Cardiac Genetics

At First Light Genetics we specialise in helping individuals and families with cardiac (heart) conditions that have a genetic basis. Our consultant clinical geneticist, Dr Mohammad, is highly trained and experienced in a range of cardiac genetic conditions.

Our Darlinghurst clinic focuses on genetic heart diseases. We can arrange genetic testing for all kinds of cardiomyopathy (conditions that affect the heart muscle) and heart arrhythmias (irregular heartbeat).

To find out if a person’s heart condition has a genetic basis, we will first:

  • Look at their signs and symptoms
  • Review the pictures that were taken of their heart (cardiac imaging; echocardiogram and or cardiac MRI)
  • Take a detailed medical and family history

If these suggest there may be a genetic basis for the heart condition, we will talk about the different types of genetic testing, including possible outcomes. We will then arrange suitable genetic testing.
If a genetic cause is found, we will explain the diagnosis and its possible impact on the individual and related family members. We will then work with the patient’s cardiologist to develop an individual treatment plan.


Cardiomyopathy is a condition affecting the function, size, or shape of heart muscle. In many people, cardiomyopathy is caused by a genetic change that was inherited (passed down) from a parent.

There are several different types of cardiomyopathy. All cardiomyopathies affect the way the heart pumps blood through the body.

  • Dilated cardiomyopathy (DCM) is the most common type of cardiomyopathy, and is caused by an inherited genetic change in up to 4 out of 10 people with the condition. In people with this type of cardiomyopathy, part of the heart, the left ventricle, is enlarged (dilated).
  • Hypertrophic cardiomyopathy (HCM) is the most common inherited heart condition, and is thought to affect as many as 1 in 200 Australians. In hypertrophic cardiomyopathy, the walls of the heart are thicker than usual.
  • Arrhythmogenic right ventricular cardiomyopathy (ARVC) (also known as Arrhythmogenic Right Ventricular Dysplasia [ARVD]) is an inherited cardiomyopathy that usually appears in adulthood. The muscle in the lower right chamber of the heart (right ventricle) is replaced by fat tissue. Over time, this interferes with the way the heart pumps blood. It can also cause an irregular heartbeat.
  • Left ventricular noncompaction cardiomyopathy is a very rare inherited cardiomyopathy. Tiny rod-like structures (trabecula) that increase in size and number over time develop in the heart muscle early in life. These trabeculae interfere with the way the heart functions.
  • Restrictive cardiomyopathy is the most rare form of cardiomyopathy. The lower chambers of the heart (ventricles) become very stiff and inflexible, which stops them expanding as they fill with blood.

You can find out more about genetic testing and the different types of cardiomyopathy here.

Heart Arrhythmias

A heart arrhythmia is an irregular heartbeat. Our heartbeat is controlled by electrical signals in the heart. Arrhythmias can occur when there are problems with these electrical signals.

An arrhythmia can cause the heart to beat too fast, too slow, or out of rhythm, which means blood may not be pumped around the body properly. Depending on how much the blood flow is affected, arrhythmias may be harmless or life-threatening.

There are several types of arrhythmias. Many things can cause an arrhythmia to develop, such as a virus, alcohol, caffeine, exercise, medicines, or recreational drugs.

In some people, arrhythmias are caused by a change in their genetic makeup. This may be inherited (passed down) from one or both of their parents or it may be a new change. Genetic arrhythmias are rare but they can cause serious health effects. The main types of genetic arrhythmias are:

