Effect of oral combination therapy with mexiletine and quinidine on left and right ventricular function

Combination therapy with mexiletine (MEX) and quinidine (Q) may be more efficacious than monotherapy with either drug in suppressing ventricular arrhythmias, but its effects on ventricular performance are not known. Thus, right ventricular ejection fraction (RVEF) and left ventricular ejection fraction (LVEF) and wall motion score (WMS) were assessed in 14 patients with ventricular tachycardia before antiarrhythmic therapy, during MEX and Q monotherapies, and during combination therapy. During monotherapy, the daily doses and serum drug levels were: MEX, 621 mg/day and 3.4 microM/L; Q, 1573 mg/day and 8.3 microM/L, respectively. With combination therapy, the daily doses and serum drug levels were: MEX, 636 mg/day and 3.3 microM/L; Q, 1643 mg/day and 9.5 microM/L, respectively. Drug therapy did not affect group LVEF (drug free = 36 +/- 19%, MEX = 34 +/- 18%, Q = 36 +/- 19%, and combination MEX-Q = 35 +/- 19%), RVEF (drug free = 34 +/- 11%, MEX = 35 +/- 11%, Q = 36 +/- 13%, and combination MEX-Q = 36 +/- 12%), or WMS. Ventricular function reserve was assessed in five patients. Drug therapy did not affect group exercise LVEF (drug free = 44 +/- 14%, MEX = 42 +/- 12%, Q = 43 +/- 13%, and MEX-Q = 45 +/- 12%), RVEF (drug free = 38 +/- 10%, MEX = 40 +/- 11%, Q = 39 +/- 12%, and MEX-Q = 40 +/- 12%), WMS, or exercise duration. Combination MEX-Q therapy did not have a significant effect on exercise performance or ventricular function in seven additional patients in whom no exercise studies were done during monotherapy.(ABSTRACT TRUNCATED AT 250 WORDS)