Abstract 15802: Baseline Troponin T Levels Modulate the Effects of Implantable Cardioverter Defibrillator Shocks on All-cause Mortality

Introduction: Implantable cardioverter defibrillator (ICD) therapy (shocks or anti-tachycardia pacing (ATP)) has been associated with an increased risk for death. Whether this association is mediated by direct effects of ICD therapy, the underlying myocardial disease process that triggered the tachyarrhythmia, or both remains poorly understood. Methods and Results: We followed 736 patients from the Prospective Observational Study of ICDs (PROSE-ICD) over a median of 5.3 years for the occurrence of ICD therapy and all-cause mortality. Multivariable Cox proportional hazards models were used to calculate the risk-adjusted hazard ratio associated with the different types of ICD therapy, modeled as time-dependent covariates. Additionally, we tested for interaction between ICD shocks and baseline levels of cardiac troponin T (cTnT). Appropriate shock (HR=2.66 [1.77 - 3.98]; p<0.001) was associated with increased mortality, while appropriate ATP (HR=1.02 [0.49 - 2.13]), inappropriate ATP (1.11 [0.48 - 2.58]) and inappropriate shocks (0.81 [0.50 - 1.32]) were not. Independent of the underlying arrhythmia, the mortality effects of ICD shock therapy were strongly modulated by baseline levels of cTnT (p-interaction=0.02). Patients with baseline cTnT≥0.01ng/ml had a significant increased mortality risk associated with ICD shocks (HR=1.73 [1.01 - 2.97] p=0.046) while patients with cTnT<0.01ng/ml did not (HR=0.49 [0.18 - 1.31]). Furthermore, patients with 1 or multiple appropriate shocks and those with multiple inappropriate shocks had a significantly increased mortality risk only in the setting of elevated baseline cTnT≥0.01ng/ml (Figure 1). Conclusions: Elevated baseline cTnT increases the risk of death in patients experiencing ICD shocks regardless of the underlying triggering arrhythmia. These findings provide further insights into how the underlying myocardial substrate may affect the relationship between ICD shocks and all-cause mortality.