A couple of weeks ago, I wrote about using bloodwork, urine tests, and medical history to dive deeper into your own personal cardiac risk.
Imaging tets can add a lot more to the cardiac risk assessment - the problem is that these tests are often used incorrectly.
You’ve probably heard of things like a stress test, echocardiogram, coronary artery calcium score (often called a calcium score or a CAC), a coronary CTA (CCTA), and a carotid ultrasound.
Sometimes these tests can be helpful for an individual, but sometimes these tests are useless - or even worse, misinform us.
Unfortunately, in my day to day work, I see way too many patients who are not well served by their doctors with these tests:
Tests done for the wrong reasons
The wrong test ordered for the specific patient in mind
The wrong decisions being made based on the results of the testing
Let’s take a look at some of the cardiac imaging tests and what they tell us.
Importantly, I’ll also look at some of the ways these tests end up making our health care worse rather than better.
Coronary artery calcium score (CAC) testing is frequently misused and misunderstood
A calcium score is a low radiation CT scan that’s done to see if you have any calcium buildup in the arteries around the heart.
It’s a test that’s almost never covered by insurance, and out of pocket cost is usually $100 or $150.
You get a score that ranges from 0 (no calcium visualized) to several thousand (the highest I’ve seen was almost 6000).
In general, more calcium means higher risk of cardiovascular events and so seeing that someone has calcification in their arteries usually gives me a more aggressive target for things like lipids (cholesterol) and blood pressure.
But there are two major reasons why a calcium score can be a misleading assessment tool:
It doesn’t pick up all the plaque in the arteries, only plaque that has become calcified.1 So a calcium score of zero misses a lot of plaque, particularly the soft plaque, which is more commonly seen in young people (who often have zero calcium).
Looking at calcification is not giving us information about how blocked the arteries are. I’ve had patients with calcium scores of 0 that have 95% blockages and patients with calcium scores of 4000 that have no significant blockages.
The practical implications of those points are really important.
First, if you’re under age 50, a calcium score of 0 is almost meaningless because any plaque you might have in your arteries probably hasn’t calcified yet, so we’re not actually informing ourselves about your cardiac risk.
Second, because a calcium score tells you zero useful information about the degree of blockage in the arteries, it doesn’t help evaluate symptoms. You can’t use a CAC as a tool to figure out why someone is having chest pain because it simply doesn’t provide useful information in that realm.
A corollary to that second point is that too often a high calcium score sets off a cascade of medicalization - a high calcium score leads to a stress test, which may lead to a catheterization, which may lead to a stent being placed.
That medical cascade is the absolute wrong outcome for a patient who goes for a calcium score.
The purpose of that test is to better stratify cardiovascular risk and decide on medications and lifestyle changes.
Almost any patient who goes for a calcium score and ends up with a stress test or an angiogram is being wronged by the medical system.2
If a doctor is going to send you for a test like that, you want to be sure you can trust them not to overreact to the result.
TL;DR on calcium scores:
🚨 A CAC of 0 does NOT mean you’re free of heart disease.
CAC only detects calcified plaque, meaning it misses soft plaque, which is more common in younger people.
I’ve seen patients with CAC of 0 and severe blockages—and patients with CAC of 4000 and no major obstructions.
Key takeaway: CAC is a risk assessment tool, NOT a way to check for blockages.
Coronary CTAs can be useful tests for young people at risk of cardiovascular disease
I mentioned before that a calcium score isn’t helpful for young people because they haven’t had a chance to have their plaques develop calcium yet.
In some instances, that’s where a coronary CTA can come in.
This is a CT scan with intravenous contrast3 that looks at the arteries around the heart to identify soft plaque, calcified plaque, and the degree of blockages present.
The identification of soft plaque can provide evidence of subclinical cardiovascular disease (meaning disease not causing symptoms) that can often prompt us to start treatment to halt the progression of heart disease in it’s tracks.
The traditional use of a CTA is for evaluation of chest pain, but this tool is being increasingly considered for individualizing an asymptomatic young patient’s cardiovascular risk.4
In addition, the ability to identify the degree of blockage present is why a CTA can sometimes be a useful test for a patient with chest pain or shortness of breath.5
There are a few important caveats to keep in mind with a CTA:
There’s more radiation with a CTA than a calcium score
The CTA requires IV contrast, which can create a small amount of risk in people with kidney disease or with contrast allergies
A CTA is gated, meaning the pictures are taken with the heart’s electrical cycle, so that if there is an irregular heartbeat like atrial fibrillation, a CTA may not provide perfect information
A lot of calcium can limit the ability of the CTA to estimate the degree of blockage
CTAs are imperfect measures of blockages in the moderate range - that are really good at identifying the absence of plaque and pretty effective at identifying a severely obstructed artery, but less ability to discriminate degrees of moderate blockage6
Perhaps the most important caveat to keep in mind is something similar to what we discussed with the calcium score - what we do with the results determines whether the test was helpful or harmful.
If a CTA leads to an invasive procedure or a stent for an asymptomatic patient, that is absolutely the wrong outcome.
But CTAs can be incredibly helpful in making management decisions when they are used correctly - and they can be helpful in identifying the presence of early signs of cardiovascular disease in people who are on the fence about treatment.
