EFFICACY OF CLASS-1C ANTIARRHYTHMIC AGENTS IN PATIENTS WITH INDUCIBLEVENTRICULAR-TACHYCARDIA REFRACTORY TO THERAPY WITH CLASS-1A ANTIARRHYTHMIC DRUGS

The efficacy of class 1C antiarrhythmic agents was determined in 36 pa tients with inducible sustained monomorphic ventricular tachycardia du ring baseline electrophysiology study (EPS), who continued to have ind ucible monomorphic ventricular tachycardia during EPS on class 1A anti arrhythmic therapy. Of 12 patients who partially responded to class 1A drugs, 11 (91.7%) continued to have a partial response during EPS on class 1C therapy, whereas one patient did not respond. Of 24 nonrespon ders to class IA therapy, 2 (8.3%) responded during EPS on class 1C th erapy, 7 (29.2%) partially responded, and 15 (62.5%) did not respond. In the 24 nonresponders to class 1A therapy, 9 of 17 patients (53%) wi th left ventricular ejection fraction (EF) greater-than-or-equal-to 30 % responded or partially responded to class 1C therapy, compared with none of 7 patients with EF < 30% (P < .05). The EPS on class 1C agents in patients who fail to respond to class 1A therapy may be warranted only in those with EF greater-than-or-equal-to 30%.