Electrophysiologic parameters to predict clinical recurrence of ventricular tachycardia in patients under electrophysiologic study-guided effective pharmacological therapy

Although an electrophysiologic study (EPS) is the most reliable method for selecting the treatment for a patient with sustained ventricular tachycardi a (VT), VT recurrence may occur even during EPS-guided effective therapy. E lectrophysiologic parameters were compared between patients with and withou t arrhythmic events under EPS-guided effective therapy to identify the pred ictive parameters of VT recurrence during the clinical course. The study po pulation consisted of 77 consecutive patients with sustained VT who were re ceiving long-term pharmacological therapy that was demonstrated to be effec tive by the EPS assessment. The VT induction protocol employed 1-3 extrasti muli and rapid ventricular pacing at 2 right ventricular sites and 1 left v entricular site, and isoproterenol was infused when VT was not induced. To determine the 'effective' antiarrhythmic drug, all sustained ventricular ar rhythmias had to be prevented during the whole induction protocol, but repe titive ventricular responses (RVR) were allowed to remain for up to 5 beats when they were in the same QRS configurations as the clinical VT and up to 12 beats when they were in polymorphic QRS configurations. The effective r efractory periods (ERPs) at the 3 ventricular pacing sites and their differ ence (ie, ERP-dispersion) and the maximum number of RVR beats were evaluate d in an EPS during the control state and at the time of drug assessment. In the comparison of patients with and without VT recurrence, there was no si gnificant difference in clinical characteristics or ERPs, but the Delta ERP -dispersion (ie, the increase in ERP-dispersion caused by the antiarrhythmi c drug) and the maximum number of RVRs were significantly smaller in the gr oup of patients without VT recurrence (Delta ERP-dis, -3@8 vs 6@12, p=0.002 7; maxRVR, 3@3 vs 5@4, p=0.0160). The VT recurrence rate was significantly lower in the patients with Delta ERP-dis less than or equal to 0 or maxRVR <6 in comparison with the others (p=0.0114 and p=0.0360). Patients with VT recurrence showed greater Delta ERP-disp and a longer duration of RVRs at t he time of drug assessment in comparison with the patients without VT recur rence. The prognosis of patients under EPS-guided therapy may be improved b y the use of stricter criteria for drug assessment in the EPS, although thi s may decrease the number of drug responders determined in the EPS.