EVALUATION OF THE NEED TO MODIFY ANTIARRHYTHMIC THERAPY BECAUSE OF DRUG INTOLERANCE OR INEFFICACY IN PATIENTS EVALUATED BY ELECTROPHYSIOLOGY STUDY

The incidence of recurrent ventricular tachycardia (VT) and drug intol erance after therapy guided by electrophysiology study (EPS) leading t o a change in antiarrhythmic therapy is unknown. To explore this issue , we studied 138 patients undergoing EPS with a serial drug-testing pr otocol. Patients were followed for 24 +/- 21 months (range 1 to 91 mon ths) for recurrent VT, drug intolerance, or both. At baseline EPS, sus tained VT (76%), nonsustained VT (20%), and ventricular fibrillation ( 4%) were induced. On discharge antiarrhythmic therapy, 70 (51%) patien ts were noninducible (<16 beats) and 68 (49%) patients remained induci ble. Of the 138 patients, 56 (41%) required modification of antiarrhyt hmic therapy (change in drug or dose) for recurrent VT (n = 20) or dru g intolerance (n = 36). These events occurred early during follow-up ( 8 +/- 12 months). Patients who were rendered noninducible had a greate r likelihood of remaining free of antiarrhythmic modification than pat ients who remained inducible at 1-year (68% and 60%, respectively) and 2-year (63% and 52%, respectively) follow-up examinations (p < 0.05). Likewise, the noninducible patients had a greater likelihood of remai ning free of recurrent VT than inducible patients at 1-year (95% and 8 0%, respectively) and 2-year (92% and 80%, respectively) follow-up tes ting (p < 0.025). In contrast, the likelihood of remaining free of dru g intolerance was similar between inducible and noninducible patients at 1 year (72% and 75%, respectively) and 2 years (69% and 65%, respec tively). We conclude that antiarrhythmic therapy guided by EPS require s early modification in more than 40% of patients during follow-up. In addition, inducible patients require a change in antiarrhythmic thera py more frequently than noninducible patients because of higher incide nce of recurrent VT.