Stanford Center for Inherited Cardiovascular Disease

Genetic Testing In Depth

Genetic testing is available for most inherited cardiovascular conditions.  The goal of such testing is to find the difference in an individual’s DNA that has caused that person to develop a heart condition.  Differences in our DNA that cause health problems are often called mutations.  Inherited cardiovascular conditions are caused by mutations in various genes that are involved in the structure and function of the heart.  Genetic testing looks for mutations in the genes that have been associated with the particular heart condition that is running in the family. 

Genetic testing to help family members:  In many cases, the genetic test results do not change an individual’s diagnosis or how their heart condition is treated.  Instead, genetic testing is used to help determine which family members could develop the inherited heart condition that is running in the family. 

The first step is for someone in the family who has the inherited heart condition to have genetic testing.  If this testing finds the mutation that caused that person’s heart condition then other family members can be tested for that same mutation.  Family members who did inherited the mutation could develop the heart condition.  These family members need to be evaluated by a cardiologist for signs of the inherited heart condition.  Special cardiac tests are often needed and these usually need to be repeated every few years.  Family members who did not inherit the mutation are not at increased risk to develop the heart condition that’s in their family.  They do not need any special cardiac evaluations.

In most cases genetic testing is the only way to determine which family members did not inherit the condition.  Without genetic testing, all at-risk family members need ongoing cardiology evaluations.  Family members need to continue to have these evaluations until genetic testing shows that they did not inherit the mutation that predisposes to the heart condition in their family. 

Genetic testing to help with diagnosis and treatment:  In some cases, genetic testing can help in determining the right diagnosis and treatment.  Sometimes it’s not clear exactly what sort of heart condition someone has, even after they have had cardiac tests, such as an electrocardiogram (ECG) or an echocardiogram (ultrasound of the heart).  In these cases, genetic testing may be able to help make the right diagnosis.

The genetic testing process:  Most genetic tests are done on a blood sample (usually about 1 tablespoon of blood).  Some can be done on a saliva (spit) sample.  The sample is sent to a genetic testing laboratory that specializes in genetic testing for inherited cardiovascular conditions. DNA is extracted from the cells and the genetic code of certain genes is read and analyzed. 

When the first person in the family is tested, the goal of the analysis is to look for mutations that can cause heart problems.  This type of test usually looks at several genes that have been associated with that particular heart condition.  This process takes approximately 8 weeks to complete.

When the mutation causing the heart condition in the family has been found, family members are tested specifically for that mutation.  Instead of looking at all the genes associated with the condition, the genetic test just looks for that one mutation  This type of testing takes 2-4 weeks.

Genetic test results: Discussion of your genetic tests results is an important part of genetic counseling and your overall evaluation at the Stanford Center for Inherited Cardiovascular Disease.

In many cases the genetic test identifies a mutation that is known to cause the inherited heart condition that is running in your family. In some cases the genetic testing doesn’t find any difference in the DNA at all.   This happens because current genetic tests for most inherited cardiovascular conditions are not capable of finding the mutation causing the heart condition in 100% cases.  For example, current genetic testing finds a mutation in 75% of cases of long QT syndrome and 50-60% of cases of hypertrophic cardiomyopathy (HCM).  Even if the genetic test doesn’t find a mutation, the condition is often still hereditary and other family members are still at risk to develop the condition that’s running in the family.

Sometimes the genetic test results are complex.  The genetic testing might find two mutations or it might find a difference in the DNA that is inconclusive.  This happens because there is not enough information to know whether the difference in the DNA is one that causes health problems or is a normal difference that doesn’t affect health.

No matter what your genetic test results are, our team will make sure that you, your family, and your doctor understand what the results mean for your care and for the rest of the family.

Cost of genetic testing and insurance coverage:  Insurance coverage for genetic testing has improved significantly.  Most private insurers cover all or part of the cost of genetic tests.  Whether or not you have to pay for part of the test will depend on the test you are having done, your insurance, and the laboratory doing the test.  As part of your genetics evaluation the genetic counselor will help make sure you know the cost of genetic testing.  Our team can also help you check with your insurance company to find out how much of the test they cover. 

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