Comparison of event rates and survival in patients with unexplained syncope without documented ventricular tachyarrhythmias versus patients with documented sustained ventricular tachyarrhythmias both treated with implantablecardioverter-defibrillators

Patients with unexplained syncope and inducible ventricular tachyarrhythmia s during electrophysiologic testing have an increased cardiac mortality rat e. We compared event rates and survival of 178 patients with unexplained sy ncope and no documented ventricular arrhythmias (syncope group) versus 568 patients with documented sustained ventricular tachycardia (VT) or fibrilla tion (VF) (VT/VF group) treated, as part of a lead (Ventritex TVL) investig ation, with similar implantable cardioverter-defibrillators (ICDs) capable of extensive data storage. The 2 groups shared similar clinical characteris tics. The mean follow-up was 11 months for the syncope group and 14 months for the VT/VF group. The mean time from device implantation to first approp riate therapy was similar in the 2 groups (109 +/- 140 vs 93 +/- 131 days, p = 0.40). Actuarial probability of appropriate ICD therapy was 49% and 55% at 1 and 2 years, respectively, in syncope group and 49% and 58% in VT/VF group (p = 0.57), Recurrent syncope was associated with ventricular tachyar rhythmias in 85% and 92% of the syncope group and VT/VF group, respectively (p = 0,54), At 2 years, actuarial survival was 91% in the syncope group an d 93% in VT/VF group (p = 0.85). We conclude that patients treated with ICD with unexplained syncope and induced VT/VF have an equally high incidence of appropriate ICD therapy and low mortality compared with similar patients with documented VT/VF, These findings, plus the high association between r ecurrent syncope and ventricular arrhythmias, indicate that VT/VF are likel y etiologies in selected patients with unexplained syncope and support ICD therapy in such cases. (C)2000 by Excerpta Medica, Inc.