Ranking Every Test for Heart Attack Risk

ECG Stress Tests

Stress tests are still common for assessing coronary artery disease (CAD) — but they're far from reliable.

The standard setup is simple: you walk on a treadmill that gets progressively tougher while an ECG tracks your heart's electrical signals. Doctors watch for changes in your heart rate, blood pressure, or any symptoms like chest pain or fatigue.

In theory, if you have significant blockages, your heart should struggle to get enough blood when it's working hard — and that stress will show up as abnormal ECG changes.

But here's the reality: about 70% of the lesions that actually cause heart attacks only cause mild narrowing of the arteries. They're exactly the ones that stress tests miss.

This isn't new — the landmark Ambrose Study (JACC, 1988) showed that 68% of heart attacks originated from lesions that had less than 50% stenosis on prior angiography. In other words, these soft, vulnerable plaques don't raise red flags on a treadmill.

More recent data backs this up too. One review of over 24,000 patients found that ECG stress testing only has about 68% sensitivity and 77% specificity for detecting CAD. So you end up with a test that misses many people with real disease — and flags others who don't need invasive follow-up.

And when the result is positive? Patients often get sent straight for invasive coronary angiography (cardiac cath). The problem: there's no anatomical detail behind that decision — you don't know what kind of plaque is there, how severe it really is, or if it's likely to rupture.

The takeaway: stress tests leave you guessing. Coronary CT Angiography (CCTA) is the better approach — a non-invasive scan that shows actual plaque burden, stenosis, and flow in detail. It's time to move on from outdated treadmills and start seeing what's really happening inside the arteries.

SPECT Myocardial Perfusion Imaging (MPI)

SPECT MPI is a common nuclear medicine test that measures blood flow to your heart muscle (myocardium). It works by injecting a small amount of radioactive tracer into your bloodstream and using a special camera to see how well blood reaches different parts of your heart — both at rest and under stress.

Nuclear SPECT has 82% sensitivity and 83% specificity for diagnosing coronary artery disease (CAD).

The problem is that the information stops there.

A SPECT scan shows if blood flow is reduced, but it doesn't tell you what's causing the ischemia — and crucially, it can't see plaque type. So you could have lots of soft, high-risk plaque that's prone to rupture — and if it doesn't block flow yet, SPECT might look "normal." Your doctor might say, "You have coronary artery disease, but your flow looks good — you have nothing to worry about!" — while a dangerous plaque sits there waiting to burst.

A positive SPECT result isn't straightforward either. It often triggers the next question: "Do I send them for a cath now?" This leads many patients to invasive coronary angiography to locate blockages — even if the underlying issue isn't a classic obstructive plaque. Again, you get no insight into whether that plaque is stable or vulnerable, so you're still guessing.

And let's not forget the radiation. The mean exposure for one SPECT MPI is about 13.7 mSv — roughly equal to 4.5 years of background radiation in a single 10–20 minute test.

The bottom line: SPECT does a decent job at showing where flow is limited but leaves out the most critical detail: why.

Coronary Artery Calcium Score (CAC)

Calcium scores have become popular in recent years, but they're really just the tip of the iceberg when it comes to understanding your actual heart attack risk.

First, the basics: a CAC score is a CT scan that detects calcified plaque in your coronary arteries. It gives you an "Agatston score" — the higher your score, the more hardened plaque you have in your coronary vessels.

But here's the problem: it completely misses soft, non-calcified plaque — which is often the most dangerous kind. As Dr. Janice Summers, MD puts it:

"The plaques that cause heart attacks are often the ones you can't see on a calcium score — because they haven't calcified yet. They're soft, inflamed, and prone to rupture."

By the time plaque becomes heavily calcified, it usually means you're in a late stage of atherosclerosis. The active inflammation — the real fire — has often burned out by then. What's left are stable, hardened "tree stumps." They're less likely to rupture but more likely to cause significant stenosis if they keep growing.

This is why no prospective data shows that CAC scoring actually reduces coronary events or other clinical outcomes. It's helpful for showing you have a history of plaque buildup — but it doesn't find the early, vulnerable soft plaques when you still have a chance to intervene.

And that timing matters. The real goal is to catch early atherosclerosis — when there's pathologic intimal thickening or fibrofatty plaque that could erode or rupture before it becomes unstable. That's when aggressive medical therapy and lifestyle changes can actually help.

Risk of Rupture for Stages of Atherosclerosis:

As you can see, calcified plaque is the last stage of this process. In fact, only 8–12% of thrombotic heart attacks come from calcified plaque — the other 88–92% come from the soft plaque you can't see with CAC scoring.

Fatty streaks all the way through fibrous plaques can only be seen on CCTA — so a CAC test completely misses five out of six stages of plaque development.

Bottom line: calcium scores can show you you've had a long-standing atherosclerotic process — but they won't catch the soft, inflamed plaques that actually rupture and cause heart attacks. For that, you need to see inside the artery wall with CCTA.

Cardiac MRI

Cardiac MRI is one of the most powerful tools we have for evaluating the structure and function of the heart. It's considered the gold standard for certain measurements that other tests can't match.

What is it great for?

• Heart muscle thickness (hypertrophy) — spotting abnormal thickening.
• Ejection fraction — measuring how well your heart pumps blood.
• Valve function — checking for leaks or blockages in the heart valves.
• Tissue characterization — detecting fibrosis or scarring from myocarditis or past infarctions.

