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Using His bundle electrograms and programmed ventricular stimulation, the effects of chronic amiodarone treatment on induction, morphology, and the rate of ventricular tachycardia (VT) were studied in 17 consecutive patients treated with amiodarone for control of recurrent sustained VT or ventricular fibrilation. Studies were done before and after treatment with amiodarone for an average duration of 5.3 (range 2 to 18) months. During the control study, sustained VT could be induced in 16 patients. VT was initiated by single or double right ventricular (RV) extrastimuli in 14 patients, by double left ventricular (LV) extrastimuli in 1 patient, and by RV burst pacing in 1 patient. Only one pattern (morphology) of VT similar to that of spontaneous VT was induced in 12 patients and two patterns of VT in 4 patients. The average cycle length (CL) (mean ± SD) of induced VT was 325.8 ± 61.2 ms. After amiodarone, VT could be induced in 7 of 17 patients and was initiated by single RV extrastimuli in 5 patients, double RV extrastimuli in 1 patient, and RV burst pacing in 1 patient. In 3 of 5 patients in whom VT could be initiated by single RV extrastimuli, initiation of VT required double RV or double LV extrastimuli in the control study; in 1 of 5 patients VT could not be induced in the control study. Amiodarone induced nonclinical, polymorphic VT in 4 patients in whom only clinical VT could be induced during the control study. Compared to control, the CL of induced VT was significantly longer (322 ± 65.7 vs 416 ± 41.5 ms; P < 0.001). During a follow‐up period ranging from 4 to 53 (mean ± SD; 18.6 ± 11.4) months, VT did not recur in 8 patients with no inducible VT and in 6 patients with persistence of inducible VT. One patient without inducible VT died suddenly; VT recurred in 2 patients, one without inducible VT and one with inducible VT. The results show that programmed stimulation studies late in the course of treatment do not accurately reflect the clinical efficacy of amiodarone in VT.
Reddy et al. (Thu,) studied this question.