The field of genetic testing for inherited cardiovascular disease has moved forward so quickly that many physicians, patients, and policy-makers have had trouble keeping up. "A lot of people have outdated impressions because the pace of progress has been so fast. Over the last few years, the cost of genetic testing has dropped dramatically while the number of genes we can look at has risen just as fast. So, most people don't understand what it currently costs or what it can do for them," says Daniel Judge, MD, Professor of Medicine and Director of the MUSC Cardiovascular Genetics program. "The number of cardiovascular conditions that we know have a specific genetic basis has grown exponentially and we're finding more genes and more contributing factors all the time."
In fact, the MUSC Cardiovascular Genetics program now provides detailed genetic evaluation for at least fourteen different inherited heart conditions including: cardiomyopathies (hypertrophic, dilated, right ventricular, and restrictive), cardiac syndromes (Marfan, Loeys Dietz, Long QT, and Ehlers Danlos), muscular dystrophies which affect the heart (Duchenne, Becker, Limb Girdle, and Myotonic), familial aortic aneurysm, familial hypercholesterolemia, unexplained cardiac arrest, transthyretin amyloidosis, and Fabry disease. Due to advancements in genetic knowledge and testing technology, these evaluations are now considered a vital component of healthcare for families with inherited cardiovascular disease.
Most genetic heart conditions are inherited in an autosomal dominant pattern–meaning that men and women are equally affected and just one copy of the mutation can cause the disease. On average, half of the people in a family with an autosomal dominant heart condition will develop it.[1] However, genetic testing is underutilized. Leaders in the field of cardiology agree that more needs to be done to raise awareness of inherited cardiovascular disease among community-based cardiologists and primary care physicians.[2] "It's challenging," says Judge, "For instance, people are often told that a virus may have caused their heart to weaken. And, while this might be true in some cases, genetic conditions are the second leading cause of a weak heart after coronary artery disease which is the most common cause."
People with inherited heart conditions may have different healthcare needs than people who have the same condition due to non-genetic factors. Because genetic changes are passed from generation-to-generation, treating inherited heart disease requires screening the individual patient as well as their relatives to determine whether other family members also need medical care–even if they have no symptoms. Undetected, genetically-linked heart conditions are a major cause of cardiac morbidity and mortality in young people.[3] For this reason, when a pathogenic variation is identified, genetic cascade testing is recommended for relatives who might be asymptomatic carriers of the same mutation which can put them at risk for serious complications including sudden cardiac death. It is important to note that numerous professional organizations recommend genetic cardiovascular testing due to its proven ability to improve diagnosis and management in at-risk patients and their relatives.[4]
The MUSC Cardiovascular Genetics program focuses on the patient and their family as a unit. Kim Foil, MS, a Certified Genetic Counselor (CGC) who works directly with these patients and their families, explains, "This service is different because we look at the full family history, not just the individual patient. We look at the whole family to find clues to genetic problems that may have been passed along and to determine the most appropriate tests." Obtaining a detailed family history helps clinicians determine who will benefit from testing and the best testing strategy to use. "We try to figure out why a condition happens. We don't want to just say, 'here it is and this is what we're going to do'. Since heart conditions often run in families, I like to start from scratch. I ask where did things happen initially? Why did it happen? I listen quite a bit rather than just relying on medical records–they're important too, but they don't provide the whole story," says Judge.
Once a patient who might benefit from genetic testing is identified, specialized counselors meet with them to explain the disease and the process and potential impacts of genetic testing. Counseling is essential because the decision to undergo genetic testing is not a simple one. Patients may receive pre-test counseling about the abilities, limitations, and consequences of genotyping as well as post-test counseling to discuss the results and how they may impact clinical management of the individual and other family members.
Because genetic test results can have a range of medical and psychosocial implications, genotyping should only be performed by a specialized cardiovascular genetics program where appropriate counseling is available.[5] Foil explains, "It's our job to explain the 'pros' and the 'cons'. The 'pros' are that a lot of people see knowledge as power. The more we know about what's driving their condition, the better we can manage it and prevent serious problems from developing. Another advantage is that our results may point to a risk profile in a group of related people. We may find other relatives who have that gene and are possibly at risk for a sudden cardiac event. So, testing helps us figure out who may need high risk care even before any symptoms show up. The 'cons' are that some people find genetic testing to be anxiety provoking. They might feel like they're living with a ticking time bomb. Also, even though genetic test results are very well protected in healthcare and health insurance systems, that's not the case for life insurance. Genetic test results can affect someone's ability to get life insurance or impact their premiums."
Patients come to the MUSC Cardiovascular Genetics program for a wide variety of reasons. "We see the whole patient spectrum–from very early to very late stages of disease. Our cardiology colleagues inside MUSC and physicians from other institutions refer patients to us. But we've also seen people who are completely asymptomatic who come in because they're worried about developing a heart condition based on their family history. And there have been patients in end-stage heart failure whose final request is that we find the cause and make sure no one else in their family gets caught by surprise," says Judge.
Cardiovascular genetic testing can improve diagnostic precision and clinical decision-making and provide a patient's family members with potentially life-saving information. The current challenge is to make sure that physicians and patients are aware that this life-changing technology is available to them. "I'd like to see more awareness about genetic evaluation in general cardiology practice so that more patients can benefit from it. I'd like it to get more attention so that people begin to understand how it can impact them and their families," says Foil.
[1]Cirino, AL, et al. Genetic Testing for Inherited Heart Disease. Circulation. 2013;128(1):e4-e8.
[2]Judge DP, “Use of genetics in the clinical evaluation of cardiomyopathy.” JAMA 2009; 302:2471-6.
[3]Girolami, F, et al. Contemporary genetic testing in inherited cardiac disease: Tools, ethical issues, and clinical applications. J Cardiovasc Med. 2018;19:1-11.
[4]Cirino, AL, et al. Role of Genetic Testing in Inherited Cardiovascular Disease: A Review. JAMA Cardiol. 2017;2(10):1153-1160
[5]Ingles, J. et al. Guidelines for Genetic Testing of Inherited Cardiac Disorders: Review. Heart Lung Circ. 2011;20(11):681-687.
