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).

Abstract

In patients with implantable cardioverter-defibrillators (ICDs), inappropriate therapies (ITs) are often caused by supraventricular tachyarrhythmias (SVTs). To estimate the incidence of IT in modern single-lead ICDs. The THINGS study enrolled patients with single-lead ICDs with two SVT discrimination modalities: dual-chamber (DC) via an atrial floating dipole or single-chamber (SC) with morphology criterion. All devices were programmed with two-zone therapy: (i) VT zone from 170 beats-per-minute with ≥15 seconds (≥36 beats) detection time and SVT discriminators, (ii) VF zone from 214 beats-per-minute with ≥7 seconds (≥24 beats) detection time. The primary endpoint was the first occurrence of IT, adjudicated by an independent board. A total of 526 patients (median age 66 years, 83% males), 183 (34.8%) with DC and 343 (65.2%) with SC discrimination, were followed for a median of 2.2 years. The incidence rate of IT was 4.2% (95% CI, 2.7%-6.4%) at 1 year and 7.1% (95% CI, 5.0%-9.9%) at 2 years. Younger age (adjusted HR 0.97, 95% CI 0.95-0.99, P=0.013) and history of atrial fibrillation (adjusted HR 2.67, 95% CI 1.30-5.46, P=0.007) were significantly associated with increased IT risk. In a propensity-score matched comparison, DC discrimination showed a trend towards reduced IT rates compared to SC discrimination in the VT zone (1-year incidence 1.8% vs. 3.5%, P=0.105). High-rate VF cutoff and prolonged detection times 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.