Familial hypertrophic cardiomyopathy (HCM) is a genetic heart condition characterized by an abnormal thickening of the heart muscle, particularly the left ventricle. This thickening can impede the heart’s ability to pump blood effectively. The term “familial” signifies that this condition is inherited and tends to run in families. Familial HCM is considered the most common genetic heart disease, affecting an estimated 1 in 200 people globally.
Understanding Familial Hypertrophic Cardiomyopathy
Familial hypertrophic cardiomyopathy is an inherited disorder where the heart muscle, especially the left ventricle, thickens abnormally. This thickening, or hypertrophy, can make it difficult for the heart to fill with blood and pump it out efficiently. The abnormal muscle growth can also disrupt the heart’s electrical system, potentially leading to irregular heart rhythms.
The underlying cause of familial HCM is mutations in genes that produce proteins found in the heart muscle’s sarcomeres. These mutations are inherited in an autosomal dominant pattern, meaning one copy of the altered gene is sufficient to cause the disorder. The most commonly involved genes are MYH7 and MYBPC3, which together account for about 50% of familial HCM cases. Other genes, such as TNNT2 and TNNI3, are also associated with the condition. These genetic changes can lead to abnormal or reduced amounts of sarcomere proteins, impairing the heart muscle’s contraction and relaxation, even before significant thickening occurs.
Identifying the Signs
The symptoms of familial hypertrophic cardiomyopathy can vary significantly. Many affected people may experience no symptoms at all. However, some individuals may develop symptoms as the disease progresses or during physical exertion.
Common signs of familial HCM include shortness of breath, especially with physical activity, and chest pain. Palpitations, lightheadedness, dizziness, and fainting (syncope) can also occur due to the heart’s impaired ability to pump enough blood to the brain. A heart murmur may be detected during a physical examination. In some cases, the first indication of familial HCM might be a serious cardiac event, such as sudden cardiac death, particularly in young adults or athletes.
Diagnosis and Treatment Approaches
Diagnosing familial hypertrophic cardiomyopathy involves a comprehensive evaluation that begins with a medical history, including a family history of heart conditions. A physical examination may reveal a heart murmur or other signs of cardiac dysfunction. Several diagnostic tests are performed to confirm the diagnosis and assess the condition’s extent.
An echocardiogram, which uses sound waves to create images of the heart, is employed to visualize the heart muscle thickness and how well the heart’s chambers and valves are functioning. An electrocardiogram (ECG or EKG) measures the heart’s electrical activity and can show abnormalities related to muscle thickening. Cardiac MRI provides detailed images of the heart, allowing for the detection of thickening and scarring. Genetic testing can identify specific gene mutations linked to familial HCM, which is particularly useful given its inherited nature.
While there is no cure for familial HCM, treatment focuses on managing symptoms, preventing complications, and improving quality of life. Lifestyle modifications, such as avoiding strenuous exercise, are recommended. Medications are a primary treatment approach, with beta-blockers and calcium channel blockers commonly prescribed to help reduce the heart’s pumping strength and slow the heart rate. Other medications, such as mavacamten, may be used to reduce strain on the heart in obstructive cases.
For individuals at high risk of life-threatening arrhythmias, an implantable cardioverter-defibrillator (ICD) may be surgically placed to deliver electrical shocks to restore a normal heart rhythm. In cases where medication is insufficient, surgical procedures like septal myectomy, which removes part of the thickened heart muscle, or alcohol septal ablation, which uses alcohol to shrink the thickened tissue, may be considered to improve blood flow. Heart transplantation is a rare option for individuals with severe heart failure.
Family Considerations
A diagnosis of familial HCM has significant implications for close relatives. Genetic counseling is recommended for affected individuals and their family members to help them understand the inheritance patterns of the condition and their personal risk. This counseling provides information about the likelihood of passing the altered gene to future generations.
Cascade screening is a recommended approach to identify other family members who may have inherited the condition. This involves screening first-degree relatives of an affected person. These screenings include cardiac evaluations like echocardiograms and ECGs. If a specific gene mutation is identified, genetic testing can be offered to relatives. Regular follow-up is necessary for individuals diagnosed with familial HCM or those at risk to monitor for disease progression and adjust management strategies.