[Mexiletine in treatment of chronic ventricular refractary arrhythmias (author's transl)]

We studied the antiarrhythmic effect of oral Mexiletine in 20 patients with stable high-frequency ventricular arrhythmias refractory to therapeutic doses of conventional antiarrhythmic therapy. Arrhythmias were classified according to modified grading system of Lown and Wolf. The efficacy of Mexiletine was assessed with use of both the arrhythmic modified classification of Lown and Wolf and count of premature ventricular beats (PVB) from 24 hours ambulatory electrocardiographic recordings. The dose of Mexiletine was 300 mg every 8 hours; 24 hours ECG recordings were obtained in each patient on days 5,15 and 20 during Mexiletine therapy. The worst of tracings before and during Mexiletine therapy was compared. Mean decrease in PVB was 57% (P less than 0.001). The decrease in PVB was more than 80% in 11 patients. Comparison of the grade of arrhythmias disclosed a favorable effect of Mexiletine in 13 patients, a worsening in 1, and no effect in 6. Classification of the most severe arrhythmia revealed a significant decrease from an average grade of 3.05 to 1.75 (P less than 0.01). Before Mexiletine therapy, 40% of our patients were in Class 0 to II and 60% were in Class III or V, whereas during Mexiletine therapy the corresponding proportions were 75% and 25% respectively. Side effects (confusion, tremors, gastro-intestinal complaints) prompted reduction of the dose in 3 patients. Three additional patients had transient minor side effects (dizziness, nystagmus and gastrointestinal disorders) that did not necessitate a change in therapy and 14 patients reported no side effects. In conclusion our data suggest that Mexiletine is an effective agent in the long-term treatment of serious ventricular arrhythmias refractory to other agents. Since Mexiletine therapy is not associated with severe long-term side effects, it should now be possible to determine its role as a first-line drug for treating ventricular arrhythmias.