P2874Predictors of Electrical Strom among ICD patients: the importance of the burden of non-sustained VTs

Abstract

Abstract Background Among ICD patients, the burden of non-sustained ventricular tachycardias (NSVT) occurring during the first 6 months after implant is associated independently with an increase in cardiac death. It is unknown whether there are differences between the incidence of Electrical Storm (ES) and the cause of cardiac mortality (CM) according to the burden of NSVT. Purpose To determine the relationship between the burden of NSVT occurring early after ICD implant and the risk of ES in the long-term among ICD patients with left ventricular dysfunction. Methods In this prospective study, 416 patients (age: 65±11; LVEF: 30±8; ischemic etiology: 62%, primary prevention: 63%) with LVEF <45% and ICD without cardiac resynchronization therapy were followed-up for 41±27 after implant. ICD programming was standardized. NSVT was defined as any ventricular tachyarrhythmia with >5 beats at ≥150 bpm terminating spontaneously before therapy that occurred within the first six months after ICD implant. Results A total of 31 patients (7.5%) presenting with ES during the follow-up. After classifying the subjects into three groups according to the burden of NSVT (tertiles): no NSVT (N=166, group 1); 1–5 NSVT (n=130, group 2) and >5 NSVT (n=120, group 3), the cumulative incidence of ES was higher in group 3: 2.4% vs. 3.1% vs. 19.2%, with an average of time from implant to ES significantly shorter (mean [95% CI, months]): 97 (94–100) vs. 103 (99–106) vs. 86 (79–93); p<0.001 for groups 1–2 vs. 3 (log-rank test). Figure. All ESs were due to monomorphic VT in individuals with ≤5 NSVT; however, 19% of ESs were caused by polymorphic VT or VF among patients with >5 NSVT (p<0.05). By multivariate analysis (Cox-regression), LVEF, % (HR=1.06; p=0.026) and >5 TVNS (HR=4.66; p=0.001) were identified as independent predictors of ES. Cardiac mortality (CM) was independently higher in subjects with >5 NSVT (HR=1.7; p=0.03). The most frequent cause of CM was cardiac failure irrespective of NSVT burden (93% in patients with ≤5 NSVT and 79% in >5 NSVT); however CM due to ES was exclusive of individuals with >5 NSVT: 15% vs. 0% (p<0.05). Figure 1 Conclusions 1. The burden of NSVT occurring during the first 6 months after an ICD implant is associated independently with a higher risk of ES in the long-term. 2. The adjusted risk of ES is 4-fold higher in individuals with >5 NSVT. 3. The most frequent etiology of CM is heart failure; CM due to ES is exclusive of patients with >5 NSVT causing the 15% of deaths in such population.