Background: Atrial fibrillation (AF), the most common sustained arrhythmia in hypertrophic cardiomyopathy (HCM), is capable of producing symptoms that impact quality of life and is associated with risk for embolic stroke. However, the influence of AF on clinical course and outcome in HCM remains incompletely resolved. Methods: Records of 1558 consecutive patients followed at the Tufts Medical Center Hypertrophic Cardiomyopathy Institute for 4.8±3.4 years (from 2004 to 2014) were accessed. Results: Of the 1558 patients with HCM, 304 (20%) had episodes of AF, of which 226 (74%) were confined to symptomatic paroxysmal AF (average, 5±5; range, 1 to >20), whereas 78 (26%) developed permanent AF, preceded by 7±6 paroxysmal AF episodes. At last evaluation, 277 patients (91%) are alive at 62±13 years of age, including 89% in New York Heart Association class I or II. No difference was found in outcome measures for patients with AF and age- and sex-matched patients with HCM without AF. Four percent of patients with AF died of HCM-related causes (n=11), with annual mortality 0.7%; mortality directly attributable to AF (thromboembolism without prophylactic anticoagulation) was 0.1% per year (n=2 patients). Patients were treated with antiarrhythmic drugs (most commonly amiodarone [n=103] or sotalol [n=78]) and AF catheter ablation (n=49) or the Maze procedure at surgical myectomy (n=72). Freedom from AF recurrence at 1 year was 44% for ablation patients and 75% with the Maze procedure ( P <0.001). Embolic events were less common with anticoagulation prophylaxis (4/233, 2%) than without (9/66, 14%) ( P <0.001). Conclusions: Transient symptomatic episodes of AF, often responsible for impaired quality of life, are unpredictable in frequency and timing, but amenable to effective contemporary treatments, and infrequently progress to permanent AF. AF is not a major contributor to heart failure morbidity or a cause of arrhythmic sudden death; when treated, it is associated with low disease-related mortality, no different than for patients without AF. AF is an uncommon primary cause of death in HCM virtually limited to embolic stroke, supporting a low threshold for initiating anticoagulation therapy.

Background: The relation of sex to clinical presentation and course in hypertrophic cardiomyopathy ( HCM ) remains incompletely resolved. We assessed differences in clinical outcomes between men and women within our large HCM cohort. Methods and Results: Of 2123 consecutive patients, a minority (38%) were women who were diagnosed with HCM at older ages or referred for subspecialty evaluation later than men (50±19 versus 44±16 and 55±18 versus 49±16; P <0.001). Women more commonly developed advanced New York Heart Association class III / IV symptoms (53% versus 35% in men; P <0.001), predominantly secondary to outflow obstruction. While end‐stage heart failure with systolic dysfunction (ejection fraction <50%) was similar in men (5% versus 4% in women; P =0.33), women were 3‐fold more likely to develop heart failure with preserved systolic function (7.5% versus 2.6%; P =0.002). Sudden death events terminated by defibrillator therapy were similar in women (0.9%/year) versus men (1.0%/year; hazard ratio, 0.92; 95% CI , 0.6–1.5; P =0.73). HCM mortality was uncommon, with identical rates in both sexes (0.3%/year; hazard ratio, 1.5; 95% CI , 0.7–3.4;, P =0.25). Age‐adjusted all‐cause mortality also did not differ between women and men (1.7% versus 1.3%/year; hazard ratio, 1.32; 95% CI , 0.92–1.91; P =0.13). Conclusions: Survival was not less favorable in women with HCM . Contemporary treatments including surgical myectomy to reverse heart failure and defibrillators to prevent sudden death, were effective in both sexes contributing to low mortality. However, despite more frequent outflow obstruction, women with HCM are underrecognized and referred to centers later than men, often with more advanced heart failure. Greater awareness of HCM in women should lead to earlier diagnosis and treatment, with implications for improved quality of life.

Background: Atrial fibrillation (AF) is the most common sustained arrhythmia in hypertrophic cardiomyopathy (HCM), associated with impaired quality of life, risk for embolic stroke, and unpredictable onset. We sought to create a predictive model to identify risk for AF development in HCM. Methods: A cohort of 1900 patients with HCM followed for newly diagnosed AF in the Tufts HCM center was used for model development. A cohort of 387 patients from Toronto General Hospital was used for external validation. Data in the development cohort generated the HCM-AF score, a point score to predict AF probability at 2 and 5 years: left atrial dimension (+2 points per 6 mm increase), age at clinical evaluation (+3 points per 10-year increase), age at initial HCM diagnosis (−2 points per 10-year increase), and heart failure symptoms (+3 points if symptomatic). Results: The HCM-AF score stratifies risk as low (2.0%/y; score ≥22) for AF development for individual patients. Concordance of the HCM-AF score was 0.70 in the development cohort and 0.68 in the external validation cohort. In the development cohort, 17.2% of high-risk patients developed AF (rate 3.4%/y), while only 3.3% of low-risk patients developed AF (rate 0.7%/y) at 5 years ( P <0.001). Similarly, in the external validation cohort, 13.3% of high-risk patients developed AF (rate 2.7%/y), whereas only 1.1% of low-risk patients developed AF (rate 0.2%/y). The HCM-AF score provided greater predictive power for future AF risk than left atrial dimension alone (concordance of 0.58) and outperformed other non–HCM risk models. Conclusions: The HCM-AF score is a novel externally validated predictive tool to identify AF risk in HCM. This score can reliably stratify patients with HCM to risk of newly diagnosed AF and offers the opportunity to inform expectations regarding future clinical course.