A clean heart scan may not mean what you think — a new study found plaque often starts somewhere else first.

If you’ve considered getting a heart scan, like a coronary calcium score, to catch heart disease early, a large new study published in the New England Journal of Medicine suggests the heart itself may not be the earliest place plaque shows up — and that relying on a clean heart scan alone could miss disease that’s already been growing elsewhere in the body for years. (Based on the insights of Dr. Gil Carvalho)

What the Study Found

Researchers scanned the arteries of roughly 16,000 people with no symptoms and no known cardiovascular disease. Overall, 57% already had some detectable plaque — a striking number given that none of these individuals had been diagnosed with heart disease. As expected, this varied heavily by age: even among the youngest group studied, ages 18 to 29, 5 to 10% already had detectable plaque, rising to over 90% by the time people reached their 60s. Plaque was also somewhat more common in men than women across nearly all age groups.

The Surprising Part: Where Plaque Shows Up First

The most notable finding wasn’t just how common plaque was — it was where it tended to appear first. Researchers looked at three areas: the coronary arteries of the heart, the carotid arteries in the neck, and the femoral arteries in the legs.

In the youngest adults (18–29) who had any detectable plaque, it was almost entirely found in the peripheral arteries — the neck or legs — rather than the heart. This pattern persisted through people’s 30s, and even into their 40s for women. For men, plaque started showing up more often in the heart by their 40s, though a meaningful share was still peripheral-only. It was generally only in people’s 50s and 60s — particularly men — that plaque in the heart became more common than peripheral-only plaque. Even in their 60s, women’s plaque was roughly split evenly between peripheral-only and heart-involving.

The practical implication: someone can have a completely clean heart scan while already actively developing plaque elsewhere in their arteries — plaque that, based on this data, often goes on to eventually appear in the heart as well later in life.

A Shift in How Heart Disease Is Understood

This builds on a series of changes in how the medical field has approached detecting heart disease. Historically, people didn’t seek evaluation until symptoms appeared, by which point disease had often been progressing for decades. Coronary calcium scoring became a popular way to screen earlier — but it, too, is a relatively late-stage marker. It’s possible to have a calcium score of zero and still have substantial plaque, including soft (non-calcified) plaque that calcium scoring doesn’t detect, and in some cases still experience a heart attack despite a zero score. More sensitive imaging like CT angiography can detect that non-calcified plaque, but this new study suggests even that may only catch disease that has already been silently progressing in peripheral arteries for years.

How Plaque in the Neck and Legs Can Be Detected

The study used ultrasound imaging of the carotid arteries (neck) and femoral arteries (legs) to detect peripheral plaque, alongside CT angiography for the heart. A carotid ultrasound (sometimes measured as carotid intimal-medial thickness, or CIMT) can be ordered by a doctor for people with relevant risk factors or family history, as can a leg artery ultrasound. This isn’t a suggestion that every young, healthy person needs these scans — only that they may be worth discussing with a doctor for people with elevated risk factors or a family history of cardiovascular disease.

A Simple At-Home Test for Leg Circulation

There’s also a free, non-invasive test you can do at home to check for significant blood flow obstruction in the legs, called the ankle-brachial index (ABI):

1. Lying down, measure your blood pressure on each arm using a standard blood pressure cuff. Note the higher (systolic) number from each arm, then take the highest of the two as your reference value.
2. Measure your blood pressure on each ankle the same way, noting the systolic number for each leg separately.
3. Divide each ankle’s systolic reading by your arm reference value to get the ABI for that leg.

General reference ranges: 1.0 to 1.4 is considered normal, suggesting no significant blockage. A value of 0.9 or below is considered abnormal and suggests blockage in the leg arteries. Between 0.9 and 1.0 is borderline, suggesting arteries may be starting to narrow without yet significantly affecting blood flow. A value over 1.4 can suggest stiff, calcified arteries, sometimes seen in people with diabetes or advanced chronic kidney disease.

This test only catches obstruction significant enough to affect blood flow — it won’t detect smaller amounts of plaque, so a normal ABI doesn’t rule out early plaque buildup. If you have symptoms or other risk factors suggesting peripheral artery disease, it’s worth getting evaluated by a doctor regardless of your ABI result.

Frequently Asked Questions

This article is for general educational purposes and is not a substitute for personalized medical advice. Speak with a qualified healthcare provider about your individual cardiovascular risk and whether any additional screening is appropriate for you.