Inherited heart conditions (cardiac inherited diseases)

An inherited heart condition is passed on through your biological parents’ genes or can also arise without a family history. Learn more about diagnosis and testing for inherited heart conditions, as well as the different types, symptoms and treatments.

What is an inherited heart condition?

An inherited heart condition is also known as a genetic heart condition or a cardiac inherited disease. It is a heart condition that is passed on through your biological parents’ genes, or can arise in an individual without family history through a variation occurring in a cell during early development. Such ‘de novo’ variants can be passed on to offspring (i.e. inherited). Inherited heart conditions can affect people of any age, and some conditions can be life-threatening or cause sudden death.

What causes inherited heart conditions?

We inherit our genes from our biological parents. Our genes affect how our body works and our appearance, like eye colour and hair colour. Inherited heart conditions are caused by a change (called a 'variant') in one or more of our genes.

If one of your parents carries a faulty gene, it may be passed on to you. If you carry the faulty gene, then it can be passed on to your children.

You may have the faulty gene, but you may never develop any signs or symptoms. However, you can still pass the faulty gene on to your child without knowing if it will affect them.

How are inherited heart conditions diagnosed?

It can be hard to diagnose an inherited heart condition. Your doctor will ask you questions about your family medical history. They will also ask about any medications that you take. The doctor may suggest that you have some of the following tests. These tests vary for each condition.

• Blood or saliva test
• Cardiac MRI scan
• Electrocardiograph (ECG)
• Echocardiogram (echo)
• Exercise tolerance test
• Holter monitor

Types, symptoms and treatments

Arrhythmogenic right ventricular cardiomyopathy (ACM)

ACM is a genetic condition, which means it can be inherited. It is a disease of the heart muscle and is due to a problem with the protein in the heart muscle. The heart muscle cells are gradually replaced by fibrous and fatty tissue. This can cause the ventricles, the bottom chambers (rooms) in the heart, to become thin and stretched and not pump properly. It can cause abnormal heart rhythms.

Symptoms: Many people with ACM have no symptoms. Others may develop any of the following symptoms: chest pain or discomfort; feeling lightheaded or dizzy; fainting episodes; feeling short of breath; palpitations; an irregular heart rhythm; or swelling in the ankles, legs or stomach area. Sometimes ACM can lead to heart failure or sudden cardiac death, especially in young athletes.

Current treatments: There is currently no cure for ACM, but treatment can help you live a normal life. Your healthcare team will look at how well your heart is working and will discuss a treatment plan with you. This may include an ECG test, Holter monitoring, medications, cardioversion, or a pacemaker or ICD (implantable cardioverter defibrillator).

Brugada syndrome

Brugada syndrome is caused by a fault in the heart’s electrical system which affects the messages that happen during each heartbeat. Because of this, the electrical messages don’t get delivered to the heart muscle cells properly. This can cause a fast, irregular heartbeat, which can lead to fainting or in serious cases a cardiac arrest. Symptoms often show up in adults but can start at any age.

Symptoms: Many people with Brugada syndrome have no symptoms. Others may experience palpitations; seizures; fainting or blackouts; cardiac arrest and sudden death. 

Triggers: Some things can trigger an irregular heart rhythm and need to be avoided:

• Prescribed medications: See details below
• Alcohol 
• Recreational drugs: Cannabis or cocaine
• Dehydration: Avoid becoming dehydrated by keeping your fluid intake up. Vomiting and diarrhoea can also cause dehydration and you may require special rehydration drinks.
• Fever (high temperature): For more information on how to manage a fever in Brugada Syndrome, see the Cardiac Inherited Disease Group (CIDG) NZ website. 
• High intensity exercise: Discuss this with your healthcare professional. Try and find some lower intensity exercise instead.

Current treatments: There is currently no cure for Brugada syndrome, but lifestyle changes can help avoid the triggers and there are also some medications to avoid. If you are at a high risk of developing a dangerous heart rhythm or if you have already experienced one, then your doctor or specialist may recommend having an ICD (implantable cardioverter defibrillator) fitted. 

Medications to avoid: It is best to tell any medical professional that you have Brugada syndrome. Some medications can trigger Brugada syndrome, so it is best to avoid medications unless they are prescribed by your doctor or specialist, and to discuss any herbal supplements with your healthcare provider before taking them. For more information on medications to avoid with Brugada syndrome see www.brugadadrugs.org.

