Impact of Atrial Fibrillation on the Clinical Course of Hypertrophic Cardiomyopathy

Abstract: Background Clinical impact of atrial fibrillation (AF) in hypertrophic cardiomyopathy (HCM) is largely unresolved. Thus, we analyzed the prognostic implications of AF in a large, community-based HCM population assembled from Italian and US cohorts. Methods and Results Occurrence of AF and outcome were assessed in 480 consecutive HCM patients (age at diagnosis, 45±20 years; 61% male) who were followed up for 9.1±6.4 years. AF occurred in 107 patients (22%; incidence, 2%/y) and was independently predicted by advancing age, congestive symptoms, and increased LA size at diagnosis. Patients with AF had increased risk for HCM-related death (OR, 3.7; P <0.002) because of excess heart failure–related mortality but not sudden, unexpected death. This risk associated with AF was substantially greater in patients with outflow obstruction or with earlier development of AF (≤50 years of age). AF patients were also at increased risk for stroke (OR, 17.7; P =0.0001) and severe functional limitation (OR for NYHA class III or IV, 2.8; P <0.0001). Compared with those with exclusively paroxysmal AF, patients developing chronic AF showed higher combined probability of HCM-related death, functional impairment, and stroke ( P <0.0001). In a subgroup of 37 patients with AF (35%), the clinical course was largely benign in the absence of stroke and severe symptoms. Conclusions In a community-based HCM population, AF (1) was common, with 22% prevalence over 9 years; (2) was associated with substantial risk for heart failure–related mortality, stroke, and severe functional disability, particularly in patients with outflow obstruction, those ≤50 years of age, or those developing chronic AF; and (3) was nevertheless compatible with benign outcome in 35% of patients.