Heart disease is diagnosed through a series of tests that typically start simple and become more detailed as needed. The first test is almost always an electrocardiogram (EKG), which takes about 10 minutes and can reveal problems with your heart’s rhythm and electrical activity. From there, your doctor may order blood work, imaging, stress tests, or more advanced procedures depending on your symptoms and initial results.
No single test catches every type of heart disease. The right combination depends on whether you’re having acute symptoms like chest pain right now, or whether your doctor is investigating a longer-term concern like shortness of breath or high cholesterol.
The EKG: First Test in Almost Every Case
An electrocardiogram records the electrical signals that coordinate each heartbeat. Small sensors attached to your chest and limbs pick up these signals and print them as a waveform pattern. The whole process takes a few minutes and is painless. Current guidelines call for an EKG to be completed and read within 10 minutes of arriving at a medical facility when chest pain is the concern, because it can immediately identify certain heart attacks that need emergency treatment.
An EKG is good at detecting irregular heart rhythms, signs of a current or past heart attack, and whether certain parts of the heart are working harder than they should. What it cannot do is show the physical structure of your heart or tell you whether your arteries are narrowing with plaque. That’s where other tests come in.
Blood Tests That Flag Heart Trouble
When heart muscle is damaged, cells release a protein called troponin into the bloodstream. Troponin is the single most important blood marker for diagnosing a heart attack. Guidelines from the American College of Cardiology and American Heart Association recommend using the 99th percentile of troponin levels as the cutoff: anything above that threshold, combined with a rising or falling pattern across repeat blood draws, points to acute heart muscle injury. Modern high-sensitivity troponin tests can detect very small amounts of damage, which means doctors can rule out a heart attack faster than they could a decade ago.
Other blood tests look at longer-term heart disease risk rather than acute damage. A lipid panel measures your LDL cholesterol, HDL cholesterol, and triglycerides to gauge how much fatty buildup may be accumulating in your arteries. A test for BNP (a hormone released when the heart is under strain) helps diagnose heart failure. And high-sensitivity C-reactive protein measures inflammation in the body, which plays a role in artery disease over time.
Echocardiogram: A Live Picture of Your Heart
An echocardiogram is an ultrasound of your heart. A technician moves a small probe across your chest while sound waves create a moving image on a screen. It shows the size of all four heart chambers, how the valves open and close, and how strongly the left ventricle (the main pumping chamber) contracts with each beat.
One of the most useful numbers from this test is the ejection fraction, which tells you what percentage of blood the left ventricle pushes out each time it squeezes. A normal ejection fraction is roughly 55% to 70%. Below 40% generally signals heart failure. This test is especially valuable for diagnosing valve problems, heart muscle disease (cardiomyopathy), fluid around the heart, and congenital heart defects. It’s noninvasive, uses no radiation, and takes about 30 to 60 minutes.
Stress Tests: Watching Your Heart Under Pressure
A stress test measures how your heart performs when it’s working hard. The simplest version has you walk on a treadmill or ride a stationary bike while connected to an EKG. If you can’t exercise, medication can simulate the effect by temporarily increasing your heart rate.
There are three main types, and they differ in accuracy:
- Exercise EKG stress test. The most basic option. A large analysis of over 24,000 patients found it catches about 68% of significant coronary artery disease cases and correctly clears about 77% of people who don’t have it. It’s a reasonable starting point for lower-risk patients.
- Stress echocardiogram. Combines exercise (or medication) with ultrasound imaging of the heart before and after exertion. Sensitivity jumps to about 83% with exercise, and specificity reaches 84%, making it noticeably more accurate than a plain EKG stress test.
- Nuclear stress test. A small amount of radioactive tracer is injected into your bloodstream, and a special camera shows how well blood flows through your heart muscle at rest and during stress. The standard version (called SPECT) has a sensitivity of about 82%. A newer version using PET scanning pushes sensitivity to 91% and specificity to 89%, the highest of any stress test type.
