Heart attack: A zero calcium score is no guarantee to prevent heart disease, expert weights in

A zero Coronary Artery Calcium (CAC) score is often viewed as the gold standard of reassurance that the heart is healthy. It is of course a positive finding but one should not be under the impression that this is complete protection against a heart attack.

Firstpost spoke with Dr Ashish Kumar, Senior Consultant, Cardiology, Amrita Hospital, Faridabad, who shared his expert opinion on the same.

What a zero calcium score really means

Dr Kumar explains that the calcium score measures only one aspect of heart disease.

“The calcium score is a measure of calcified plaque in the coronary arteries. Research from the landmark Multi-Ethnic Study of Atherosclerosis (MESA) suggests that individuals with a CAC score of zero typically have a very low risk of major cardiovascular events over the next 5-10 years. But ‘low risk’ does not mean ‘no risk,'" he says.

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He adds that the result should be interpreted with caution rather than certainty.

The hidden risk: Soft plaques

One of the key limitations of the scan is its inability to detect certain types of arterial plaque.

“One of the major limitations of a calcium scan is it cannot detect soft non-calcified plaques. These plaques are often unstable and more likely to rupture, leading to sudden clot formation and heart attack. Research published in the Journal of the American College of Cardiology (JACC) shows that approximately 4-8 per cent of cardiovascular events can still occur in people with a calcium score of zero, particularly when there are other risk factors," shares the doctor.

Why Indians remain at higher risk

The risk is not uniform across populations, with South Asians facing a disproportionately higher burden of heart disease.

“That’s especially true for Indians. South Asians account for nearly 60 per cent of the world's heart disease burden even though they account for only about 25 per cent of the world's population, says the Indian Heart Association. Moreover, Indians are likely to develop coronary artery disease nearly 5-10 years earlier than Western populations," states Dr Kumar.

Limitations of calcium scoring in younger and symptomatic patients

Even in patients with symptoms, a zero score may not rule out disease.

“A study in Circulation found that almost a third of symptomatic patients with a calcium score of zero had evidence of non-calcified coronary plaque on advanced CT coronary angiography. These plaques would have been missed on just a calcium scan," reveals the cardiologist.

This highlights the importance of not relying solely on one diagnostic tool.

Who should remain cautious despite a zero score

Certain high-risk groups may still have underlying disease even with a reassuring scan.

Some groups need extra caution even with a zero calcium score. They include smokers, diabetics, those with high LDL cholesterol, people with obesity and a family history of premature heart disease. In younger adults, plaque is often non-calcified and soft and therefore invisible on calcium scoring.

Heart disease risk in India

Heart disease continues to be a major public health concern in the country.

“Heart disease continues to be the number one killer in India, accounting for nearly 28 per cent of all deaths, according to estimates by ICMR. That’s why a calcium score should always be interpreted in conjunction with other factors such as blood pressure, cholesterol levels, blood sugar, lifestyle habits, family history, and symptoms," says the doctor.

A reassuring test, but not a guarantee

Doctors emphasise that while the test is useful, it should not be mistaken for complete protection.

“A zero calcium score is reassuring, but not an absolute guarantee. Heart attack risk is not determined by a single number on a report, but by the whole patient," concludes Dr Kumar.