Cardiac Genetics

Cardiac Genetics

This information has been written for a patient with a cardiovascular disorder who is considering genetic testing. The decision to have such testing should not be taken lightly. It is essential that the issue be discussed with a cardiologist or clinical geneticist with experience in the care of families with this type of disorder.

  • Disorders of the heart and of major blood vessels can run in a family. This means that your close relatives may be at increased risk of developing the same disorder as you have, or they may be at risk of developing an associated disorder of another part of the body.
  • Genetic testing can help your doctor know whether your disorder is familial and could pose a risk for your relatives.
  • If the genetic test shows that you do have a familial disorder, your relatives could have genetic testing to determine whether they have inherited the abnormal gene causing your disorder. Relatives with the abnormal gene can then seek medical advice to reduce the seriousness of this risk.
  • Your doctor is the best person to advise you about the usefulness of genetic testing.
  • Genetic testing can raise issues for you and your family that make the test different from other medical tests. You will be asked to sign a consent form to confirm that you understand these additional implications of your genetic test.
  • The price of your genetic test is not covered by Medicare or by your private health insurance. Payment is required before we can proceed with your test.

The heart is a complex muscular organ that pumps blood to the lungs and then to the body. The major blood vessels taking blood to and from the heart are also keys to the normal function of the heart. Abnormalities in the heart or large blood vessels are described as cardiovascular disorders.

Cardiovascular disorders can be due to abnormal structure from birth (congenital heart disorders), abnormalities of cardiac muscle function (cardiomyopathies), abnormal cardiac rhythm (arrhythmias), progressive abnormalities in the large blood vessels leading to the lungs (pulmonary hypertension) or to the rest of the body (aortic disorder), or other abnormalities in medium-sized arties (vasculopathies).

In each case, the disorder may be due to combination of inherited genetic errors, environmental factors, and bad luck. The significance of each contribution by genes, environment, and luck will vary with different disorders and different patients.

The contribution of genes to cardiovascular disorders is not straightforward. For any specific disorder, there can be many different genes potentially involved i.e. an abnormality in any one of a number of genes can make a major contribution to a specific disorder. And to make matters more complex, an abnormality in one specific gene can potentially cause a number of different cardiovascular disorders.

If an abnormal gene is the major underlying cause of your disorder, the abnormal gene may have also been inherited by other family members. These relatives would then be at increased risk of developing the same disorder. As the genetic basis of cardiovascular disorders has become clearer, doctors have recognised that familial cardiovascular disorders are much more common than previously realised.

A diagnosis of a familial cardiovascular disorder does not mean that every person in the family will be affected or have the same cardiovascular disorder. One relative may carry the abnormal gene and develop a different cardiovascular disorder. Another relative may carry the abnormal gene and never develop a cardiovascular disorder because their own combination of other genes, environment, and luck may protect them. Some relatives will not have inherited the abnormal gene and are unlikely to develop any cardiovascular disorder.

Nonetheless, once an abnormal gene causing a cardiovascular disorder has been identified in a patient, the close relatives are at increased risk of developing either the same or an associated disorder.

We start by collecting a blood sample from you i.e. a patient with a cardiovascular disorder. Please note that we do not recommend starting testing in a family with a sample from an unaffected person; for technical reasons, it is difficult to interpret the outcome of such a test.

The genetic material in the blood sample is then examined to identify an abnormality (or “mutation”) in any one of the genes associated with your diagnosis. The number of genes tested, and their identities, will vary with the disorder, and also change over time as our understanding of cardiac genetics improves.

The test of these genes takes 4-8 weeks. This is a highly complex test involving analysis of many thousands of fragments of DNA, and the interpretation of complex genetic data.

The laboratory will report any mutations identified in you, and indicate the significance of these mutations as an explanation for your disorder. The laboratory may find more than one mutation which can cause your disorder or other cardiovascular disorders. There also are some mutations which cause both cardiovascular disorders and other seemingly unrelated conditions.

The laboratory may identify variations in one or more genes that are known to be benign i.e. are not associated with any disease. It is also possible that the lab will identify variations in genes that are of unknown significance; this uncertainty is not the laboratory’s fault as it reflects the current limitations of medical science. Variations that are known to be benign, or that are of unknown significance, will not be reported to your doctor.

Your doctor will tell you about the result of your test. If one or more mutations are found, your doctor will outline how this information explains your diagnosis and the medical implications for you and for your treatment.

The identification of a mutation paves the way for your relatives to have genetic testing to clarify their risk. This test is very accurate in determining the presence or absence of the family’s mutation. Of course, this testing is entirely voluntary. Genetic testing of an unaffected relative for such a mutation can raise a number of significant medical, psychological, legal, and financial considerations. For this reason, a Australian laboratory can only do such tests after the relative has had professional pre-test genetic counselling. Genetic counselling services are available in each State and Territory of Australia.

If a mutation is not identified by the laboratory, you will be advised of this by your doctor. This result reduces the probability that your disorder is familial, but it does not exclude this possibility. Your doctor may still make recommendations regarding the medical care of your relatives.

As with any medical test, a patient needs to understand why a test is being done. You need not understand the details of what the test is or how it is done, but you do need to consent to the purpose of the test. This consent is usually obtained informally during the consultation with your doctor without there needing to be a formal record of your consent.

In some ways, genetic tests are no different from other tests, but there are some things that set genetics apart. It is these factors that prompt many doctors, laboratories, professional societies, and regulatory agencies worldwide to require that the patient’s consent for testing be formally recorded. The key difference with a genetic test is that the result can;

  • both provide information about your current disorder and carry implications for your future risk of other disorders,
  • carry implications for your relatives regarding their risk of a familial disorder,
  • influence decisions made by an insurance company regarding an application from you or a relative for some types of insurance e.g. life insurance (please note that this does not apply to health insurance)
  • potentially allow a doctor to provide information about the genetic risk of disease in your family to your relatives, irrespective of your consent (there are strict restrictions on when and how this might be done).

For these reasons, we require that your consent for genetic testing for a familial cardiovascular disorder is in writing and submitted to the laboratory at the time of sample collection. The written consent needs to be provided using our consent form or a comparable form provided by an Australian clinical genetics service. Our consent form includes further details about these matters.

The price for a genetic test for cardiovascular disease is typically $1,000-$3,000. The current prices for our tests are provided here on this site. At this stage, these costs are not rebated by Medicare or private health insurers.

These tests are expensive because they involve exhaustive assessment of many different genes while the laboratory searches for the genetic cause for your cardiovascular disorder. Once a mutation has been found, relatives can be tested for the presence or absence of the specific mutation already identified in the family, and this is much cheaper. In other words, the expensive test need only be done once, and it potentially benefits many members of the extended family. Some families share the cost of testing with their relatives.

Please direct any questions or concerns to your doctor. You can also find more information about genetic testing in general, about your cardiovascular disorder, and about our cardiovascular genetic tests, here on this website, as well as www.heartregistry.org.au.