Patients at risk for a cardiomyopathy, Marfan syndrome, and Long QT syndrome are now being referred to the Center for screening, genetic testing and appropriate interventions. Identification of genetic markers is becoming increasingly important in both early diagnosis and treatment of many cardiac conditions. Indeed, many life-threatening arrhythmias are preventable, if family members are aware of their risk.
Genetic conditions of the cardiac system vary in their clinical presentations. There are diseases of the heart muscle (cardiomyopathies), diseases of heart rhythm (cardiac conduction defects), and abnormalities of the metabolism of certain blood proteins that cause an increased likelihood of developing atherosclerosis and coronary artery disease (dyslipoproteinemias). Some of these conditions have known genetic, and therefore hereditary, components and a family history of one of these conditions can increase your chances of developing that disease.
When Should I Suspect A Cardiovascular Condition May Be Hereditary?
If you have a personal or family history of any of the following, a genetic consultation may be appropriate for you:
- An enlarged heart
- Young or sudden deaths
- SIDS (sudden infant death syndrome)
- Fast heart rate or palpitations
- Fainting episodes or dizziness
- Heart failure
- Heart transplant, pacemaker, or defibrillator
- History of strokes
- Irregular heartbeat
- Very high cholesterol
- Muscle or skeletal disorder
- Genetic condition
What are the most common cardiac hereditary conditions?
Cardiomyopathies are diseases of the heart muscle (myocardium) associated with cardiac dysfunction. There are at least three types of cardiomyopathies: dilated cardiomyopathies (DCM), hypertrophic cardiomyopathy (HCM), and arrhythmogenic right ventricular cardiomyopathy (ARVC).
Dilated cardiomyopathy is a disease of the heart muscle characterized by dilation (stretching) and impaired contraction of the left or both ventricles of the heart. It can result in progressive heart failure and sudden cardiac death from ventricular arrhythmia. The prevalence of DCM in the general population is 40-50 cases per 100,000 individuals. The clinical presentation of DCM can range from strokes due to blood clots that break loose (thromboembolism), heart beat abnormalities (arrhythmias), progressive heart failure and to sudden death without warning symptoms. Approximately 35-50% of idiopathic (unknown cause) DCM may have a genetic cause. Other causes of DCM can be inadequate circulation of blood to the heart (ischemia), hypertension, metabolic deficiencies, immunologic abnormalities, infections, toxins, drugs, heart inflammation (myocarditis), and heart valve disease.
Hypertrophic cardiomyopathy is characterized by overgrowth of the left ventricle (left ventricular hypertrophy) that is usually asymmetric and can affect various regions of the ventricle. The prevalence of HCM might be as high as 1 case per 500 individuals in the general population. Symptoms are usually nonspecific, and may include breathlessness, chest pain, and fainting (syncope). The most serious complication of HCM is rapid movements of the ventricle that replace the normal ventricular contractions (ventricular fibrillation). The spectrum of disease ranges from very mild or even asymptomatic to debilitating. Approximately 50% of HCM is hereditary in nature.
Arrhythmogenic right ventricular cardiomyopathy
Arrhythmogenic right ventricular cardiomyopathy is characterized by progressive replacement of the right ventricle heart muscle with fat and fibers. The replacement of muscle with fat leads to an arrhythmia of the right ventricle, sustained ventricular fibrillation, and sudden death. The prevalence of ARDC is unknown, but about 30% of ARDC appears to be familial.
Cardiac conduction defects (Long QT syndrome)
Cardiac conduction defects are diseases of the heart’s rhythm. An example of a cardiac conduction defect is long QT syndrome. Long QT syndrome is an abnormality of the heart's electrical system. The problem is due to defects in the heart muscle cell structures, called ion channels, which control the flow of potassium and sodium in and out of the heart’s cells. These electrical defects predispose individuals to a very fast cardiac rhythm (tachyarrhythmia or tachycardia) called torsades de pointes which leads to fainting and may cause sudden cardiac death. Long QT syndrome may be acquired or inherited. The acquired form is more common and is usually caused by the administration of medications. Inherited long QT occurs in 1 in every 5,000-7,000 individuals.
Dyslipoproteinemias are a complex group of disorders that can cause elevated levels of low-density lipoproteins (LDLs) or triglycerides and decreased levels of high-density lipoproteins (HDLs) that can increase an individual’s susceptibility to coronary artery disease (CAD) and atherosclerosis. Increased levels of both LDL and HDL levels can be due to hereditary factors.
Is there a genetic test for hereditary coronary conditions?
Rare families are affected by a mutation in a single gene which cause hereditary coronary conditions. The family history and coronary conditions in a family are used to determine the likelihood of a hereditary coronary syndrome and, if a syndrome is suspected, which gene(s) should be analyzed.
It is generally most informative if a relative who has had coronary disease is tested first, to determine if an identifiable gene mutation exists in the family. If a mutation is identified in an affected relative, at-risk family members may elect to be tested for the familial mutation; those testing positive have a significantly increased risk of developing coronary disease, while those relatives testing negative may be told that they have the general population risk.
What should I do now?
Please use this section as background education. It is not a substitute for a clinical visit to our Center or discussion of a possible hereditary condition with your physician.
Make an appointment with your physician to discuss your risk of a hereditary coronary condition.
Make an appointment with the Center for Medical Genetics by calling 847.570.1029.
E-mail this page to a friend or loved one that may be at risk.