Hypertrophic obstructive cardiomyopathy

The obstruction is caused by increased septal thickness, i.e., hypertrophy, present in the area below the aortic valve ("subaortic"), and by abnormal behavior of the mitral valve (the valve between the left atrium and ventricle), which is larger than normal and moves abnormally (like a "flag"), obstructing normal flow, i.e., the exit of blood from the heart, which often regurgitates into the left atrium ("mitral regurgitation"). This form of HCM is defined as "obstructive." If the obstruction persists for many years and is not resolved, the clinical outcome over time is less favorable than in those without obstruction.

In another 30% of patients, the obstruction occurs only on certain occasions, particularly during exercise, or at the end of a strenuous effort, or even after a large meal, especially if efforts are made after the meal.

Some patients with obstructive HCM report no symptoms or reduced work or exercise capacity. However, the majority develop some symptoms during exertion, such as chest tightness ("angina") and shortness of breath ("dyspnea"), and sometimes even loss of consciousness ("syncope"). These symptoms are usually progressive, meaning they increase over time.

They may improve with appropriate medications. However, patients with significant and persistent symptoms, or with atrial (e.g., atrial fibrillation) or ventricular (e.g., non-sustained ventricular tachycardia) arrhythmias, or progressive left atrial dilation, who do not respond to medical therapy, are candidates for elimination of the obstruction and the often associated mitral regurgitation with appropriate interventions.