Symptoms may be absent or minimal and stable throughout life, or progress with disease duration. Early childhood years are typically asymptomatic, but by mid- to late-teenage years, and throughout adulthood, shortness of breath (dyspnea) that worsens with exertion, chest pain (angina), and palpitations become common. Palpitations can indicate benign or life-threatening arrhythmias. Atrial fibrillation is the most common arrhythmia in hypertrophic cardiomyopathy and its incidence increases with disease duration, atrial enlargement, and mitral regurgitation.8,9 Unrecognized or untreated atrial fibrillation can cause thromboembolism and stroke, each a significant cause of comorbidity in hypertrophic cardiomyopathy. A subset of patients experience symptoms of heart failure due to the development of the dilated, burnt-out phase of disease.10