There are two classifications of HCM: Non Obstructive and Obstructive.
Non Obstructive HCM (30% of patients) is the less common formand means that the heart muscle is thickened but is not interfering with blood flow out of the left ventricle. The distribution of the hypertrophy can vary to be focused in one area of the septum or apex (bottom of the heart), or evenly distributed throughout the left ventricle.
Obstructive HCM (70% of patients) occurs when the blood flowing out of the left ventricle is partially blocked by a thickened ventricular septum protruding into an area called the outflow tract. This obstruction can occur at rest or develop/worsen with exercise. The thickening of the septum can also affect the functioning of the mitral valve causing it to be “leaky”, leading to mitral valve regurgitation. This can result in high pressures in the left ventricle because of the force that needs to be generated to get the blood through a narrow outflow tract with each heartbeat.
Facts about HCM:
- HCM is an inherited condition that occurs in approximately 1 in 500 people
- HCM is equally distributed among men and women
- HCM can develop in people at any age
- HCM is the leading cause of death in the young
- HCM may or may not cause symptoms
What are the symptoms of HCM?
The onset and severity of symptoms vary from person to person. Some people experience symptoms and others may never experience symptoms. Typical symptoms include:
- Shortness of breath
- Chest pain
- Dizziness or lightheadedness
- Fainting (syncope)
- The first symptom of HCM may be cardiac arrest or sudden cardiac death
The diagnosis of HCM is made by a combination of ECG, echocardiogram and history and physical examination by a physician. Many HCM patients have a heart murmur on examination as the first clue to diagnosis. Others may come to attention because of symptoms, or a known family history of HCM or sudden cardiac death. Since HCM is an inherited condition, a detailed family history is an important part of the initial evaluation. Genetic testing is available for HCM patients and can help provide a definitive diagnosis and is a highly valuable and efficient means of screening family members.