Inappropriate therapies in modern implantable cardioverter-defibrillators: A propensity score-matched comparison between single- and dual-chamber discriminators in single-chamber devices THe sINGle lead Study (THINGS Study).

Background: In patients with implantable cardioverter-defibrillators (ICDs), inappropriate therapies (ITs) are often caused by supraventricular tachyarrhythmias (SVTs).

Objective: We aimed to estimate the incidence of IT in modern single-lead ICDs.

Methods: The THINGS study enrolled patients with single-lead ICDs with 2 SVT discrimination modalities: dual chamber (DC) with an atrial floating dipole or single chamber (SC) with morphology criterion. All devices were programmed with 2-zone therapy: ventricular tachycardia (VT) zone from 170 beats/min with ≥15 seconds (≥36 beats) detection time and SVT discriminators; and ventricular fibrillation (VF) zone from 214 beats/min with ≥7 seconds (≥24 beats) detection time. The primary end point was the first occurrence of IT, adjudicated by an independent board.

Results: A total of 526 patients (median age, 66 years; 83% male), 183 (34.8%) with DC and 343 (65.2%) with SC discrimination, were observed for a median of 2.2 years. The incidence rate of IT was 4.2% (95% confidence interval [CI], 2.7%-6.4%) at 1 year and 7.1% (95% CI, 5.0%-9.9%) at 2 years. Younger age (adjusted hazard ratio, 0.97; 95% CI, 0.95-0.99; P = .013) and history of atrial fibrillation (adjusted hazard ratio, 2.67; 95% CI, 1.30-5.46; P = .007) were significantly associated with increased IT risk. In a propensity score-matched comparison, DC discrimination showed a trend toward reduced IT rates compared with SC discrimination in the VT zone (1-year incidence, 1.8% vs 3.5%; P = .105).

Conclusion: High-rate VF cutoff and prolonged detection time programming resulted in a low IT rate in single-lead ICD patients with modern SVT discriminators. A trend favoring the DC system was observed in the VT zone.