Mexiletine for refractory-ventricular arrhythmias: results using serial electrophysiologic testing.

Mexiletine was administered during serial drug testing to 35 patients with electrically inducible ventricular arrhythmias and to 6 with recurrent ventricular tachycardia that could not be induced or terminated by programmed cardiac stimulation. All patients had arrhythmias resistant to all conventionally available agents. Electrically induced arrhythmias were completely suppressed during mexiletine therapy in 13 patients. In 12 patients no antiarrhythmic regimen was completely suppressive and in 7 of these mexiletine favorably modified the response to programmed stimulation. In four of six patients with frequent episodes of spontaneous ventricular tachycardia that were not inducible by programmed cardiac stimulation, arrhythmia was controlled by mexiletine. The presence of complete arrhythmia suppression with mexiletine during acute testing accurately predicted long-term freedom from recurrent arrhythmia in 16 of 17 patients over a mean follow-up period of 12.6 +/- 6 months. Severe adverse neurologic effects were noted early during mexiletine therapy in three patients, but no patient discharged on such therapy experienced major adverse effects. The study demonstrates that mexiletine can provide well tolerated effective prophylaxis against recurrent ventricular arrhythmias in a significant proportion of patients resistant to conventional drugs.