Familial hypertrophic cardiomyopathy

Other Names: Cardiomyopathy familial hypertrophic; Heritable hypertrophic cardiomyopathy; Familial HCM

Familial hypertrophic cardiomyopathy (HCM) is an inherited heart condition characterized by thickening of the heart muscle. The thickening most often occurs in the muscle wall that separates the left and right ventricles from each other (interventricular septum). This may restrict the flow of oxygen-rich blood from the heart, or it may lead to less efficient pumping of blood.

Cause

Familial hypertrophic cardiomyopathy (HCM) is caused by mutations in any of several genes. The genes most commonly responsible are the MYH7, MYBPC3, TNNT2, and TNNI3 genes. Other genes that have not yet been identified may also be responsible for familial HCM.

The genes known to be responsible for familial HCM give the body instructions to make proteins that play important roles in contraction of the heart muscle. The proteins form structures in muscle cells called sarcomeres, which are needed for muscle contractions. Sarcomeres are made of protein fibers that attach to each other and release, allowing muscles to contract. The contractions of heart muscle are needed to pump blood to the rest of the body. While it is unclear exactly how mutations in these genes cause familial HCM, they are thought to lead to abnormal structure or function of sarcomeres, or reduce the amount of proteins made. When the function of sarcomeres is impaired, normal heart muscle contractions are disrupted.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

Familial hypertrophic cardiomyopathy (HCM) is inherited in an autosomal dominant manner. This means that having only one changed (mutated) copy of the responsible gene in each cell is enough to cause features of the condition. When a person with an autosomal dominant condition has children, each child has a 50% (1 in 2) chance to inherit the mutated copy of the gene.

In rare cases, a person with familial HCM has a mutation in both copies of the responsible gene, which leads to more severe signs and symptoms

Signs and symptoms

Signs and symptoms can vary. While some people have no symptoms, others may have chest pain, shortness of breath, palpitations, lightheadedness, dizziness, and/or fainting. Even in the absence of symptoms, familial HCM can have serious consequences such as life-threatening arrhythmias, heart failure, and an increased risk of sudden death.

Diagnosis

Familial hypertrophic cardiomyopathy (HCM) is caused by mutations in any of several known genes, and possibly other genes that have not yet been identified. Genetic testing for HCM is most informative as a "family test" rather than a test of one person. Results are most accurately interpreted after merging both genetic and medical test results from multiple family members. Ideally, the family member first having genetic testing should have a definitive diagnosis of HCM and be the most severely affected person in the family. Genetic testing of at-risk, asymptomatic relatives is possible when the responsible mutation has been identified in an affected family member. Testing should be performed in the context of formal genetic counseling. The fallowing tests are useful to diagnoise HCM

• Echocardiogram
• Electrocardiogram (ECG or EKG)
• Cardiac MRI

Treatment

The goal of hypertrophic cardiomyopathy treatment is to relieve symptoms and prevent sudden cardiac death in people at high risk.

They range from open-heart surgery to implantation of a device to control your heart rhythm.

• Septal myectomy.
• Septal ablation.
• Implantable cardioverter-defibrillator (ICD).

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition.

• Dehydrated alcohol (Brand name: Ablysinol) approved to induce controlled cardiac septal infarction to improve exercise capacity in adults with symptomatic hypertrophic obstructive cardiomyopathy who are not candidates for surgical myectomy.

NIH genetic and rare disease info

• NIH info on Familial hypertrophic cardiomyopathy

Familial hypertrophic cardiomyopathy is a rare disease.