Contribution of Non-Sustained Ventricular Tachycardia to the Primary Prevention of Sudden Cardiac Death ― Validation of Current Japanese Circulation Society / Japanese Heart Rhythm Society Guideline Recommendations in the Nippon Storm Study ―

BACKGROUND: The prognostic significance of non-sustained ventricular tachycardia (NSVT) in Japanese patients receiving implantable cardioverter defibrillators (ICDs) for primary prevention remains unclear. This study aimed to verify the prognostic value of NSVT as recommended in the 2018 Japanese Circulation Society guideline. METHODS AND RESULTS: We analyzed 638 patients with structural heart disease who received an ICD or cardiac resynchronization therapy with defibrillator for primary prevention in the Nippon Storm Study. Analysis 1 (n=429) evaluated the association between NSVT history and predefined endpoints in patients with ischemic heart disease (IHD) or non-ischemic heart disease (non-IHD) and reduced left ventricular ejection fraction. Analysis 2 (n=357) assessed the prognostic impact of NSVT documented by Holter electrocardiography across 2 subgroups: Subgroup 1, IHD and non-IHD; and Subgroup 2, other cardiac diagnoses. Endpoints included appropriate ICD therapy, electrical storm, ventricular fibrillation (VF), shock therapy, and mortality. In Analysis 1, a history of NSVT was not significantly associated with appropriate ICD therapy or other major adverse outcomes. In Analysis 2, Holter-documented NSVT was independently associated only with appropriate ICD therapy (hazard ratio [HR] 1.82; 95% confidence interval 1.04-3.18; P=0.035). This association was significant in Subgroup 2, but not in Subgroup 1. CONCLUSIONS: NSVT was modestly associated (HR 1.82) with appropriate ICD therapy but not with VF or mortality, suggesting reconsideration of its clinical role.