Implantable Cardioverter Defibrillator Utilization Among Device Recipients Presenting Exclusively with Syncope or Near‐Syncope

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Abstract
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.

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