The role of combination therapy with mexiletine and procainamide in patients with inducible sustained ventricular tachycardia refractory to intravenous procainamide

Effectiveness and safety of mexiletine in patients at risk for (recurrent) ventricular arrhythmias: a systematic review

While mexiletine has been used for over 40 years for prevention of (recurrent) ventricular arrhythmias and for myotonia, patient access has recently been critically endangered. Here we aim to demonstrate the effectiveness and safety of mexiletine in the treatment of patients with (recurrent) ventricular arrhythmias, emphasizing the absolute necessity of its accessibility. Studies were included in this systematic review (PROSPERO, CRD42020213434) if the efficacy or safety of mexiletine in any dose was evaluated in patients at risk for (recurrent) ventricular arrhythmias with or without comparison with alternative treatments (e.g. placebo). A systematic search was performed in Ovid MEDLINE, Embase, and in the clinical trial registry databases ClinicalTrials.gov and ICTRP. Risk of bias were assessed and tailored to the different study designs. Large heterogeneity in study designs and outcome measures prompted a narrative synthesis approach. In total, 221 studies were included reporting on 8970 patients treated with mexiletine. Age ranged from 0 to 88 years. A decrease in ventricular arrhythmias of >50% was observed in 72% of the studies for pre-mature ventricular complexes, 64% for ventricular tachycardia, and 33% for ventricular fibrillation. Electrocardiographic effects of mexiletine were small; only in a subset of patients with primary arrhythmia syndromes, a relative (desired) QTc decrease was reproducibly observed. As for adverse events, gastrointestinal complaints were most frequently observed (33% of the patients). In this systematic review, we present all the currently available knowledge of mexiletine in patients at risk for (recurrent) ventricular arrhythmias and show that mexiletine is both effective and safe.

Treatment of Ventricular Arrhythmias and Use of Implantable Cardioverter-Defibrillators to Improve Survival in Older Adult Patients with Cardiac Disease

Ventricular arrhythmia (VA) and sudden cardiac death (SCD) are well-recognized problems in the overall heart failure population, but treatment decisions can be more complex and nuanced in older patients. Sustained VA does not always lead to SCD, but identifies a higher risk population and may cause significant symptoms. Antiarrhythmic drugs (AAD) and catheter ablation are the mainstays for prevention of VA, but have not been shown to improve mortality. The value of implantable cardiac defibrillators (ICDs) may be influenced by patient age. This article discusses long-term treatment of VA and the use of ICDs in the elderly.

Medical therapy to prevent recurrence of ventricular arrhythmia in normal and structural heart disease patients

INTRODUCTION

Recurrent ventricular arrhythmias (VA) are a source of significant morbidity in patients without structural heart disease (SHD) and also mortality in patients with SHD. The treatment goals for these two patient populations differ greatly. Areas covered: The secondary prevention of recurrent VA in patients without and with SHD will be reviewed, focusing on clinical data (especially randomized, controlled trials) in the literature as determined through searches in PubMed and ClinicalTrials.gov. This will include β blockers, non-dihydropyridine calcium channel blockers and antiarrhythmic drugs in both subgroups and non-antiarrhythmic medications in SHD. Expert commentary: The available options for medical therapy for VA in both normal hearts and SHD are insufficient, due to substandard efficacy and toxicities. While non-pharmacologic therapies may provide an excellent option, further drug development and randomized trials are needed, as is a reappraisal of the current mode of utilization.

Antiarrhythmic agents: drug interactions of clinical significance

The management of cardiac arrhythmias has grown more complex in recent years. Despite the recent focus on nonpharmacological therapy, most clinical arrhythmias are treated with existing antiarrhythmics. Because of the narrow therapeutic index of antiarrhythmic agents, potential drug interactions with other medications are of major clinical importance. As most antiarrhythmics are metabolised via the cytochrome P450 enzyme system, pharmacokinetic interactions constitute the majority of clinically significant interactions seen with these agents. Antiarrhythmics may be substrates, inducers or inhibitors of cytochrome P450 enzymes, and many of these metabolic interactions have been characterised. However, many potential interactions have not, and knowledge of how antiarrhythmic agents are metabolised by the cytochrome P450 enzyme system may allow clinicians to predict potential interactions. Drug interactions with Vaughn-Williams Class II (beta-blockers) and Class IV (calcium antagonists) agents have previously been reviewed and are not discussed here. Class I agents, which primarily block fast sodium channels and slow conduction velocity, include quinidine, procainamide, disopyramide, lidocaine (lignocaine), mexiletine, flecainide and propafenone. All of these agents except procainamide are metabolised via the cytochrome P450 system and are involved in a number of drug-drug interactions, including over 20 different interactions with quinidine. Quinidine has been observed to inhibit the metabolism of digoxin, tricyclic antidepressants and codeine. Furthermore, cimetidine, azole antifungals and calcium antagonists can significantly inhibit the metabolism of quinidine. Procainamide is excreted via active tubular secretion, which may be inhibited by cimetidine and trimethoprim. Other Class I agents may affect the disposition of warfarin, theophylline and tricyclic antidepressants. Many of these interactions can significantly affect efficacy and/or toxicity. Of the Class III antiarrhythmics, amiodarone is involved in a significant number of interactions since it is a potent inhibitor of several cytochrome P450 enzymes. It can significantly impair the metabolism of digoxin, theophylline and warfarin. Dosages of digoxin and warfarin should empirically be decreased by one-half when amiodarone therapy is added. In addition to pharmacokinetic interactions, many reports describe the use of antiarrhythmic drug combinations for the treatment of arrhythmias. By combining antiarrhythmic drugs and utilising additive electrophysiological/pharmacodynamic effects, antiarrhythmic efficacy may be improved and toxicity reduced. As medication regimens grow more complex with the aging population, knowledge of existing and potential drug-drug interactions becomes vital for clinicians to optimise drug therapy for every patient.