Long-term efficacy of mexiletine alone and in combination with class Ia antiarrhythmic drugs for refractory ventricular arrhythmias.

The efficacy of mexiletine used alone, and in combination with a class Ia antiarrhythmic drug, was assessed in 159 previously drug-refractory patients with ventricular tachycardia (VT) during serial electrophysiologic studies and during long-term (5-year) clinical follow-up. Electrically-inducible ventricular tachycardia was suppressed by mexiletine alone in 23% of patients tested, and a combined antiarrhythmic drug regimen was effective in 29% of the trials performed. Mexiletine was much more likely to be effective in patients presenting with nonsustained VT or ventricular fibrillation than in patients with sustained VT (p less than 0.005). After 1 and 4 years of treatment, 18% and 42% of the patients treated with mexiletine alone had died suddenly or suffered recurrent symptomatic VT, compared to 11% and 25% of patients treated with the combined antiarrhythmic drug regimens (p = NS). Mexiletine therapy was associated with frequent, though readily reversible, adverse reactions. However, mexiletine treatment had to be discontinued permanently in 8 of 92 patients (9%) because of intolerable side effects. We conclude that the added efficacy and possible improved arrhythmia-free survival associated with combining mexiletine with a class Ia agent should be further investigated.