Precision Prevention

Genotyping unveils hidden cardiac risks

by Kat Hendrix

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 “A lot of people have outdated impressions because the pace of progress has been so fast.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, M.D., 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 14 different inherited heart conditions, including cardiomyopathies, cardiac syndromes, muscular dystrophies which affect the heart, familial aortic aneurysm, familial hypercholesterolemia, unexplained cardiac arrest, transthyretin amyloidosis and Fabry disease. These evaluations are now considered a vital component of health care 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 that just one copy of a mutation can cause the disease. On average, half of those in a family with such a mutation will develop the associated condition.¹ However, genetic testing is underutilized. Leading cardiologists agree that there is a need to raise awareness of inherited cardiovascular disease among community-based cardiologists and primary care physicians.² “It’s challenging,” says Judge. “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.”

Health care needs may differ between people with inherited heart conditions and those who have the same conditions due to nongenetic factors. Treating inherited heart disease requires screening individuals and 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 morbidity and mortality in young people.³ When a pathogenic variation is identified, genetic cascade testing is recommended for relatives who might be asymptomatic carriers of the same mutation, which would put them at risk for serious complications, including sudden cardiac death. Importantly, numerous professional organizations recommend genetic cardiovascular testing 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 in the MUSC program, explains, “This service is different because we look at the full family history, not just the individual. 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. Judge says, “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.’ I listen quite a bit rather than just relying on medical records—they’re important but they don’t provide the whole story.”

Once a patient who might benefit from genetic testing is identified, specialized counselors explain the disease as well as the process and potential impacts of genetic testing. Counseling is essential because the decision to undergo genetic testing is not a simple one. Patients receive pretest counseling about the abilities, limitations and consequences of genotyping and post-test counseling to discuss the results and their impacts.

Because genotyping results can have a range of medical and psychosocial implications, genotyping should be performed by a specialized cardiovascular genetics program with appropriate counseling.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. Another advantage is that we may find other relatives who have that gene and 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, although genetic test results are very well protected in health care 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 disease. 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 family members with potentially life-saving information. The challenge is making sure physicians and patients know about this life-changing technology. “I’d like to see more awareness about genetic evaluation in general cardiology practice so that more patients can benefit from it,” says Foil.

References

1. Cirino AL, et al. Circulation. 2013;128(1):e4–e8. doi:10.1161/CIRCULATIONAHA.113.002252.

2. Judge DP. JAMA 2009; 302:2471–2476. doi:10.1001/jama.2009.1787.

3. Girolami F, et al. J Cardiovasc Med. 2018;19:1–11. doi:10.2459/JCM.0000000000000589.

4. Cirino AL, et al. JAMA Cardiol. 2017;2(10):1153–1160. doi:10.1001/jamacardio.2017.2352.

5. Ingles, J. et al. Heart Lung Circ. 2011;20(11):681–687. doi:10.1016/j.hlc.2011.07.013.

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