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

Background Sudden cardiac death (SCD) has been regarded as one of the most devastating complications in patients with hypertrophic cardiomyopathy (HCM)[1]. Non-sustained ventricular tachycardia (NSVT) is a well-established independent risk factor for SCD in patients with HCM, and it has been incorporated into the existing SCD risk models[1,2]. However, these models simply consider the presence or absence of NSVT, overlooking the weight of its specific characteristics. Previous studies on the associations VT characteristics with SCD risk in patients with HCM have reached conflicting conclusions. Current guidelines have also not reached a consensus on the prognostic value of these characteristics[1,3], illustrating the complexity of their relationship between NSVT characteristics with SCD risk in patients with HCM have reached conflicting conclusions. Current guidelines have also not reached a consensus on the prognostic value of these characteristics[1,3], illustrating the complexity of their relationship. Purpose This study comprehensively evaluates the prognostic value of NSVT characteristics for HCM risk stratification. Methods This multicenter study included 2,625 HCM patients. Twenty-four-hour Holter recordings were assessed for NSVT and its characteristics, including frequency, duration, and the first, second, third, and the last first, second, and third coupling intervals. The endpoint of this study was SCD. Results A total of 2,584 patients with available follow-up data were finally analyzed (mean age 49.6 ± 15.2 years; 62.4% male). NSVT occurred in 320 (12.4%) patients. During the median follow-up of 4.4 years, 64 (2.5%) patients experienced SCDs. The second, third, and last third coupling intervals were significantly shorter in the SCD group than in the non-SCD group, while the frequency, duration, and the first, last first, and last second coupling intervals of NSVT were comparable between the SCD and non-SCD groups. Among these characteristics, the second coupling interval best predicted SCD (P < 0.001), with an optimal cutoff of 394ms. A second coupling interval < 394ms markedly increased the risk of SCD (adjusted hazard ratio [HR] 7.496, P < 0.001) compared to patients without NSVT, whereas a second coupling interval ≥ 394ms did not. Replacing NSVT with malignant NSVT (NSVT with a short second coupling interval) in the HCM Risk-SCD model significantly improved its performance (C-statistic 0.700 to 0.723, P = 0.024). Conclusions 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 the decision-making for implantable cardioverter-defibrillator implantation in HCM.