Impact of ventricular tachycardia ablation in S-ICD recipients: insights from the multicenter iSUSI registry
Authors: Schiavone M , Gasperetti A , Vogler J , Laredo M , Breitenstein A , Compagnucci P , Ziacchi M , Lavalle C , Palmisano P , Dello Russo A , Di Biase L , Tondo C , Kuschyk J , Tilz R , Forleo G B 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
The recent PARTITA trial showed a net clinical benefit of early ventricular tachycardia (VT) ablation in patients with implantable cardioverter defibrillator (ICD) experiencing appropriate shocks. The PARTITA trial analysis, however, was performed in transvenous ICD recipients and data regarding its generalizability in subcutaneous ICD (S-ICD) recipients are lacking.

Purpose
To test whether VT ablation after an ICD shock or a hospitalization for slow VT impacts long-term clinical outcomes in S-ICD recipients.

Methods
All patients experiencing an ICD shock or a hospitalization for slow VT (index event) in the multicenter, international, physician-initiated, real-world iSUSI (International SubcutaneouS Implantable Cardioverter Defibrillator) registry were included in the study. Time zero was set as time of first ICD shock / slow VT hospitalization. Patients were stratified based on performance of VT ablation after the index event (VTA+ vs VTA- cohorts). The primary outcome was a combination of device-related appropriate shocks, slow VTs, and cardiovascular mortality during follow-up. Secondary outcomes were device-related appropriate shocks, slow VTs and cardiovascular mortality, taken individually.

Results
Among 1701 patients enrolled in the iSUSI registry, n=211 were included in this study (n=178 experiencing appropriate shocks; n=33 with slow VTs). After the index event, n=58 (27.5%) underwent VT ablation (VTA+ cohort). No significant differences regarding baseline characteristics between VTA+ and VTA- cohorts were observed: mean age 47.3±16.0 years (VTA+) vs 47.9±17.0 years (VTA-), p=0.799; males 82.8% (VTA+) vs 82.4% (VTA-), p=0.945; mean LVEF 43.8±13.2% (VTA+) vs 42.3±15.5% (VTA-), p=0.530; underlying ischemic cardiomyopathy 31.0% (VTA+) vs 32.7% (VTA-), p=0.8.19; primary prevention implant 36.2% (VTA+) vs 43.4% (VTA-), p=0.434; median number of shocks at index time n=2 [1-4] (VTA+) vs n=2 [1-3] (VTA-), p=0.590. Over a median follow-up of 17.3 [10.4–34.8] months, the combined primary outcome was experienced by 46 (21.8%) patients (Figure 1). VT ablation performance was associated with significantly lower event rates (8.6% vs 26.8%; HR 0.215 [CI 0.100–0.637]; p=0.004), although only a trend towards significance of cardiovascular mortality was observed (HR 0.168 [CI 0.020–1.252]; p=0.081). Among VT ablation, LVEF and ischemic cardiomyopathy, which resulted significantly associated with the primary combined outcome at univariate analysis, only VT ablation remained significantly associated with the outcome of interest at multivariate analysis (HR 0.264 [CI 0.104-0.672], p=0.005) (Figure 1). Survival analysis plotted using Kaplan Meier curves has been reported in Figure 2.

Conclusions
In a real world registry of S-ICD recipients, VT ablation post ICD shocks or hospitalizations for slow VTs was associated with a combined improved arrhythmic and mortality outcome at long-term follow-up.