Can a genetic test predict a person’s overall risk of getting cardiovascular diseases in the future? Scientists have been working on something called a Polygenic Risk Score (PRS) that looks at small genetic variations a person has inherited and assigns scores to them to determine whether a person may benefit from lifestyle changes, continued imaging or statin therapy.
Years of research have shown that beside risk factors like obesity, diabetes or smoking, there is a hereditary component to atherosclerotic diseases that accelerate the build-up of plaques and cholesterol, leading to heart attacks. Researchers think that a test like PRS that takes into account this genetic history is likely to better predict the future. Doctors currently determine the risk of heart attacks by analysing a person’s risk factors.
Practising cardiologists, however, are still not convinced of its use, especially as a broad screening mechanism. “Genetic history is important but if you have a good lifestyle — if you have been eating healthy, exercising regularly, not smoking — then you will overcome this genetic predisposition,” says Dr RR Kasliwal, Chairman of Clinical and Preventive Cardiology at Medanta Hospital, Gurugram. “If we talk about India, we see heart attacks at a very young age — nearly 25 per cent of all heart attacks happen in people below the age of 45 years. This means the plaque formation started in them at a very early age. So, we have to ensure that even as children, parents ensure a healthy diet and exercise. Parents shouldn’t aspire to chubby cheeks in children,” he adds.
For now, he feels the test may have a limited use and help predict interventions in people who already have several risk factors. “The only meaningful intervention, other than lifestyle changes, is to prescribe statins. And, when we talk about early prescription of statins, we are already doing it in India because of the young heart attacks. We prescribe statins even at the age of say 35 years if a person has several risk factors and a high calcium scoring. Lifestyle changes in such people may not help in preventing heart attacks in the immediate future,” he says.
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Dr Kasliwal says that his studies have shown CT calcium scoring to be a very good predictor of heart attacks. “If you do a treadmill test, for example, it will detect a blockage only when it is over 70 per cent but a CT calcium scoring can show the true picture of plaque formation in the heart. And, when done in the high risk individuals it can help us determine the course of action.”
Dr VK Bahl, Principal Director of Cardiac Sciences at Max Hospitals, and former Head of Cardiology at AIIMS-Delhi, agreed that the test has a limited role at present. “You have to show that an intervention actually helps us detect cases where we can make meaningful changes and reduce morbidity and mortality from the disease. Now, let’s say we have a way to detect early plaque formation —what will you do with this information? Several studies have shown that in people with asymptomatic plaques or even stable angina — chest pain on exertion — even a procedure like stenting doesn’t help in reducing mortality. That is because someone might have a big plaque that blocks 70 per cent of a vessel and not get a heart attack while someone with 10 per cent blockage might. This is because heart attacks happen when a plaque becomes unstable and breaks up. So, a pre-emptive stenting doesn’t help. Only prescribing statins helps — it not only reduces the cholesterol levels it also stabilises the plaques, preventing them from breaking off.”
He adds the disclaimer that stenting when a person is having a heart attack is absolutely life-saving, it is not of any use before that point. According to him, statins may be prescribed even at a young age if a person fulfils any of the four criteria — they have Type 2 diabetes, cholesterol levels are more than 190, have several risk factors like obesity, family history, and smoking, or they have had a heart attack. There are borderline patients where additional markers like CT calcium scoring might be done to start intervention.