Sequelae of nonsustained polymorphic ventricular tachycardia induced during programmed ventricular stimulation.

The results of 206 programmed ventricular stimulation studies performed in 130 patients (100 men and 30 women, mean age 62 +/- 12 years, +/- standard deviation) were examined prospectively to determine the sequelae of nonsustained polymorphic ventricular tachycardia (VT) induced during programmed ventricular stimulation. The clinical indication for the electrophysiologic study was either documented monomorphic VT or unexplained syncope. The pacing protocol included 2 right ventricular pacing sites, 2 basic drive cycle lengths and up to 3 extrastimuli. In 111 studies, nonsustained polymorphic VT was induced and with continuation of the programmed stimulation protocol, sustained monomorphic VT was induced in 48 studies (43%) and polymorphic VT was induced in 13 studies (12%). Overall, sustained monomorphic VT was induced in 110 studies and sustained polymorphic VT in 18 studies. The incidence of nonsustained polymorphic VT preceding the induction of sustained polymorphic VT was significantly greater than the incidence of nonsustained polymorphic VT preceding the induction of sustained monomorphic VT (72 vs 44%, p less than 0.05). Nonsustained polymorphic VT is not a useful predictor of the outcome of programmed ventricular stimulation. The use of nonsustained polymorphic VT as an endpoint for stimulation would be likely to improve the specificity of programmed ventricular stimulation by limiting the induction of sustained nonclinical arrhythmias that require countershock, but at the cost of significantly impairing the yield of monomorphic VT.