Your doctor picks the type based on your risk level, your ability to exercise, and what information they need. For patients with stable, non-urgent chest pain and no known heart disease, a simple exercise EKG is often enough to start.
Coronary Calcium Score
A coronary calcium scan uses a quick, low-dose CT scan to measure calcium deposits in the walls of your coronary arteries. Calcium builds up where plaque has been forming, so the scan gives an indirect snapshot of how much artery disease you have, even before symptoms appear.
Results are reported as an Agatston score:
- 0: No calcium detected. This suggests a low chance of heart attack in the coming years.
- 1 to 99: Mild plaque deposits. Some artery disease is present but the near-term risk is relatively low.
- 100 to 300: Moderate plaque deposits. This range carries a relatively high risk of heart attack or other heart disease events within the next three to five years.
- Over 300: Extensive disease with a higher heart attack risk.
Current guidelines note that a calcium score of zero is particularly useful for people with stable chest pain. It can effectively identify those who are low risk, unlikely to have significant artery blockages, and who may not need further testing right away. This test is fast (about 10 minutes), doesn’t require contrast dye, and is often available for a modest out-of-pocket cost even without insurance coverage.
CT Coronary Angiography
A CT coronary angiogram (sometimes called CTCA or CCTA) goes a step further than a calcium scan. Contrast dye is injected through an IV, and a CT scanner takes detailed images of the coronary arteries themselves. The result is a 3D map showing whether arteries are narrowed, and by how much.
This test is especially useful for people with an intermediate likelihood of coronary artery disease. It can rule out blockages without the need for a catheter. When the scan shows a narrowing greater than about 50%, the next question is whether that narrowing is actually restricting blood flow. A newer software tool called CT-derived fractional flow reserve (FFR-CT) can estimate blood flow through a narrowed segment using the same CT images, without requiring an additional invasive procedure. This technology improves the specificity of the CT scan and helps doctors avoid sending patients to the catheterization lab unnecessarily.
Cardiac Catheterization: The Definitive Test
Coronary angiography performed through a catheter remains the gold standard for diagnosing blocked arteries. A thin, flexible tube is threaded through a blood vessel in your wrist or groin up to your heart. Contrast dye flows through the catheter, and X-ray images reveal the exact location and severity of any blockages in real time.
This test is typically reserved for situations where noninvasive tests have already raised red flags. You’re likely to be referred for a catheter-based angiogram if you have chest pain that other tests can’t explain, abnormal results on a stress test, a CT angiogram showing a blocked or narrowed artery, or if you’ve been diagnosed with acute coronary syndrome. For patients confirmed as high-risk on validated scoring tools, invasive angiography is indicated based on a strong body of clinical trial evidence.
The procedure itself usually takes 30 minutes to an hour. You’re awake but sedated. Most people go home the same day, though you’ll need to rest and avoid strenuous activity for a day or two afterward. The key advantage of catheterization is that if a significant blockage is found, treatment (such as placing a stent to reopen the artery) can happen during the same procedure.
How Doctors Decide Which Tests You Need
The testing pathway depends heavily on whether your situation is urgent or stable. For acute chest pain, the process starts with an EKG and troponin blood draws. If those come back normal and your risk profile is low, guidelines say there’s no evidence that stress testing or imaging within 30 days improves outcomes. You may simply be monitored and followed up as an outpatient. Intermediate-risk patients typically need additional cardiac testing, often scheduled under observation or outpatient status rather than in the emergency department. High-risk patients go straight to invasive angiography.
For stable, ongoing symptoms like occasional chest tightness or unexplained shortness of breath, doctors estimate your pretest probability of coronary artery disease using risk scores that factor in age, sex, symptom type, and cardiovascular risk factors. Low-probability patients might start with a calcium score or a basic exercise stress test. Those with moderate probability often get a CT angiogram or a stress test with imaging. The goal is to use the least invasive test that can confidently answer the question, escalating only when results demand it.