Relationship between ease of inducibility of arrhythmia with electrophysiologic testing and response to...

Electrophysiologic studies are an important tool for guiding the selection of an effective antiarrhythmic drug. The purpose of this study was to determine if there was a relationship between the number of extrastimuli necessary to induce arrhythmia and the response to antiarrhythmic drugs. A group of 56 patients with sustained ventricular tachycardia or ventricular fibrillation who were inducible underwent 235 single-drug studies (4.2 per patient). During the control study, one extrastimulus provoked an end point in 12 patients (group 1) and in only two patients (17%) was at least one drug effective. Of the 18 patients requiring two extrastimuli for induction during baseline (group 2), at least one drug was effective in 11 patients (61%). At least one drug was effective in 20 of 26 patients (77%) who required three extrastimuli (group 3). There were no significant differences among the three groups with respect to presenting arrhythmia, presence of coronary artery disease, or left ventricular ejection fraction. When single drugs or a combination of drugs were used, 58% of group 1, 72% of group 2, and 85% of group 3 were rendered noninducible. During a follow-up of 28 to 32 months, yearly recurrence of arrhythmia was 9.4%, 4.6%, and 1.7%, for the three groups, respectively.