Background: There have been few studies of the clinical features of hypertrophic cardiomyopathy (HCM) in a community-based patient cohort in Japan.
Methods and results: Cardiomyopathy registration was established in Kochi Prefecture and named the Kochi RYOMA (registry of myocardial diseases) study, consisting of 9 hospitals that registered 261 patients with a diagnosis of HCM. At registration, 74 patients (28%) had documented paroxysmal or chronic atrial fibrillation (AF). Although most patients (93%) were in New York Heart Association (NYHA) class I or II, 17 of the 18 patients in NYHA III had AF; 37 of the 74 patients with AF suffered from morbid events (embolism and/or heart failure (HF) admission), and 15 of 19 patients with embolic events had AF prior to or at the time of embolism. Of the 29 patients who had a history of HF admission, 8 had left ventricular systolic dysfunction, and the other 21 patients were hospitalized because of diastolic HF. AF occurred prior to HF in 20 of those 21 patients. Furthermore, 19 of those 20 patients with AF and diastolic HF were hospitalized within 1 year after detection of AF.
Conclusions: In an unselected regional registry, AF was the major determinant of clinical deteriorations in patients with HCM.