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.