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The clinical significance of sustained nonclinical ventricular tachycardia (VT) induced during electrophysiologic studies was studied in 10 amiodarone-treated patients. Nine patients had previous myocardial infarction while 1 patient had right ventricular dysplasia. All patients had only a single morphologic type of VT recorded during the multiple spontaneous episodes of tachycardia. After serial pharmacological electrophysiologic testing, the patients were placed on antiarrhythmic regimens which included amiodarone in all cases. These drugs did not prevent the induction of nonclinical VT in any of the 10 patients and of sustained clinical VT in 7 patients. Nonclinical VT was sustained, requiring cardioversion (7 patients) or rapid ventricular pacing (3 patients) for termination. After a mean follow-up period of 27 +/- 10 months (range 12 to 36 months), 4 patients did not exhibit recurrent VT, 3 patients with inducible clinical VT experienced a recurrent episode of clinical VT after 16, 27 and 49 months, respectively, 2 patients had nonarrhythmia related deaths after 11 and 12 months, and 1 patient died suddenly after 17 months. These results suggest that laboratory induction of sustained nonclinical VT in amiodarone-treated patients does not imply the likelihood of their future spontaneous occurrence and, therefore, their prevention may not be required.

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