Predictors of subcutaneous ICD shocks and prognostic impact in patients with structural heart disease.

Abstract Background We aimed to assess long-term outcomes in S-ICD recipients with structural heart disease, especially focusing on shock incidence, predictors and associated prognoses. Methods In this multicenter registry-based study, we retrospectively included all patients who underwent S-ICD implantation in 3 tertiary centers. The prognostic impact of S-ICD shock was assessed with a composite outcome that included all-cause death and hospitalization for heart failure. Results A total of 351 patients with underlying cardiomyopathy were included. In multivariable Fine and Gray regression models, secondary prevention, LVEF, conditional shock threshold, and QRS duration appeared to be independent predictors of appropriate S-ICD shock occurrence. In the multivariate Cox regression model adjusted for age, baseline LVEF, underlying cardiomyopathy subtype, NYHA class and appropriate shocks were significantly associated with increased composite prognostic outcome risk (HR: 2.61, 95% CI: 1.21 to 5.65, p=0.014), whereas inappropriate shocks were not(HR: 1.35, 95% CI: 0.75 to 4.48, p=0.18) . The analysis of each component of the composite prognostic outcome highlighted that the occurrence of appropriate shocks was associated with an increased risk of hospitalization for heart failure (HR: 3.10, 95% CI: 1.26 to 7.58, p=0.013) and a trend for mortality (HR: 2.19, 95% CI: 0.78 to 6.16, p=0.14). Conclusions Appropriate S-ICD shocks were associated with a 3-fold increase in acute heart failure admission, whereas inappropriate shocks were not. Conditional shock threshold programming is an independent predictor of S-ICD shock, and its prognostic impact should be further investigated in patients with structural heart disease.