Hypertrophic cardiomyopathy is an inherited disorder in which the heart muscle becomes hypertrophied, or grows thicker than it should be. It occurs in about 1 in 500 adults. Though many people with hypertrophic cardiomyopathy lead normal lives with few limitations, there is the potential for developing severe symptoms and serious heart-related complications, including heart failure, arrhythmia, and even sudden cardiac death.

The heart is made up of four chambers—two upper atria and two lower ventricles—that work together to pump blood to the body. The heart’s left ventricle receives oxygen-rich blood from the left atrium. When the left ventricle’s muscular wall contracts, blood is pumped into the aorta, the largest blood vessel in the body, and onward to the rest of the body.

In people with hypertrophic cardiomyopathy, the wall of the left ventricle contracts very strongly and becomes thicker than usual. The increased thickness can occur in any part of the left ventricle, but is often present in the ventricular septum, the part of the heart that divides the two ventricles.

The heart contracting very strongly and thickening can have several negative consequences. For one, the ventricle may not pump blood efficiently, leading to heart failure. In some cases, the thickening of the septum may actually obstruct the flow of blood out of the ventricle, a condition known as obstructive hypertrophic cardiomyopathy. The impairment of blood flowing out of the heart can produce severe symptoms, including shortness of breath, chest pain, and loss of consciousness. In many cases of obstructive hypertrophic cardiomyopathy, the mitral valve, which regulates blood flow into the left ventricle, does not close properly, resulting in blood leaking backwards into the left atrium. The changes that occur in the heart due to hypertrophic cardiomyopathy can also increase the risk of several different types of cardiac arrhythmias.

In some patients with hypertrophic cardiomyopathy, the changes in the heart directly relate to variations in one of several genes that regulate heart function and structure. These genetic variations can be passed from parents to their children, and often lead to multiple cases of hypertrophic cardiomyopathy within families. If a parent has a gene variant that causes hypertrophic cardiomyopathy, there is a 50% chance that it will be passed to a child. However, among those who inherit gene variants associated with hypertrophic cardiomyopathy, not all will develop the condition, and among those that do, there can be different levels of severity.

However, in the majority of patients with hypertrophic cardiomyopathy, the cause is less clear and cannot be attributed to a single gene variant. In these cases, multiple gene variants and/or environmental conditions may be contributing.

Because of the inherited basis of hypertrophic cardiomyopathy, genetic testing may be recommended for the parents, siblings, and children of those diagnosed with the condition.

Many people with hypertrophic cardiomyopathy don’t have any symptoms. When symptoms are present, they can include:

• Chest pain
• Shortness of breath (especially with physical exertion)
• Lightheadedness
• Fainting
• Heart palpitations
• Fatigue
  

Complications of hypertrophic cardiomyopathy may include:

• Heart failure (often characterized by shortness of breath and fluid retention)
• Heart arrhythmias, including atrial fibrillation and ventricular tachyarrhythmias
• Stroke
• Sudden cardiac death

To diagnose hypertrophic cardiomyopathy, your doctor will review your medical history, perform a physical exam, and order one or more diagnostic tests.

Your doctor will begin by asking you about your symptoms and whether other people in your family have hypertrophic cardiomyopathy. During the physical exam, your doctor will check your pulse and use a stethoscope to listen to your heart. People with hypertrophic cardiomyopathy may have a heart murmur or other abnormal heart sounds.

Additional tests are necessary to confirm the diagnosis of hypertrophic cardiomyopathy and to rule out other heart conditions. These may include:

• Electrocardiography (ECG or EKG), a test that measures the electrical activity of the heart. Around 95% of people with hypertrophic cardiomyopathy have abnormal ECG readings.
• Echocardiography, an imaging test that uses high-frequency sound waves (ultrasound) to produce an image of the heart. This test allows doctors to measure the thickness of the heart muscle and visualize the rest of the heart as it beats. This test is also useful to determine if blood flow out of the heart is obstructed.
• Cardiac magnetic resonance (CMR) imaging, a test that creates an image of the heart using magnetic fields. This test may be used to assess the structure and function of the heart and look for scarring or other abnormalities in the heart muscle.
• Ambulatory ECG, a test in which you wear an ECG monitoring device for an extended period. For instance, a Holter monitor is typically used to measure and log a patient’s ECG over a 24-to-48-hour period. The test helps detect abnormal heart rhythms.
• Exercise stress testing, a test in which you exercise on a treadmill or exercise bike while connected to ECG, heart rate, and blood pressure monitors, and sometimes echocardiography equipment.
• Transesophageal echocardiography, a test in which a thin tube equipped with an ultrasound transducer is guided down the throat. The transducer produces images of the heart and can be useful to assess the heart valves.
• Cardiac catheterization, a test in which a doctor inserts a catheter—a long, thin tube— into an artery in the groin or arm and guides it to the heart. Once in place, the catheter can be used to image the coronary arteries supplying blood to heart and measure pressures in the heart’s chambers; it can also determine if a blood flow obstruction is present.

