Impact of Atrial Fibrillation on the Clinical Course of Hypertrophic Cardiomyopathy

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.