IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR UTILIZATION AMONG DEVICE RECIPIENTS PRESENTING EXCLUSIVELY WITH SYNCOPE OR NEAR-SYNCOPE

ICD Use in Syncope. Introduction: Implantable cardioverter defibrillat ors (ICDs) are occasionally used in presumed high-risk patients with e lectrocardiographically undocumented syncope, although the incidence o f 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 electrophysiolog ic testing for unmonitored ''syncope'' (n = 29) or ''near-syncope'' (n = 4). Atherosclerotic heart disease was present in 24 (73%); mean lef t ventricular ejection fraction (LVEF) was 0.39 +/- 0.15; and sustaine d monomorphic ventricular tachycardia (SMVT) was inducible in 18 (55%) . Over a median follow-up of 17 months (range 4 to 61), 12 patients (3 6%) received greater than or equal to 1 appropriate ICD discharge trig gered by SMVT (cycle length 230 to 375 msec) in 10 and ventricular flu tter or fibrillation in 2-without concomitant antiarrhythmic medicatio n in 8 of 12 cases. Inducible SMVT and LVEF less than or equal to 0.35 were statistically significant, independent predictors of an appropri ate ICD discharge (P < 0.02 and P < 0.03, respectively). Estimated 1-y ear cumulative survival free of appropriate discharge was 34% versus 8 7%, respectively, in patients with versus without inducible SMVT (P < 0.02), and 18% versus 56%, respectively, in patients with LVEF less th an or equal to 0.35 versus LVEF > 0.35 (P < 0.03). Conclusion: In this highly select, multicenter population of ICD recipients with electroc ardiographically undocumented syncope, a substantial incidence of appr opriate device discharges was observed, particularly in patients with inducible SMVT and LVEF less than or equal to 0.35. These findings sup port the notion that, in patients with LV dysfunction and inducible SM VT, ventricular tachyarrhythmias are likely to account for episodes of syncope or near-syncope.