But here's its main limitation: Cardiac MRI doesn't show plaque buildup inside the coronary arteries. It can't visualize or characterize plaque — so you won't know if a blockage is calcified, soft, inflamed, or prone to rupture.

So while cardiac MRI is excellent for diagnosing structural heart disease and damage from prior events, it's not the best tool for predicting heart attacks.

PET Myocardial Perfusion Imaging (MPI)

PET MPI takes SPECT MPI to the next level by giving you highly sensitive, quantitative data on blood flow, measured in milliliters per minute. It's especially useful for detecting subtle flow issues — even when your arteries look normal on other tests.

What sets PET apart is its precision. While it can't visualize plaque in the coronary arteries, it does offer a clearer picture of how well blood actually reaches the myocardium, especially under stress.

A cardiac PET MPI typically exposes you to about 3.7 mSv, which is substantially lower than a typical SPECT MPI (12.8 mSv) — that's roughly 71% less radiation for a better-quality result.

This makes a difference because it can show doctors areas of the heart that might have subtle flow problems — or damage — that other tests could overlook.

When you compare the two head-to-head, PET MPI consistently outperforms SPECT:

• ~90% sensitivity for detecting at least one coronary artery with >50% stenosis
• ~89% specificity for accurately ruling out disease

Bottom line? If you're choosing between SPECT MPI and PET MPI, PET MPI is the clear winner for sensitivity, specificity, and lower radiation exposure. Just remember: like SPECT, it still can't show you what kind of plaque is lurking.

Cardiac Catheterization

Cardiac catheterization — often called cardiac cath or heart cath — is a procedure where a thin, flexible catheter is inserted into a blood vessel and guided to the heart. It's used to diagnose and treat certain heart conditions on the spot.

A cath can assess blood flow, measure pressures in the heart chambers, and evaluate valve and artery function. It's also how cardiologists perform interventions like stent placement.

When it comes to spotting stenosis (narrowing of a vessel), cardiac cath is highly effective. It can also measure fractional flow reserve (FFR) — which shows whether a plaque is hemodynamically significant and truly blocking blood supply.

But here's the limitation: a cath does NOT tell you the composition of that plaque. So you could have a cath, be told you're "good to go" because there's no severe narrowing — and still have a heart attack days later because a hidden soft plaque ruptured.

The problem is that cath sees the inside of the artery lumen, but not what's going on behind the arterial walls. Keep in mind, all plaque develops behind the arterial walls.

To be clear, caths are critically important if you're actively having a heart attack or total occlusion. Interventional cardiologists rely on cath to stent or bypass blockages in an emergency — but that's end-stage disease. It's a last resort, not a screening tool. Therefore, we rank it #6 out of 7.

Coronary CT Angiogram (CCTA)

CCTA is a non-invasive heart imaging test that uses CT technology plus IV contrast dye to visualize the heart and coronary arteries.

What makes CCTA so powerful is that it shows exactly where plaque is building up inside your heart's arteries — instead of just guessing based on blood flow or symptoms.

When combined with AI tools, like those from Cleerly, you can precisely quantify plaque burden in every major artery and even calculate fractional flow reserve (FFR) non-invasively.

This means you can save cardiac catheterization for cases where there's clearly a severe blockage that needs fixing.

Traditionally, CAD diagnosis has relied on the tests we reviewed above such as ECG stress tests or Myocardial Perfusion Imaging (MPI) like SPECT/PET. While these can detect blood flow problems, they mostly show indirect markers — which leads to a lot of false negatives and positives.

CCTA provides a direct look at the coronary arteries themselves, which makes diagnosis far more precise.

• The CONFIRM Registry (27,000 patients) found that a normal CCTA predicts a 7+ year "warranty period" with 95% event-free survival.
• It can locate vulnerable non-stenotic plaques — the soft plaques that don't block flow enough to cause angina but still cause ~70% of heart attacks.
• It's fast: a full CCTA takes about 10 minutes from start to finish.
• The mean radiation dose is just 2.88 mSv, which is less than a year of natural background radiation.
• For patients without known CAD, CCTA has about 91% sensitivity and 80% specificity.

The detail it provides also changes how we manage risk:

• No plaque: No worry.
• Minimal calcification: Low risk, but monitor.
• Mixed (soft and hard), non-obstructive plaque: Start aggressive medical therapy — lifestyle, statins, inflammation control.
• Severe stenosis with stable plaque: Focus on treatment for angina relief, not preventing rupture. (Stents or bypasses here don't extend life expectancy — they improve quality of life by restoring flow.)

The SCOT-HEART trial (4,146 patients) confirmed the real-world impact: using CCTA as a front-line test for stable chest pain reduced heart disease death or nonfatal heart attacks by 41% at 5 years compared to standard care.

AI tools like HeartFlow's Plaque Analysis take this even further. In the DECODE study, adding Plaque Analysis to CCTA led to management changes in 66% of cases, even in patients with a zero calcium score. More than half had their treatment plans revised, and 63% had medical therapy intensified — proving you can fine-tune care when you really understand plaque composition, not just presence.

At the end of the day, plaque buildup is driven by chronic inflammation. It can go down two paths: either the inflammation settles and the plaque stabilizes (calcification), or the cycle repeats — keeping the plaque soft, unstable, and more likely to rupture.

CCTA is the only non-invasive test that can see these soft, inflamed plaques in their early stages — when you can still do something about them.

Heart Attack Risk Tests Ranked

If you want to catch CAD early and stop heart attacks before they happen, CCTA is the gold standard.