Clinical significance of new‐onset atrial fibrillation in patients with hypertrophic cardiomyopathy

AIMS: There is limited information about the clinical significance of atrial fibrillation (AF), particularly new‐onset AF, in patients with hypertrophic cardiomyopathy (HCM) in a community‐based patient cohort. This study was carried out to clarify the prevalence and prognostic impact of AF in Japanese HCM patients. METHODS AND RESULTS: In 2004, we established a cardiomyopathy registration network in Kochi Prefecture as a prospective study, and finally, 293 patients with HCM were followed. In the patients' cohort, we recently reported the clinical outcomes including mortality and HCM‐related morbid events. HCM‐related adverse cardiovascular events were defined in the following: (i) sudden cardiac death (SCD)‐relevant events including SCD, spontaneous sustained ventricular tachycardia, and appropriate implantable cardioverter defibrillator discharge; (ii) heart failure (HF) events with the composite of HF death and hospitalization for HF; and (iii) embolic events included embolic stroke‐related death and admission for embolic events. In the present study, we focused on AF and conducted a detailed investigation. At registration, the mean age of the patients was 63 ± 14 years, and 86 patients (29%) had documented AF including paroxysmal AF. Patients with AF at registration were characterized by worse clinical profiles including more advanced age, more symptomatic, more advanced left ventricular, and left atrial remodelling at registration. During a mean follow‐up period of 6.1 ± 3.2 years, a total of 77 HCM‐related adverse events occurred, and the presence of AF at registration was associated with an increased risk of HCM‐related adverse events, particularly heart failure events. During the follow‐up period, an additional 31 patients (11%) had documentation of AF for the first time, defined as new‐onset AF, with an annual incidence of approximately 1.8%, and finally, a total of 117 patients (40%) showed AF. The presence of palpitation and enlarged left atrial diameter, particularly left atrial diameter ≥50 mm, at registration were significant predictors of new‐onset AF. Importantly, the incidence of overall HCM‐related adverse events was further higher in patients with new‐onset AF observed from AF onset than in patients with AF at registration. CONCLUSIONS: In our HCM registry in an aged Japanese community, a significant proportion developed AF. The presence of AF, particularly new‐onset AF, was associated with increased incidence of HCM‐related events. AF may not be just a marker of disease stage but an important trigger of adverse events.