Catecholaminergic polymorphic ventricular tachycardia (CPVT)

CPVT is a rare genetic condition and is caused by too much calcium in the heart muscle cells, which can cause an irregular heart rhythm. When someone is under emotional or physical stress it can trigger an abnormally fast and sometimes dangerous heart rhythm called ventricular tachycardia. This heart rhythm can occur during exercise, including swimming and it most commonly occurs in children and young adults.

Symptoms: Some people with the condition have no symptoms, while others may experience palpitations, fainting, dizziness or blackouts, cardiac arrest and sudden death.

Current treatments: Medicines may be needed to prevent irregular heartbeats, such as beta blockers and sometimes flecainide. Insertion of an ICD (implantable cardioverter defibrillator) may be required to monitor your heart rate and stop dangerous heart rhythms. Consult your GP or cardiologist before undertaking competitive sports, strenuous exercise or swimming.

Dilated cardiomyopathy (DCM)

DCM is a condition where the heart becomes abnormally enlarged (dilated) and can no longer pump blood as well as it should. It can lead to heart rhythm problems (arrhythmias) and heart failure. Excessive alcohol intake may also result in DCM.

Dilated cardiomyopathy may be associated with some diseases, conditions, and substance use, but often the cause is unknown. There is a genetic cause in nearly a third of DCM cases, where people have inherited a genetic abnormality that makes them more likely to develop it. This is also known as familial dilated cardiomyopathy.

Clues that suggest it is genetic (familial) are if several people in the family have DCM or symptoms such as unexplained heart failure. 

Symptoms: Symptoms can vary, and some people have more symptoms than others. Symptoms can include shortness of breath, chest pain, palpitations, fatigue or swelling of the legs, ankles or stomach. 

Current treatments: Many symptoms can be managed with medications or treatments, depending on the individual. DCM is easier to treat with medication the earlier it is identified, preferably prior to symptoms developing. Treatments for abnormal heart rhythms (arrhythmias) include implantable devices such as a pacemaker or an ICD (implantable cardioverter defibrillator).

Hypertrophic cardiomyopathy (HCM)

HCM is most often an inherited heart muscle condition. It most often affects the main pumping chamber (room) of the heart called the left ventricle. The heart muscle cells form uneven layers, causing the muscle of your heart to thicken and become stiffer. It can also scar the heart muscle. The stiffness and scarring make it harder for the heart to take in and pump blood out properly and can lead to rhythm disorders. 

More detailed information is available on our hypertrophic cardiomyopathy webpage.

In around one in four people with HCM, the thickening of the heart muscle causes an obstruction which reduces the blood flow from the heart to the body. This is called hypertrophic obstructive cardiomyopathy (HOCM).

Symptoms: Many people have no symptoms, while others may experience chest pain, shortness of breath, light-headedness, fainting or palpitations.

Current treatments: There is no cure currently for HCM, but treatments are available to help control the symptoms and prevent complications. This can include medications to control your blood pressure, manage abnormal heart rate, and to reduce the amount of work your heart does. See our hypertrophic cardiomyopathy webpage for more information.

People who continue to experience many symptoms despite medications, or who are at risk of a life-threatening heart rhythm problem, may also need one of the following: an ICD, a pacemaker, a septal ablation procedure, or septal myectomy surgery. More information about these treatments is available on our hypertrophic cardiomyopathy webpage.

Left ventricular non-compaction cardiomyopathy (LVNC)

LVNC is a condition affecting the main pumping chamber (room) of the heart called the left ventricle. The walls of the left ventricle are soft and spongy instead of being smooth and compacted. This makes it harder for the ventricle to squeeze and relax during a heartbeat. The heart can’t pump oxygen-rich blood around your body as well as it should. 

The ventricle wall contains pieces of muscle bands called trabeculations, which extend into the chamber of the ventricle. Normally, during the development of the heart, these trabeculations become compacted which transforms the heart muscle from sponge-like to smooth and solid. With LVNC this doesn’t happen, and compaction does not occur. This is called non-compaction.

Symptoms: Many patients have no symptoms. Shortness of breath, fatigue, limitations in physical activity, or occasional swelling of the lower legs can occur. Heart rhythm can also be affected making it fast or irregular. This can cause a loss of consciousness and in rare cases sudden death.

