The Causes and Risk Factors Associated with Hypertrophic Cardiomyopathy (HCM)

• Shortness of breath, especially during exercise (ex: jogging, running, or climbing stairs)
• Light-headedness 
• Fainting or dizziness when standing up quickly 
• Passing out 
• Chest pain 
• Arrhythmias (abnormal heartbeats)
• Tiredness or fatigue 
• Palpitations (feeling of the heart beating too fast)

What Causes Hypertrophic Cardiomyopathy?

Genetics

Mutations can occur in one of several genes that encode for the cardiac sarcomere protein, which results in a wide variety of phenotypic expressions. The most commonly involved genes are MYH7, TNNI3, MYBPC3, and TNNT2. HCM is classified as an autosomal dominant disease as you can inherit it from your parents and may even pass it on to offspring. 

Depending on the gene defect (mutation), the type of disease can vary within a family or between family members. Some people that have a gene mutation for HCM may never develop symptoms. Further research is still needed to understand other factors/causes that increase the chance of developing this condition. 

Diagnosis

When diagnosing HCM, your doctor will take into account your medical history and a physical exam. There are also numerous tests that can be conducted to confirm HCM. The most common diagnostic test used is an echocardiogram,  which checks blood flow through the heart and the thickness of the heart muscles. Other diagnostic tests that are used include the following:

• Transesophageal echo (TEE)
• Genetic testing 
• Stress tests 
• Electrocardiogram (ECG)
• Holter and event monitors (used to detect any abnormal heart rhythms) 
• Cardiac magnetic resonance imaging (MRI)

It is essential to seek medical advice if you experience any symptoms, or have a family history as: "hypertrophic cardiomyopathy, when not diagnosed and not treated, carries a high incidence of sudden death," Dr. Philip Weintraub, a cardiologist at NYU Langone Health, explains to Survivornet. "So, therefore, one likes to make the diagnosis of a cardiomyopathy secondary to hypertrophic factors because there are things that could be done to prevent its progression and of course, prevent sudden death."

Hypertrophic Cardiomyopathy Risk Factors

HCM affects all age groups, genders, and ethnic backgrounds.  It is an inherited disease (passed down through families). If your parent has HCM, then you have a 50% chance of inheriting the same associated genetic mutation.  Dr. Weintraub added "I recommend genetic testing, especially in a young person who has hypertrophic cardiomyopathy". He explains this is necessary "because of the fact that the young person has family members that may not have symptoms and may be carrying the particular trait for HCM". 

While most people with HCM have a low risk for sudden cardiac death, there is still a need to identify the small percentage of people with HCM that have a higher risk of suffering from severe cardiac complications. People who have been diagnosed with HCM have a higher risk of sudden cardiac death if they: 

• Have severe symptoms and poor heart function 
• Have a family history of sudden cardiac death 
• Have a history of abnormal heart rhythms (arrhythmia) with a fast rate 
• Are young and have had several episodes of fainting (syncope)
• have an abnormal blood pressure response with exercise

Complications of HCM 

While complications are not very common, they can occur, especially if HCM is left undiagnosed, untreated, or not appropriately managed and treated. Some complications of HCM that can occur include the following: 

• Sudden cardiac death. As most people are not aware they have HCM, the most severe symptom that may present is sudden cardiac arrest. This is a rare complication, but it can occur in people of all ages and even seemingly healthy young people. 
• Fainting (syncope). This can be caused by a blockage of blood flow or an irregular heartbeat. Any unexplained fainting can potentially be associated with sudden cardiac arrest.
• Mitral valve disease. If blood flow leaving the heart is blocked by the thickened heart muscles, the valve found between the left ventricle and left atrium (mitral valve) may be unable to close effectively. This results in blood leaking backward into the left atrium (mitral valve regurgitation), which may make the symptoms of HCM worse. 
• Atrial fibrillation. Due to a thickened heart muscle, the structure of the heart cells change, and this can result in changes in the heart's electrical system – resulting in irregular or fast heartbeats. Atrial fibrillation can increase the risk of developing blood clots. 
• Blocked blood flow. In many people with HCM, who have thickened heart muscle, the blood is blocked from leaving the heart. This can cause chest pain, fainting spells, shortness of breath, and dizziness. 
• Dilated cardiomyopathy. In a small percentage of people with HCM, the thickened heart muscle becomes ineffective and weak, resulting in an enlarged (dilated) ventricle that pumps blood with less power. 
• Heart failure. The thickened heart muscle can, over a period of time, become stiff. If it becomes too stiff to fill the heart with blood, then the heart can no longer pump enough blood to meet the requirements of the body. 

Dr. Aeshita Dwivedi, a cardiologist at Lenox Hill Hospital in New York, simply explains it, "Heart failure is a condition where the muscle of the heart becomes weak. It can weaken in the sense that it doesn’t pump enough blood to the rest of the body, which can impact the organs of the body, like the kidneys liver, as well as your lungs, when it exists for a prolonged period of time."

Moving Forward – Questions to Ask Your Doctor: 

• What are my chances of having HCM if one of my grandparents has it? 
• Do I have any risk factors if I do not experience any symptoms associated with HCM? 
• I am young and have HCM. Do I have a high risk of sudden cardiac death? 
• Are there any complications associated with HCM? 

Learn more about SurvivorNet's rigorous medical review process.