• implantable cardioverter defibrillator;
  • syncope;
  • ventricular tachyarrhythmias;
  • electrophysiologic testing

ICD Use in Syncope. Introduction: Implantable cardioverter defibrillators (ICDs) are occasionally used in presumed high-risk patients with electrocardiographically undocumented syncope, although the incidence of ventricular tachyarrhythmias in this population is not well defined.

Methods and Results: We studied 33 consecutive patients receiving; an ICD (67% nonthoracotomy and 70% tiered therapy) after electrophysiologic testing for unmonitored “syncope” (n = 29) or “near-syncope” (n = 4). Atherosclerotic heart disease was present in 24 (73%); mean left ventricular ejection fraction (LVEF) was 0.39 ± 0.15; and sustained monomorphic ventricular tacycardia (SMVT) was inducible in 18 (55%). Over a median follow-up of 17 months (range 4 to 61), 12 patients (36%) received ≥ 1 appropriate ICD discharge triggered by SMVT (cycle length 230 lo 375 msec) in 10 and ventricular Mutter or fibrillation in 2—without concomitant antiarrhythmic medication in 8 of 12 cases, Inducible SMVT and LAEF ≤ 0.35 were statistically significant, independent predictors of an appropriate ICD discharge (P < 0.02 and P < 0.03, respectively). Estimated 1-year cumulative survival free of appropriate discharge was 34% versus 87%, respectively, in patients with versus without inducible SMVT (P < 0.02), and 18% versus 56%, respectively, in patients with LVEF ≤ 0.35 versus LVEF > 0.35 (P < 0.03).

Conclusion: In this highly select, multicenter population of ICD recipients with electrocardiographically undocumented syncope, a substantial incidence of appropriate device discharges was observed, particularly in patients with inducible SMVT and LVEF ≤ 0.35. These findings support the notion that, in patients with LV dysfunction and inducible SMVT, ventricular tachyarrhythmias are likely to account for episodes of syncope or near-syncope.