HCM is the most common inherited cardiomyopathy (disease of the heart muscle). It affects as many as 1 in 500 people in the United States. While HCM does not always have a significant impact on day-to-day life, it is a serious disease. It has many potential complications that can greatly affect quality of life and life expectancy.
HCM is a genetic disease caused by inherited gene mutations that cause the muscles of the left ventricle to become thickened (left ventricular hypertrophy). HCM can prevent the heart from pumping properly by reducing the size of the inside of the left ventricle and obstructing the normal flow of oxygen-rich blood from the heart to the rest of the body. HCM is a progressive disease that can result in serious complications over time.
Symptoms of HCM can include:
Symptoms often only appear during exercise or strenuous physical activity. Some people with mild HCM may not experience any significant symptoms, while people with severe HCM may experience symptoms even while resting.
Complications are medical conditions caused by another disease. HCM can cause many complications, including:
These complications can cause the severe symptoms sometimes seen in HCM.
Arrhythmias, abnormal heart rhythms, are a common complication of HCM. There are several types of arrhythmia that affect heart rate and heart function. Atrial fibrillation, also called AFib, is the most common arrhythmia experienced by people with HCM.
AFib causes disorganized and unsynchronized contractions of the atria, the smaller chambers of the heart that help fill the ventricles. This can cause symptoms such as heart palpitations, irregular heartbeat, shortness of breath, lightheadedness, fatigue, and chest pain. AFib can also cause dangerous blood clots, which can lead to stroke. Medications can control AFib, and blood thinners (anticoagulants) can help prevent blood clots from forming.
Rarely, HCM may cause dangerous ventricular arrhythmias that require treatment. Rapid heartbeats faster than 100 beats per minute (ventricular tachycardia) for longer than 30 seconds at a time can be a sign of an increased risk of sudden death. Contact your doctor immediately if you experience this issue. Your doctor may recommend a change in medication or the placement of an implanted cardioverter defibrillator.
HCM can affect the heart’s mitral valve, which allows blood to flow from the left atrium into the left ventricle while preventing blood from flowing backward into the atrium when the ventricle contracts. HCM can cause abnormalities in the mitral valve that allow blood to leak, or regurgitate, backward into the left atrium.
Mitral valve disease can cause a heart murmur without any symptoms, or it can cause fatigue, shortness of breath, and irregular heartbeat. Severe disease may need to be treated with surgery or heart valve replacement.
Infective endocarditis (IE) is an infection inside the heart, usually of the heart valves. HCM affects the mitral valve, putting people with HCM at higher risk of IE of the mitral valve.
IE can occur when there is damage to the tissue that covers the heart valves, making it prone to infection if bacteria are present in the bloodstream. IE can cause fever and other symptoms of infection, as well as chest pain, shortness of breath, and other symptoms caused by mitral valve dysfunction.
Intravenous antibiotics can treat IE. If damage to the mitral valve is severe, surgery may be necessary to repair or replace it. Prophylactic (preventive) antibiotics can help prevent IE, such as taking antibiotics before dental procedures that can introduce bacteria into the bloodstream.
Rarely, HCM can lead to heart failure, a condition that occurs when damage to the heart makes it unable to provide oxygen-rich blood to the body. Heart failure can cause fatigue, shortness of breath, difficulty breathing, arrhythmia, persistent cough, fluid retention in the lower limbs, and other symptoms.
Heart failure can be deadly, but it can often be managed by medication, surgery, or an implantable cardioverter defibrillator. Some cases may require a heart transplant.
Some people with HCM have a degree of obstruction to blood flow out of the heart and into the aorta, which carries oxygen-rich blood to the rest of the body. This outflow obstruction happens when the septum (wall) between the left and right ventricles becomes thickened, causing symptoms including chest pain, dizziness, fainting, and shortness of breath with exertion.
Obstructive HCM symptoms can be treated with medication, but surgery to reduce the thickness of the septum — surgical septal myectomy — is sometimes needed. A newer procedure called nonsurgical septal myectomy uses an alcohol infusion into one of the coronary arteries. This causes the death of some of the overgrown septum tissue (sometimes called “a controlled heart attack” or “ethanol ablation”). This procedure has also been shown to be effective in reducing the obstruction to blood flow.
Sudden cardiac death (SCD), also called sudden cardiac arrest, rarely occurs with HCM. However, some people with HCM are at higher risk. SCD can occur in young people — usually athletes — or in adults. Even if HCM is not causing any noticeable symptoms, it can increase the risk of SCD.
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HCM varies widely in how it affects individuals. Studies have shown that people diagnosed with HCM have a high survival rate — a one-year survival rate of 98 percent and a 10-year survival rate of 75 percent.
In fact, many people with HCM never develop any symptoms, and it is believed that many people with HCM are never diagnosed. Research suggests that most people with HCM have a normal life expectancy regardless of when HCM is diagnosed.
However, certain individuals are at a much greater risk of death due to the many possible complications of HCM. Risk factors for sudden cardiac death due to HCM include a family history of sudden death, a history of syncope (fainting), and moderately severe obstruction on diagnostic tests.
In addition to the risk factors for sudden death, an increased risk of heart-related death is also associated with a life-threatening arrhythmia called nonsustained ventricular tachycardia and with moderate to severe functional impairment from heart failure.
HCM affects many people in many different ways. Learning about all the ways a chronic condition can affect your life can feel overwhelming, if not a little scary. However, HCM is a very treatable disease, and many of its complications are treatable too. Knowing more about HCM can encourage you to seek medical help to prevent negative outcomes.
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