Genes, genetic testing and heart conditions

Information and resources for consumers

Inherited heart conditions are a group of conditions that affect the heart and can be passed on through families.

Types of inherited heart conditions

There are several types of inherited heart conditions including inherited cardiomyopathies, abnormal heart rhythms and other conditions.

Cardiomyopathies are diseases of the heart muscle affecting its function, size or shape. Some cardiomyopathies are inherited including:

• hypertrophic cardiomyopathy – is a condition in which the heart muscle becomes abnormally thick. The thickened heart muscle can make it harder for the heart to take in and pump out blood with each heartbeat. It is the most common form of inherited heart condition, affecting one in every 200 Australians.
• arrhythmogenic cardiomyopathy – is a rare condition that affects the heart’s structure where the walls of the heart become weak. It can affect the electrical system of the heart and the heart’s ability to pump blood.
• familial dilated cardiomyopathy – is a disease that causes the muscle wall to stretch and become thin. The muscle walls become enlarged and weakened which makes it harder for the heart to pump blood to the rest of the body.
• familial restrictive cardiomyopathy – is a condition in which the walls of the lower chambers of the heart become stiff. As a result, the heart can’t expand and fill with blood properly between heartbeats.

• and other familial cardiomyopathies.

Abnormal heart rhythms are caused by a fault in the heart’s electrical system that controls its pumping rhythm. Some heart rhythm disorders are inherited including:

• Brugada syndrome – is a rare condition that affects the heart’s electrical system. It can cause fast, irregular heartbeats which can lead to fainting or, in serious cases, a cardiac arrest when the heart stops beating.
• catecholaminergic polymorphic ventricular tachycardia – is a rare disorder that can cause irregular and fast heartbeats. It usually happens when a person is under physical or emotional stress.
• long QT syndrome – is a disorder that affects the heart’s electrical system. It can cause fast or irregular heartbeats, fainting or seizures. It may also cause cardiac arrest in some people.
• and other inherited abnormal heart rhythms.

Other inherited conditions and gene variants that may impact the heart and blood vessels include:

• congenital heart disease - is a collective term for problems with the heart’s structure that are present from birth. They can affect blood flow to the heart and the rest of the body.
• familial hypercholesterolemia – is an inherited condition that affects the way the body processes cholesterol. People with familial hypercholesterolemia have a higher risk of heart disease and early heart attack.
• Marfan syndrome – is an inherited disorder that affects the connective tissue. Faulty connective tissue can weaken the aorta — the large artery that arises from the heart and supplies blood to the body. The syndrome can also affect the heart valves.
• sudden arrhythmic death syndrome (SADS) – occurs when a person dies suddenly from a cardiac arrest with no known obvious cause. It can affect people under 50 years of age who are fit and healthy. A range of inherited heart conditions can cause SADS.
• hereditary amyloidosis – is a rare disease, causing abnormal deposits and build-up of proteins in the body. Some genes variants can lead to amyloid deposits in the heart.

Symptoms of inherited heart conditions

Some people with inherited heart conditions do not experience any symptoms, while others may have symptoms such as:

• dizziness or light-headedness
• fainting or blackouts
• palpitations (a feeling of your heart racing, thumping, fluttering, pounding or skipping beats)
• shortness of breath.

Sadly, some families only become aware of an inherited heart condition when a family member dies suddenly without an obvious cause. A range of inherited heart conditions can cause sudden death and therefore, it is important to investigate family members following such an event.

Causes of inherited heart conditions

Your body is made up of trillions of cells. Each cell contains information that makes you unique. This information is contained in your genes (sometimes referred to as your DNA or your chromosomes). We each have between 20,000 and 25,000 genes that we inherit from our parents.

Inherited heart conditions are caused by a change in one or more genes. If one of your parents has a specific gene, there’s a chance you could inherit it. It means there’s also a chance you could pass it on to your children.

Symptoms of an inherited heart condition can appear at any age, meaning some people might not be diagnosed until adulthood. You can also pass the gene on to your children without knowing if, or how, it might affect them.

Diagnosing inherited heart conditions

If your doctor suspects you might have an inherited heart condition, they will ask you about your symptoms, and your personal and family history of heart disease. They will also check your blood pressure, pulse and will listen to your heart.

Your doctor may also arrange for one or more of the following tests:

• electrocardiogram (ECG) – records a detailed snapshot of your heart rate and rhythm. You may have this done while you are resting or exercising (for example, on a treadmill).
• echocardiogram – gives a picture of your heart using ultrasound. It helps your doctor check your heart’s valves, chambers, and heart muscle.
• magnetic resonance imaging (MRI) – creates detailed images of your heart. This test shows your doctor the structure of your heart and how well it is working.
• computed tomography (CT) scan of the heart - creates 3D images of the heart and its blood vessels
• electrophysiology studies – examines the heart’s electrical activity. This test helps your doctor to work out the type and cause of an abnormal heart rhythm.

Family history and genetic testing

With your doctor or health professional, it is important to draw a medical family tree. This can help to “paint a picture” to see if you have - or have had - any other family members with the same condition.

Your doctor may also recommend genetic testing to:

• confirm the diagnosis of an inherited heart condition
• assess whether you have the same gene variant as an affected family member.

Genetic testing typically involves taking a blood sample or cheek swab.

Genetic counselling is an important part of genetic testing. It helps to ensure that you understand the process and potential risks, limitations and uncertainties of getting tested. After you’ve had a genetic test, genetic counselling helps you to understand the condition and potential impacts of the results on your health and the health of your family members.

Limitations of genetic testing

• Having a gene variant doesn’t mean that you’ll definitely develop a heart condition. It also doesn’t tell you when or how you will be affected by the gene variant.

• People with the same gene variant can be affected in different ways.

• It’s important to remember that genetic testing may not identify all possible gene variants that could cause health problems in the future.

Knowing that you carry a gene variant allows your doctor to closely monitor you for any signs of the heart condition. Speak to your doctor or contact a clinical genetic service near you for more information about genetic testing.

Treatment for inherited heart conditions

Depending on the type of inherited heart condition you have, there are several treatment options that can help you manage your condition including:

• taking prescribed medicines

• implantable devices such as an implantable cardioverter defibrillator (ICD) or pacemaker

• surgery to repair or replace damaged valves, blood vessels or other parts of your heart.

What research is the Heart Foundation funding on genes and inherited heart conditions?

The Heart Foundation is funding research to enhance our understanding, diagnosis and management of inherited heart conditions.

Dr Paul Lacaze is studying how protective gene variants reduce the risk of heart disease among healthy older adults. Read more, here.

Professor Diane Fatkin is investigating how genes play a role in influencing a person’s risk of developing atrial fibrillation (a type of abnormal heart rhythm) and response to treatment. Watch an interview with Professor Diane Fatkin explaining her research, here.

Dr Sonia Shah is exploring the use of genomic data (data from the study of genes and their structure, function and expression) to improve the understanding, prevention and management of heart disease. Read more, here.