Intravenous mexiletine in management of lidocaine-resistant ventricular tachycardia

Abstract

In coronary care unite, intense activity is directed toward the recognition and suppression of those ventricular arrhythmias which are thought to herald ventricular fibrillation. Ventricular fibrillation is the most common cause of death in the early phase of myocardial infarction, as well as in chronic ischemic heart disease. In some cases it is preceded by ventricular tachycardia, but in others it occurs unexpectedly. Sustained ventricular tachycardia represents a significant problem in the initial care of patients with cardiac disease. Despite comparative safety and effectiveness, lidocaine appears to be less effective during the early phase of acute myocardial infarction.1*2 Although adequate serum levels may often not be achieved with standard doses, in some patients the ventricular arrhythmia appears to be truly “lidocaine resistant.“3*4 Alternative antiarrhythmic drugs, including procainamide, propranolol, and phenytoin, are variably effective. Intravenous disopyramide appears to be an effective antiarrhythmic drug in suppressing serious ventricular arrhythmias, including those not responsive to lidocaine.5 However, the patients with myocardial infarction who have low levels of systemic blood pressure are at increased risk of disopyramide-induced cardiac depression.6*7 Clearly, additional agents are desirable. Mexiletine is a new antiarrhythmic drug, available in oral and intravenous form, that is structurally and electrophysiologically similar to lidocaine. Experimental studies show that it is a quinidine-like drug from group II.8 Clinical studies have shown intravenous mexiletine to be safe and effective in suppressing ventricular arrhythmias that occurred in patients with acute and chronic heart disease as well as in patients with other acute clinical conditions.g-16 This report deals with the clinical evaluation of intravenous mexiletine in a study designed to assess its antiarrhythmic efficacy for emergency treatment of lidoCaine-resistant ventricular tachycardia. A total of 18 patients, 15 men and 3 women, with sustained lidocaine-resistant ventricular tachycardia were entered into the study. Their ages ranged from 40 to 60 years (mean 47 years). Clinical information on these patients is given in Table I. Acute myocardial infarction was present in eight patients; ventricular tachycardia