Current treatments: Medications can improve the pumping function of the heart or reduce the chance of a dangerously fast heart rhythm. It is very important not to stop taking your prescribed medication as this can increase your risk. 

Insertion of an ICD (implantable cardioverter defibrillator) may be required to monitor your heart rate and stop dangerous heart rhythms. Strenuous activity should be avoided as it can lead to dangerous heart rhythms.

Long QT syndrome (LQTS)

Long QT syndrome is an inherited heart condition affecting how your heart beats. People with LQTS have an abnormally long QT interval, which can sometimes be seen on an ECG (electrocardiograph). Often the ECG can appear normal. It is most commonly diagnosed in children and young adults. It affects the electrical system that controls when the heart contracts (squeezes) and relaxes to pump blood around. The electrical system needs time to recover and recharge before the next heartbeat. With LQTS the heart takes longer to recharge, which can cause irregular heartbeats (arrhythmia).

Symptoms: Many people with LQTS have no symptoms, while others may experience palpitations, fainting, blackouts, seizures, or cardiac arrest and sudden death.

Triggers: The abnormal heart rhythm can be triggered by stress, sudden loud noise, strenuous exercise (especially swimming), a slow heart rate during sleep, or some medications. Different people will have different triggers. 

Medications to avoid: For people with genetic LQTS, arrhythmias can be triggered by common medications. Acquired or drug-induced LQTS is where people without genetic LQTS have similar risks from taking high doses or multiple types of certain medications.

Certain types of medications are known to prolong the length of the QT interval of the heart’s electrical system. These include antibiotics, antidepressants, antihistamines, antipsychotics and diuretics (water pills). It is also best to avoid supplements and herbal remedies. A detailed list of specific medications to avoid is available here. 

Current treatments: Beta blocker medication can help control an irregular heartbeat and slow the heart rate. If medication cannot control the risk of a life-threatening arrhythmia, you may require a pacemaker or ICD (implantable cardioverter defibrillator). For some people who cannot take medication, surgery may be needed to remove certain nerves that affect the heart. This reduces the risk of a sudden cardiac arrest.

Potassium supplements can be beneficial for some people with LQTS. Talk with your doctor or specialist about prescribing potassium supplements or eating more potassium-rich foods like vegetables, pulses, and bananas. Certain activities may be better avoided if they are considered potentially to be a trigger, such as swimming.

Genetic testing for inherited heart conditions

Genetic testing can be useful for some inherited heart conditions. However, it is still evolving and there are limitations. 

Genetic testing in a family has to start with someone who has a diagnosis of an inherited heart condition. If someone in your family has been diagnosed with an inherited heart condition, then you and your family members could choose to have a blood test to see if you carry the same genetic change. The result determines if you are at risk of developing the condition and require tests or treatments.

Genetic tests have important consequences so should only be undertaken after a discussion with a healthcare professional trained and experienced in the process, such as a genetic counsellor or other inherited disease specialist.

To enquire about genetic testing, contact a regional coordinator: www.cidg.org.nz/contact

How can I look after myself or family members?

Do a CPR course: Knowing how to perform CPR (cardiopulmonary resuscitation) is a great skill to have and it can save a life if someone near you has a cardiac arrest. 

• CPR courses are available throughout New Zealand, including how to use an AED (automated external defibrillator). Attending a CPR course in person rather than online will give you a clearer idea of how to deal with this situation in real life.
• Hato Hone St John has information on how to perform CPR and use an AED.
• AED locations in NZ.

Medic Alert® medical ID bracelet/necklace: A medic alert bracelet or necklace informs the public or medical staff of your inherited heart condition and any medications to avoid.

Further information

For further information, the Cardiac Inherited Disease Group (CIDG) NZ has information for patients and families with inherited heart conditions. Their aim is to simplify screening for at-risk individuals and their families, raise awareness of these genetic heart conditions and the risk of sudden cardiac death. See www.cidg.org.nz for further information. 

CIDG also manage the Cardiac Inherited Disease Registry New Zealand. People who are suspected of having an inherited heart condition, and members of their family, can consent to participate in this registry. It may help specialists to keep track of how the condition is affecting their family and what tests or treatments should be recommended. Participants may also be able to contribute to research so that treatment guidelines can be improved in the future. 

You can read some personal stories of people living with inherited heart conditions on the Heart Foundation website.

Read inherited heart condition stories