What is Hypertrophic Cardiomyopathy?
Hypertrophic cardiomyopathy (HCM) is a disease in which the heart muscle becomes abnormally thick due to a disorganized layout of heart cells. The thickened heart muscle can make it harder for the heart to function, and lead to many types of symptoms.
It is estimated that approximately 0.2% of people worldwide have HCM, making it one of the more common genetic diseases. It is predominantly a genetic disease, with approximately 40% of cases linked to known genetic mutations passed on by one’s parents. If a parent has the condition, there is a 50% chance of passing it on to each child. Because of this high risk of transmission, family members of people with HCM are recommended to be screened routinely.
HCM can be either obstructive (2/3 of people) or non-obstructive. In obstructive HCM, the wall (septum) between the two bottom chambers of the heart is thick, which may block the flow of blood from the left ventricle to the aorta. In non-obstructive HCM, the heart’s main pumping chamber still becomes stiff but blood outflow is not blocked.
HCM often is not diagnosed, or diagnosed late in life because many of the changes that occur in the heart can occur late in life, or people with the disease may have few, if any, symptoms. In other people, they can occur early in life, either because of early symptoms or changes on diagnostic tests.
Symptoms caused by HCM include:
- Shortness of breath
- Chest pain
- Rapidly beating heart (palpitations) due to heart rhythm abnormalities (arrhythmias)
- Lightheadedness or fainting (syncope)
- Heart failure
- Sudden cardiac death (in less than 1% of people with HCM)
How is HCM Diagnosed?
HCM is diagnosed with a combination of physical assessment, cardiac imaging tests, stress tests and genetic blood tests. If you are referred to the LHSC HCM Program, you will be seen by one of three cardiologists specialized in HCM. You may also be seen by a genetic counsellor. If you have suspected HCM, you may also be asked to perform one or more of the following tests to aid in the diagnosis:
- Transthoracic echocardiogram
- Exercise stress test
- Holter monitor
- Cardiac MRI
- Transesophageal echocardiogram
- Cardiac catheterization or angiography
- Bloodwork, including genetic testing
How is HCM Treated?
Following an assessment by the HCM team, a treatment plan will be recommended based on the test results and your symptoms. Usually, this involves medications to help resolve the outflow obstruction, arrhythmia or heart failure. You will likely receive recommendations on lifestyle changes if any are required.
In rare circumstances, if the risk of life-threatening arrhythmias is high, it may be recommended that you receive an implanted cardiac defibrillator (ICD).
In rare cases of severe obstruction not treated sufficiently with medications, it may be recommended that you have surgery (septal myectomy) or a non-surgical intervention (septal ablation) to relieve the obstruction mechanically.