before initiating mexiletine. Patients served as self-controls. Results: Seventeen patients were included in the study; 11 patients were males. Mean age was 64.2 15.4 years. The median time of mexiletine treatment was eight months (interquartile range [IR]: 1-22 months). The mexiletine dose was 600 mg/day in 13 patients and 400 mg/day in four patients. In four patients the dose was modified during treatment in a range from 400 to 600 mg/day depending on clinical decision. Treatment with mexiletine significantly reduced the number of electrical storm events (14 episodes vs. two episodes; median and IR for 17 patients: 1 [0-1] vs. 0 [0-0], p = 0.0010), VT/VF episodes (285 vs. 74 episodes; median and IR for 17 patients: 7 [5-27] vs. 0 [0-5], p = 0.0115), and ICD interventions (317 interventions vs. nine interventions; median and IR for 17 patients: 10 [5-25] vs. 0 [0-2], p = 0.0006), in comparison with a matched period before initiation of treatment. In 14 out of 17 patients (82%) sufficient tolerability of mexiletine was observed. Only in three (18%) patients severe side effects of mexiletine treatment occurred requiring discontinuation of therapy. Conclusions: Mexiletine was a sufficiently tolerated antiarrhythmic drug in short-term treatment of ventricular tachyarrhythmias in the studied population. Mexiletine may be effective in the treatment of recurring ventricular tachyarrhythmias or electrical storm events.