  • Long QT syndrome. People with long QT syndrome have a particular change in the pattern of electrical activity in the lower chambers of their heart (ventricles). These changes affect the heartbeat and can be seen on a test called an electrocardiogram. This can cause very serious arrhythmias, which often start when during childhood.
  • Brugada syndrome. Like Long QT syndrome, Brugada syndrome affects the electrical activity in the ventricles. The symptoms may be brought on by a fever or certain types of medications.
  • Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT). During an episode of CPVT, changes in electrical activity in the ventricles cause extra heartbeats. The first signs of CPVT are usually seen in childhood during intense physical activity or times of high emotions.
  • Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) (also known as Arrhythmogenic Right Ventricular Dysplasia [ARVD]). In people with ARVC, the muscle in the right ventricle is replaced by fat tissue. This can cause an irregular heartbeat.
  • Short QT syndrome. People with short QT syndrome have a particular change in the pattern of electrical activity in the heart. This change can be seen on an electrocardiogram. It can affect the ventricles or upper chambers (atria) of the heart.
  • Wolff-Parkinson White (WPW) syndrome. People with WPW syndrome have periods where their heartbeat is unusually fast (more than 100 beats every minute). This is caused by an extra electrical signalling pathway between the upper and lower chambers of the heart.

Connective tissue diseases affecting the heart and blood vessels

Connective tissue holds the different parts of the body together. There are several diseases of the connective tissue, and some can be caused by genetic changes. Connective tissues diseases that affect the heart include:

  • Marfan syndrome. Symptoms of Marfan syndrome are often first seen during early childhood, and may affect the heart, eyes, blood vessels, and skeleton. In some people, the walls of the aorta (main blood vessel taking blood away from the heart) are weakened and the aorta becomes much larger than usual. This can cause a bulge or a tear in this critical blood vessel.
  • Loeys-Dietz syndrome. This condition can affect many parts of the body, including the heart and blood vessels, skin, eyes, bones, muscles, and skull. Sometimes the aorta becomes enlarged, which can cause a bulge or tear.
  • Vascular Ehlers-Danlos syndromes (vEDS). This is a rare condition that affects internal organs and blood vessels. In some people, blood vessels and internal organs may split, which can be life threatening.
  • Classical Ehlers-Danlos syndromes (cEDS). This condition mostly affects the skin and joints. People with cEDS may have fragile skin that splits easily, thin scars, and wounds that take longer than usual to heal. They may also have joints that move more than usual (hypermobility) or separate (dislocate).

Familial Hypercholesterolaemia

People with hypercholesterolaemia have much higher levels of a particular type of fat (low-density lipoprotein, or LDL) than usual. The LDLs may stick to the sides of the arteries, making them hard and narrow. If too much LDL builds up, it can cause a heart attack.

In people with familial hypercholesterolaemia (FH), high LDL levels are caused by a genetic change that was inherited from one or both parents. This genetic change interferes with the way the body removes LDL cholesterol from the blood.

Around 1 in 250 people have FH. Early diagnosis and treatment of FH reduces the likelihood of having a heart attack.

Frequently asked questions

The results of cardiac genetic testing can show whether a person has an inherited or new change in a gene that can lead to a heart problem.

Usually either a blood sample or a cheek swab (light scrape of the skin inside the cheek) is taken.

If you or your family have a history of heart conditions at a young age, your cardiologist may recommend genetic testing and genetic counselling. This testing will look for genetic changes that are known to cause heart conditions.

Many – but not all – genetic heart diseases are inherited. Sometimes the genetic change occurred for the first time in an individual and was not passed down from their parents.

Cardiac genetic tests are usually returned within 4 months, depending on the type of genetic tests being done.

Hypertrophic cardiomyopathy is the most common genetic heart disease.

It depends on the type of heart condition. The likelihood is not known for many conditions.

Heart conditionLikelihood of finding a genetic cause
Dilated cardiomyopathy (DCM)8-25% if there is no family history of DCM
25-40% if other family members have DCM
Hypertrophic cardiomyopathy (HCM)42-56%, depending on family history and age that symptoms start
Long QT syndrome75%
Brugada syndrome35%
Arrhythmogenic right ventricular cardiomyopathy (ARVC)67%
  • A genetic change is identified that is known to cause the heart condition.
  • No genetic change is identified. This does not mean the heart condition is not genetic. It may be caused by a gene that has not yet been identified or cannot be detected by the test used.
  • Uncertain result (also known as a variant of uncertain significance). Sometimes a genetic change is found that may be the cause of the heart condition, but there is not yet enough evidence to say for certain.
  • Incidental finding. A genetic change is identified that may increase the risk of developing a different health condition. This result is very unlikely.

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