Testing for coronary artery disease (CAD) typically starts with simple, non-invasive methods and progresses to more detailed imaging only if needed. Your doctor chooses the right test based on your symptoms, risk factors, and how likely it is that you actually have narrowed arteries. Here’s what each test involves, what it can tell you, and how they compare.
Blood Tests and Initial Workup
Before any imaging, your doctor will likely order blood work. A standard lipid panel measures your cholesterol and triglyceride levels, which are major drivers of plaque buildup. High-sensitivity C-reactive protein, a marker of inflammation, can add useful information about your cardiovascular risk even when cholesterol looks normal.
If you’re having chest pain and your doctor suspects a heart attack rather than stable CAD, a troponin blood test is the first-line tool. Troponin is a protein that heart muscle cells release when they’re damaged. Modern high-sensitivity troponin assays can detect very small amounts of heart injury, making them extremely reliable for ruling a heart attack in or out within hours.
The Electrocardiogram
An electrocardiogram (ECG or EKG) takes about 10 minutes and records your heart’s electrical activity through small stickers placed on your chest. It’s painless and usually the very first cardiac test you’ll get. The most telling sign of reduced blood flow on an ECG is a particular change in the electrical tracing called ST-segment depression of 1 mm or more. Your doctor may also look for flipped T-waves or other subtle patterns.
A resting ECG can catch signs of a previous heart attack or ongoing oxygen shortage, but it often looks completely normal in people with stable CAD who aren’t experiencing symptoms at that moment. That’s why stress testing exists.
Exercise Stress Testing
A stress test pushes your heart to work harder, usually by having you walk on a treadmill that gradually speeds up and tilts steeper. The goal is to provoke the kind of oxygen demand that would reveal a blockage. Throughout the test, an ECG monitors your heart rhythm, and your blood pressure is tracked at regular intervals.
Exercise stress testing has an overall sensitivity of about 60% to 70% and a specificity around 85%. In plain terms, it correctly identifies CAD roughly two-thirds of the time, and when it comes back negative, there’s a good chance you’re truly clear. For women specifically, accuracy drops a bit, with average sensitivity and specificity both around 61% to 69%. Because of these limitations, a stress test is most useful as a starting point. If the results are borderline or don’t match your symptoms, your doctor will move to imaging-based tests.
If you can’t exercise due to joint problems, lung disease, or other limitations, a pharmacological stress test uses medication delivered through an IV to simulate the effect of exercise on your heart. You’ll stay seated or lying down while the drug increases blood flow, and imaging captures how your heart responds.
Stress Imaging: Echo and Nuclear Scans
Adding imaging to a stress test significantly improves accuracy. There are two main approaches.
A stress echocardiogram uses ultrasound to create a moving picture of your heart before and immediately after exercise (or a stress medication). Your doctor compares the two images. If a section of heart muscle moves sluggishly after stress but looked fine at rest, that area likely isn’t getting enough blood. The test takes about 45 minutes to an hour, involves no radiation, and gives results quickly.
A nuclear stress test (also called myocardial perfusion imaging) takes a different approach. A small amount of a radioactive tracer is injected into your vein. The tracer travels through your bloodstream and is absorbed by heart muscle cells in proportion to how much blood flow they’re receiving. A specialized camera then creates a map of blood flow through your heart at rest and under stress. Areas that light up less during stress point to blockages. This test takes longer, often 3 to 4 hours because rest and stress images are captured separately, but it provides very detailed information about which parts of your heart are affected and how severely.
Coronary Calcium Scoring
A coronary artery calcium (CAC) score uses a quick, low-dose CT scan to detect calcium deposits in the walls of your coronary arteries. Calcium in these arteries is a direct marker of plaque buildup, so the test quantifies how much atherosclerosis is already present. No contrast dye or injection is needed, and the scan itself takes only a few minutes.
Results are reported using the Agatston score:
- 0: Very low risk. No detectable calcium.
- 1 to 99: Mildly increased risk. Some plaque is present.
- 100 to 299: Moderately increased risk.
- 300 and above: Moderate to severely increased risk.
- Over 1,000: A distinct very high-risk category, associated with significantly greater rates of heart disease, stroke, and death compared to scores of 400 to 999.
A calcium score is particularly useful for people in the “gray zone” of risk, where traditional factors like cholesterol and blood pressure don’t clearly point toward or away from treatment. A score of zero is powerfully reassuring, while a high score can tip the decision toward starting preventive medications like statins. The test does not, however, measure how much a blockage is restricting blood flow. Soft, non-calcified plaque can also narrow arteries, so a low calcium score doesn’t guarantee open arteries in every case.
CT Coronary Angiography
Coronary CT angiography (CCTA) goes a step further than a calcium score. It uses a CT scanner with contrast dye injected into a vein to produce detailed 3D images of your coronary arteries. This lets your doctor see the location, extent, and type of plaque (calcified or soft) as well as how much the artery is narrowed.
CCTA has excellent sensitivity and specificity for detecting significant blockages across a wide range of patients, regardless of age or sex. Its greatest strength is its negative predictive value: when CCTA shows your arteries are clear, you can be very confident they actually are. This makes it an increasingly popular first-choice test for people with stable chest pain, because a normal result can spare you more invasive procedures. The scan itself takes about 15 to 20 minutes, though you’ll need an IV for the contrast dye and may be given a short-acting medication to slow your heart rate for clearer images.
Invasive Coronary Angiography
Catheter-based angiography remains the gold standard for diagnosing CAD. A thin, flexible tube (catheter) is threaded through a blood vessel, usually in the wrist or groin, up to the heart. Contrast dye is injected directly into the coronary arteries, and real-time X-ray imaging reveals exactly where and how severely they’re blocked.
This test is typically reserved for situations where non-invasive tests have already suggested significant disease, or when you’re having symptoms serious enough that treatment (like placing a stent) might happen during the same procedure. You’re awake but sedated. Afterward, you’ll spend a few hours in a recovery room. If the catheter was inserted through the groin, you may need to lie flat for several hours to prevent bleeding at the puncture site. Wrist-access procedures generally allow you to sit up sooner.
Fractional Flow Reserve
During an invasive angiography, your cardiologist can also measure fractional flow reserve (FFR) to determine whether a specific blockage is actually restricting blood flow enough to matter. A tiny pressure sensor on a wire is advanced past the narrowed area, and blood pressure is measured on both sides of the blockage while a medication maximizes blood flow. The result is expressed as a ratio. An FFR value of 0.80 or below means the blockage is significant and likely causing reduced blood flow to the heart muscle. Values above 0.80 generally mean the narrowing isn’t functionally important, and opening it up with a stent wouldn’t provide meaningful benefit. This measurement prevents unnecessary procedures on blockages that look tight on an image but aren’t actually limiting flow.
How Doctors Choose the Right Test
The testing path depends heavily on your starting situation. If you have no symptoms and are simply assessing your long-term risk, a calcium score is often the most practical choice. It’s fast, involves no contrast dye, and the score gives a concrete number to guide prevention decisions.
If you’re having chest pain or other symptoms that could be angina, the choice between a stress test, stress imaging, and CCTA depends on factors like your exercise ability, body type, and how strongly your symptoms point toward CAD. Someone who can exercise and has an interpretable baseline ECG might start with a standard treadmill stress test. Someone who can’t exercise, or whose symptoms are more concerning, will often go straight to stress imaging or CCTA for better accuracy.
Invasive angiography with possible FFR measurement comes into play when non-invasive tests point to significant disease or when symptoms are severe and worsening. It’s both a diagnostic and a treatment tool, since stenting or surgical planning can follow directly from the findings.