| Summary: | Background: A few studies to evaluate an incidence of bradyarrhythmia in patients with hypertrophic cardiomyopathy (HCM) have been reported. Methods: We enrolled 161 patients with HCM to evaluate their bradyarrhythmia risk, especially the risk of patients who were at risk for sudden cardiac death (SCD) and eligible for implantation of an implantable cardiac defibrillator (ICD). We defined symptomatic bradyarrhythmia requiring a pacing therapy as a bradyarrhythmia event and collected the data on an occurrence of the event after the time of diagnosis of HCM. The incidence of bradyarrhythmia events was compared between patients with ICD indications (ICD-candidate group) and those without (non-ICD-candidate group). Furthermore, we investigated the associated factors with bradyarrhythmia events using a Cox proportional-hazards model. Results: During 5.5 ± 4.4 years follow-up, bradyarrhythmia events occurred in 8% (13 patients) of whole patients, and in 15% of the ICD-candidate group (n = 74). In contrast, only 2 events (2%) occurred in the non-ICD-candidate group. The incidence of bradyarrhythmia in the ICD-candidate group was significantly higher than that in the non-ICD-candidate group (log-rank p = 0.015). In the ICD-candidate group, a Cox proportional-hazards model demonstrated that lower heart rate at the time of diagnosis (HR: 1.072, 95%CI: 1.012 to 1.135, p = 0.018), and an eligibility of ICD implantation for secondary prevention of SCD (HR: 9.092, 95%CI: 2.644 to 31.258, p < 0.001) were significantly associated with future bradyarrhythmia. Conclusions: HCM patients with eligibility for ICD implantation, especially for secondary prevention of SCD, more frequently suffered from bradyarrhythmia events.
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