TL;DR on coronary CTAs
✅ Great for young patients at risk of heart disease – Unlike CAC, it detects soft plaque before it calcifies, helping with early risk assessment.
✅ Useful for chest pain evaluation – Can identify blockages and stratify risk when symptoms are present.
✅ Not perfect – More radiation than CAC, requires contrast, and can be limited by irregular heart rhythms or extensive calcium.
🚨 Biggest mistake? Using CTA results to justify unnecessary invasive procedures in asymptomatic patients.
Stress tests are one of the most widely misunderstood - and misused - cardiovascular tests
I can’t tell you how many people I’ve seen tell me that they “passed a stress test” and were told that they are free of cardiovascular disease.
A stress test absolutely does not tell you that.
A stress test is trying to figure out if you have a blockage in one of the arteries around your heart that is limiting bloodflow.
Stress tests should only show up with abnormal results when there’s a greater than 70% blockage.
You read that correctly - you can have 69% blockages in arteries all over your heart, and a stress test won’t give you a clue about that.7
The useful information from a stress test in a patient who doesn’t have symptoms of cardiovascular disease comes from how well you did on the exercise part of the stress test, because exercise capacity is one of the best objective measures of cardiovascular risk.
Don’t mislead yourself about what information a stress test gives you - and from what I have seen, way too many doctors don’t really understand this concept.
And don’t even get me started on routine stress tests being done before surgery - which is perhaps the biggest scam in all of medicine.
An echocardiogram also doesn’t provide helpful information in understanding heart attack risk
An echocardiogram is an ultrasound of the heart muscle.
This is an incredibly useful test in cardiology - we can learn about your heart’s function, the size of the chambers, issues with your valves, why you have a heart murmur, and even whether you should be treated with diuretics.
But we can’t learn anything about the arteries to the heart or your risk of a heart attack.
Sometimes patients get frustrated that you can’t get information about all the different areas of the cardiovascular system from one test, but that’s unfortunately the reality of the way our testing works.
Don’t look at an echocardiogram as part of your heart attack risk evaluation.
A carotid ultrasound can sometimes be helpful sometimes
A carotid ultrasound is an ultrasound that actually can look at heart disease risk.
This is an ultrasound of the arteries in the neck looking for the presence of any plaque buildup.
When I see plaque buildup on a carotid ultrasound, it tells me the same thing that some coronary calcium on a calcium score tells me - there’s cardiovascular disease present, and we should be treating lipids and blood pressure a bit more aggressively.
Be careful not to over-extrapolate from carotid intima media thickness (CIMT), which doesn’t seem to be a useful marker of risk.
The most important point here - a test that’s done in a patient without symptoms should be used to decide on medical therapies, not to send someone for invasive procedures
You should look at all of these tests as tools, and the utility of a tool lies with how you use it.
✅ Before getting any cardiac imaging test, ask these two questions:
What specific decision will this test help me make? If it won’t change your treatment, do you really need it?
What happens if the test is abnormal? If the answer is "a stress test and then a stent," think twice about doing it.
If a calcium score that’s really high prompts a cardiac catheterization and a stent, that’s almost certainly over medicalization that isn’t life saving - and is probably just exposing someone to risk that they don’t need.
To use these tools correctly, you need to know what information they provide and what the limits of that information are.
Imaging tests can certainly better inform your own personal cardiovascular risk - and there’s compelling data that adding imaging to a risk assessment is life saving.
But I see these tests misused really frequently and so you should take this newsletter as a word of caution rather than as a call for more screening.
Make sure that you know what you and your doctor are looking for before you get sent for a bunch of testing.
And perhaps even more importantly, know what you’re both going to do with that information so that you don’t end up on a cascade of invasive and unnecessary medicalization.
The process of calcification takes years, if not decades to happen.
I say wronged by the medical system intentionally and I’m not being histrionic. I’ve seen way too many patients who have had unnecessary stress tests, catheterizations, and stents because of their result on a calcium score. It’s not just that this stuff causes anxiety for patients and costs money to individuals and to the health care system. Invasive procedures have risk, and unnecessary stents force people to take blood thinners that also have risks.
And thinner slices than a calcium score, so there’s more precision in the imaging.
Increasingly considered doesn’t mean that it’s paid for by insurance. And so wanting this test to decide on medical therapy is something where very few insurance companies will pay.
It’s not a perfect test for that evaluation, and often a functional assessment like a stress test can do a better job of figuring out whether the symptoms someone is having are related to a blocked artery.
The addition of more advanced assessment tools like HeartFlow and Cleerly can potentially provide additional clarity with regards to plaque severity and risk from the plaque. I say potentially, because these tools don’t have the degree of validation you would like them to have before applying them widely. That’s not a comment to say that they aren’t useful, it’s just that they don’t have the evidence based that you’d want from a high quality randomized trial of a few thousand patients to establish their usefulness in treatment decisions.
The newest - and best - version of a nuclear stress test, using PET technology, will actually look to see if there’s any calcium present in the arteries around the heart. So you kind of get a calcium score along with your PET stress. But most nuclear stress tests don’t provide this information. And regular stress tests or stress echocardiograms also don’t give you this info.