Discordant results of programmed ventricular stimulation at different right ventricular sites in patients with and without spontaneous sustained ventricular tachycardia: a prospective study of 56 patients.

Programmed ventricular stimulation (PVS) was prospectively performed in 56 consecutive patients from both the right ventricular (RV) apex and the RV outflow tract. Thirty-seven patients had documented clinical sustained ventricular tachycardia (VT) and 19 patients had no sustained spontaneous VT in the absence of antiarrhythmic drugs. The sensitivity of VT induction was 65% from the RV apex, 76% from the RV outflow tract and was 89% with combined stimulation at both RV sites. The specificity from the RV apex, the RV outflow tract and both sites combined was 100%. When sustained VT was induced from both sites (51%), it was usually of the same morphologic characteristics, axis and cycle length. When sustained VT was induced at 1 site and nonsustained VT at the second site, the morphologic characteristics or axis usually differed. Of patients who had VT induced at both RV sites during the baseline study 37% had VT rendered noninducible during treatment with conventional antiarrhythmic agents. No patients whose VT was induced at only 1 RV site responded to conventional drugs. We conclude that programmed ventricular stimulation at a second RV site is frequently helpful in the evaluation of VT. Inducibility at only 1 of 2 RV sites predicts a poor response to conventional antiarrhythmic drugs.