A short second coupling interval of NSVT (< 394 ms) poses a higher SCD risk in HCM than a long one, and replacing NSVT with 'malignant NSVT' (NSVT with short second coupling interval) significantly improved SCD risk algorithms.
NSVT occurred in 12.4% of HCM patients in this multicentre cohort, and during a median follow-up of 4.4 years, there were 64 SCDs (2.5%), 159 cardiovascular deaths (6.2%), and 221 all-cause deaths (8.6%).
Among NSVT characteristics examined, the second coupling interval was the best predictor of adverse outcomes, with an optimal cut-off of 394 ms.
A second coupling interval < 394 ms markedly increased the risk of SCD compared to absence of NSVT in both univariable and multivariable analyses.
A second coupling interval ≥ 394 ms did not significantly increase the risk of SCD, cardiovascular death, or all-cause death compared to absence of NSVT.
Replacing conventional NSVT with 'malignant NSVT' (defined as NSVT with a short second coupling interval < 394 ms) significantly improved SCD risk prediction algorithms in HCM.
This was a retrospective, multicentre study of 2625 HCM patients who underwent 24-hour Holter monitoring, with 2584 included in the final analysis.
This research suggests that in patients with hypertrophic cardiomyopathy (HCM), a common inherited heart condition, not all episodes of a specific type of abnormal heart rhythm called non-sustained ventricular tachycardia (NSVT) carry the same risk of sudden cardiac death (SCD). The study followed over 2,500 HCM patients and found that the timing of how quickly an NSVT episode starts — specifically, a measurement called the 'second coupling interval' — is a critical factor. Patients whose NSVT started very quickly (within less than 394 milliseconds) had more than eight times the risk of sudden cardiac death compared to patients without any NSVT, while those whose NSVT started more slowly did not have a significantly elevated risk. Importantly, the study found that how often NSVT occurred or how long each episode lasted did not predict outcomes — only the coupling interval mattered. By relabeling short-coupling-interval NSVT as 'malignant NSVT,' the researchers showed that existing tools used to decide who should receive an implantable cardioverter-defibrillator (ICD) — a device that can shock the heart back into a normal rhythm — could be meaningfully improved. This research suggests that doctors evaluating HCM patients with NSVT on heart monitoring should pay close attention to the specific timing characteristics of these abnormal rhythms, not just whether NSVT is present or absent. Detailed analysis of coupling intervals from Holter monitor recordings could help better identify which patients are at highest risk of sudden cardiac death and may benefit most from an ICD, potentially reducing both under-treatment of high-risk patients and unnecessary device implantation in lower-risk patients.
Zhang Y, Qin F, Guan Y, Wang J, Pu L, Xia Y, et al.. (2026). Associations between specific non-sustained ventricular tachycardia characteristics and sudden cardiac death in hypertrophic cardiomyopathy.. Europace : European pacing, arrhythmias, and cardiac electrophysiology : journal of the working groups on cardiac pacing, arrhythmias, and cardiac cellular electrophysiology of the European Society of Cardiology. https://doi.org/10.1093/europace/euag034