Associations between specific non-sustained ventricular tachycardia characteristics and sudden cardiac death in hypertrophic cardiomyopathy.

AIMS: Non-sustained ventricular tachycardia (NSVT) is a well-established risk factor for sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HCM). However, its characteristics have been overlooked. This study evaluates the prognostic value of NSVT characteristics, particularly coupling intervals, for HCM risk stratification. METHODS AND RESULTS: This retrospective, multicentre study included 2625 HCM patients. Twenty-four-hour Holter recordings were assessed for NSVT and its characteristics (frequency, duration, and coupling intervals). The primary endpoint was SCD; the secondary endpoints were cardiovascular and all-cause death. Two thousand five hundred and eighty-four patients were analysed (49.6 ± 15.2 years; 62.4% male). Non-sustained ventricular tachycardia occurred in 320 (12.4%). During the median follow-up of 4.4 years, there were 221 all-cause deaths (8.6%), 159 cardiovascular deaths (6.2%), and 64 SCDs (2.5%). Among characteristics, the second coupling interval best predicted adverse outcomes (optimal cut-off = 394 ms). Non-sustained ventricular tachycardia frequency and duration were not prognostic. In univariable and multivariable analyses, a second coupling interval < 394 ms markedly increased the risk of SCD [hazard ratio (HR) 8.36, 95% confidence interval (CI) 4.33-16.12, P < 0.001], cardiovascular death (HR 3.64, 95% CI 2.07-6.37, P < 0.001), and all-cause death (HR 3.26, 95% CI 1.97-5.41, P < 0.001) vs. absence of NSVT, whereas a second coupling interval ≥ 394 ms did not. Replacing NSVT with malignant NSVT (NSVT with short second coupling interval) significantly improved SCD risk algorithms. CONCLUSION: A short second coupling interval of NSVT poses a higher SCD risk in HCM than a long one. Detailed dissection of NSVT characteristics may improve decision-making for implantable cardioverter-defibrillator implantation in HCM.