Thickening of the left ventricular myocardium due to chronic pressure overload (hypertension or aortic stenosis), hereditary cardiomyopathy, or infiltrative disease. Sequelae may include diastolic dysfunction, left atrial enlargement, and/or atrial arrhythmias. May be asymptomatic in early stages. As the condition progresses, patients may present with dyspnea, fatigue, palpitations, and syncope or near syncope.