Obstructive hypertrophic cardiomyopathy (NORD)

Obstructive hypertrophic cardiomyopathy is a genetic disorder where the walls of the heart become thicker, or hypertrophied.

While it might seem a thicker heart is a good thing, the larger muscles prevent the ventricles—the two lower chambers of heart—from fully relaxing between contractions.

In addition, the walls of the heart are stiffer and less compliant, so they can’t stretch out as much. This reduces the amount of blood that gets into the heart, lowering the cardiac output, or the amount of blood pumped out of the heart per minute.

Usually, the left ventricle is more affected, and in most cases, muscle growth is asymmetrical, meaning that the wall between the two ventricles, called the septum, grows larger relative to the free wall.

In some people, the thickened septum can obstruct the outflow of blood from the left ventricle, which is why hypertrophic cardiomyopathy is sometimes called obstructive hypertrophic cardiomyopathy.

In these cases, the blood that comes out of the left ventricle is forced through a smaller opening, which creates a “pulling” effect on the nearby mitral valve that further obstructs the outflow of blood.

Most cases of obstructive hypertrophic cardiomyopathy are familial. This means the condition is inherited from a parent.

Inheritance is autosomal dominant, meaning only a single copy of a disease-causing gene variant is needed to cause the disease.

Variants in many different genes that code for proteins found in heart muscle, such as myosin and troponin T. can cause obstructive hypertrophic cardiomyopathy.Symptoms of obstructive hypertrophic cardiomyopathy can begin at any age, but they most often start in early adulthood.

Over time, the heart becomes unable to do its job effectively, leading to signs of heart failure such as excessive tiredness and shortness of breath, especially during exercise.

Because there is less blood coming out of the heart, the amount of blood transported to the brain can decrease. This may cause fainting.

Individuals are also more prone to developing arrythmias, or irregular heart rhythms, which can sometimes be life-threatening.

Of note, obstructive hypertrophic cardiomyopathy is the most common cause of sudden cardiac death in young individuals, especially young athletes.Diagnosis is considered based on assessment of the patient’s symptoms and family history.

Clinically, individuals with obstructive hypertrophic cardiomyopathy will have a heart murmur, which is a whooshing sound made by rapid, turbulent blood flow through the heart.

Diagnosis is confirmed with an echocardiogram, which will show the thickened ventricular walls and decreased cardiac filling.

In some individuals, a stress test may be performed along with an echocardiogram to measure exercise capacity and obstruction of blood flow during exertion.

Genetic testing can be helpful for making a diagnosis; however, it may not always be possible to identify the disease-causing variants.There is currently no cure for obstructive hypertrophic cardiomyopathy, and treatment focuses on managing the symptoms.

In mild cases, treatment may include medications that slow down the heart rate, which gives the ventricles more time to fill between contractions.

Individuals with more severe symptoms may benefit from a novel treatment called mavacamten, which targets the underlying cause of the disease.

It acts by allowing the heart muscle to relax and use energy more efficiently. In addition to pharmacological treatment, some people may need to undergo surgery to remove the thickened part of the septum.

Finally, because of the risk of sudden cardiac death, people diagnosed with obstructive hypertrophic cardiomyopathy are often recommended to stop high-intensity activities.

They may also be offered an implantable defibrillator, which is a device that monitors the heart rate and delivers a shock when it detects an irregular heart rhythm to make the heart beat normally again.

As a quick recap, obstructive hypertrophic cardiomyopathy is a genetic disorder affecting the heart muscle where the walls of the heart and the septum between the right and left ventricles become thickened, obstructing blood flow out of the heart.

Eventually this causes signs of heart failure, such as fatigue, shortness of breath, and fainting. Affected individuals are more prone to arrhythmias and sudden cardiac death.

Diagnosis is based on the findings of an echocardiogram and management focuses on improving the symptoms. Because of the risk of sudden death, individuals may be advised to cease any high-intensity activities and be