Usefulness of oral quinidine-mexiletine combination therapy for sustained ventricular tachyarrhythmias as assessed by programmed electrical stimulation when quinidine monotherapy has failed.

In patients presenting with sustained ventricular tachyarrhythmias, when oral quinidine monotherapy fails as determined by programmed electrical stimulation, the degree of benefit observed with combination therapy with mexiletine is debated. We prospectively studied 20 consecutive patients (16 men and 4 women) aged 33 to 77 years (mean age, 62 +/- 11 years) who were treated with maximally tolerated quinidine and mexiletine combination therapy and who had ventricular tachyarrhythmias induced at baseline and during oral quinidine monotherapy. Coronary artery disease was present in 19 patients (95%). Programmed electrical stimulation was performed at 2 drive train cycle lengths with up to 3 extrastimuli at two ventricular sites. During follow-up study with combination quinidine-mexiletine therapy ventricular tachyarrhythmias were rendered noninducible in four patients (20%). The remaining 16 patients showed a significant slowing of their tachycardia cycle length (267 +/- 56 msec baseline vs 320 +/- 75 msec with quinidine vs 345 +/- 53 msec with combination therapy, p < 0.05). There was also an increase in the mean QTc interval (452 +/- 50 msec baseline vs 477 +/- 79 msec after quinidine vs 486 +/- 65 msec with combination quinidine-mexiletine therapy, p = not significant) and in the mean ventricular effective refractory period (246 +/- 25 msec baseline vs 281 +/- 37 msec after quinidine vs 290 +/- 25 msec with combination quinidine-mexiletine therapy, p < 0.05). We conclude that sustained ventricular tachyarrhythmias induced during quinidine monotherapy were rendered noninducible by oral combination therapy with quinidine-mexiletine in 20% of cases.(ABSTRACT TRUNCATED AT 250 WORDS)