Programmed ventricular stimulation: influence of early versus late introduction of a third extrastimulus, a...

The aim of this prospective study was to analyze the yield of early vs late introduction of a third extra-stimulus during programmed ventricular stimulation.

Two randomized protocols of programmed ventricular stimulation were used in 94 consecutive patients with coronary artery disease who were studied because of non-sustained ventricular tachycardia (9.6%), sustained monomorphic ventricular tachycardia (46.8%), ventricular fibrillation (18.1) or syncope (25.5%). During protocol A, a third extrastimulus was introduced during a basic drive cycle length of 500 ms after completion of programmed ventricular stimulation with 1 and 2 extrastimuli during sinus rhythm and paced cycle lengths of 500, 430. 370 and 330 ms. During protocol B, the third extrastimulus was introduced early (after 1 and 2 extrastimuli during sinus rhythm and a paced cycle length of 500 ms). Both protocols began at the right ventricular apex. If sustained ventricular tachyarrhythmia had been induced, the same sequence of programmed ventricular stimulation was repeated at the right ventricular outflow tract.

The overall incidence of induced arrhythmias did not differ between the two protocols. However, the use of the third extrastimulus (both protocols) increased the yield of ventricular fibrillation induction significantly (P < 0.04) compared with ventricular tachycardia induction.

The introduction of the third extrastimulus should be considered only at the end of stimulation protocols (especially in those patients without previously documented sustained ventricular tachyarrhythmias) in order to prevent induction of polymorphic ventricular tachycardia or fibrillation.