While there is no cure for hypertrophic cardiomyopathy, many treatments are available that can reduce symptoms and lower the risk of complications. These may include:

Lifestyle changes. For most people with hypertrophic cardiomyopathy, physical activity is encouraged. There may be increased risks associated with certain types of activities, such as high-intensity exercise and competitive sports. For this reason, people with hypertrophic cardiomyopathy should talk to their doctor about the kinds of physical activities in which they can safely participate.

Medications. Various medications may be recommended to relieve symptoms and/or reduce risks, including:

• Beta-blockers to reduce chest pain and shortness of breath. They work by slowing down your heart rate and reducing the force of heart muscle contractions.
• Calcium blockers to reduce chest pain and shortness of breath. They work similarly to beta-blockers and are sometimes used in combination with them.
• Anti-arrhythmic drugs to treat heart arrhythmias.
• Diuretics to reduce fluid retention and treat symptoms related to heart failure.
• Mavacamten and other sarcomere inhibitors, new medications that can reduce the strength of heart muscle contractions. They are used to treat people with obstructive hypertrophic cardiomyopathy.
• Blood thinners to protect against stroke

Devices. Implantable cardioverter-defibrillators (ICDs) are used to treat people with hypertrophic cardiomyopathy who have dangerous heart arrhythmias. An ICD is a device that can detect dangerous arrhythmias and, in response, send an electrical impulse to the heart to restore a normal rhythm. ICD implantation is done using a minimally invasive surgical procedure.

Septal reduction therapy. If symptoms from obstructive hypertrophic cardiomyopathy don’t improve with medications, there are procedures that reduce the thickness of the ventricular septum, which can improve blood flow from the heart to the rest of the body.

• Septal myectomy. This involves the surgical removal of tissue from the ventricular septum to relieve the obstruction.
• Alcohol septal ablation. In this procedure, a catheter is used to inject ethanol into the vessel that delivers blood to the thickened portion of the ventricular septum. The ethanol—a type of alcohol—causes the cells that make up the thickened muscle to die. This relieves the obstruction by reducing the contractility and thickness of the affected tissue.

The outlook for most people with hypertrophic cardiomyopathy is good. Many people experience few, or even no, symptoms and have a normal life expectancy. Some people with the condition, however, may develop complications such as heart failure and potentially dangerous arrhythmias, which is why early diagnosis and treatment are essential.

“The Yale Hypertrophic Cardiomyopathy Program is a regional center that provides comprehensive, expert care for patients with hypertrophic cardiomyopathy,” says John Stendahl, MD, PhD, a Yale Medicine specialist in inherited and infiltrative cardiomyopathies and co-director of Yale’s Hypertrophic Cardiomyopathy Program. “Patients in our program have access to a specialized team of physicians and other providers with expertise in hypertrophic cardiomyopathy, including specific fields such as cardiac imaging, cardiac arrhythmias, genetics, interventional cardiology, cardiac surgery, and heart failure and transplantation. We offer state-of-the-art diagnostic testing and therapeutics, including treatment with the new myosin inhibitor therapies, such as mavacamten. As an academic center, the Yale program is also conducting cutting-edge research in the field of hypertrophic cardiomyopathy. This research helps to advance our understanding of hypertrophic cardiomyopathy and develop new treatments.” Adds Nikhil Sikand, MD, another Yale Medicine specialist in inherited and infiltrative cardiomyopathies,“We believe that the benefits of this research pass directly to our patients. We have active programs in both basic and clinical research, and offer patients opportunities to participate in clinical trials of the latest treatments.”