Key result
Extended Holter monitoring increases NSVT detection but episodes found after 48 hours fail to predict SCD.
Why the study?
While guidelines recommend 48-hour Holter monitoring for SCD-risk assessment in HCM, extended monitoring (>48-hours) has become commonplace, but the clinical significance of NSVT detected beyond 48-hours remains unclear.
Does nonsustained ventricular tachycardia (NSVT) detected only during extended Holter monitoring (>48 hours) predict sudden cardiac death or appropriate ICD therapy in patients with hypertrophic cardiomyopathy?
Does nonsustained ventricular tachycardia (NSVT) detected only during extended Holter monitoring (>48 hours) predict sudden cardiac death or appropriate ICD therapy in patients with hypertrophic cardiomyopathy?
While extended Holter monitoring in hypertrophic cardiomyopathy increases the detection of NSVT, NSVT found only after 48 hours does not significantly predict sudden cardiac death risk, suggesting NSVT burden is a more relevant prognostic factor.
NSVT detected only after 48 hours should not yet guide SCD risk stratification in HCM; hypothesis-generating for extended monitoring value beyond early detection and burden.
Background Nonsustained ventricular tachycardia (NSVT) predicts sudden cardiac death (SCD) in Hypertrophic Cardiomyopathy (HCM). While guidelines recommend 48-hour Holter monitoring for SCD-risk assessment, extended monitoring (>48-hours) has become commonplace. The significance of NSVT detected beyond 48-hours remains unclear. Purpose This study evaluates the clinical significance of NSVT detection during extended-Holter monitoring in patients with HCM. Methods All patients in a single center HCM registry (2011-2021) were included. NSVT was defined as ≥3 ventricular beats at >100 bpm lasting <30 seconds. Patients were grouped into: Group 1 (No NSVT), Group 2 (NSVT detected <48-hours), and Group 3 (NSVT only detected after >48-hours). The primary endpoint was a composite of SCD or appropriate ICD therapy. Results In 1115 Holter monitors from 413 patients, NSVT was detected in 127 patients (30.8%) within 48 hours and 102 patients (24.7%) only after 48 hours. Among patients with extended-Holter monitoring (n=350), NSVT prevalence increased from 29.1% (102/350) in the first 48 hours to 58.3% (204/350) when considering the extended monitoring period beyond 48-hours (p<0.001). ICDs were implanted in 175 patients (42.4% overall; Group 1: 22.8%, Group 2: 55.9% and Group 3: 60.8%). Over a median follow-up of 5.1 years, 20 patients (4.8%) experienced sudden death/ICD therapy (Group 1:4/184, Group 2:12/127, Group 3:4/102). NSVT within 48 hours carried the highest risk (aHR=4.88, 95%CI 1.55–15.36, p=0.007), while NSVT only found after 48 hours did not show the same prognostic significance (aHR=2.89, 95%CI 0.70–12.01, p=0.14). Among NSVT patients, NSVT burden was the sole predictor of the primary endpoint (adjusted HR=1.78, 95%CI 1.43–2.22, p<0.001). Conclusions In patients with HCM, extended-Holter monitoring increased NSVT detection, though this rarer NSVT detected only with monitoring >48 hours carried less prognostic significance for SCD-risk. Increasing NSVT burden was the only predictive factor for SCD.
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Chaumont et al. (2025) studied this question. Extended-Holter monitoring increased NSVT detection (58.3% vs 29.1%), but NSVT detected only after 48h was not significantly predictive of SCD (aHR=2.89, p=0.14).
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