How Is a Coronary Angiogram Done?

Think of a coronary angiogram as a way of taking pictures from inside the story — instead of guessing how the heart's arteries are doing from the outside, the team looks at them directly. The short video at the top of this page runs 3 minutes 10 seconds and explains the setting for those pictures: cardiac catheterization is performed to find out whether there is disease of the heart muscle, the valves, or the coronary arteries, the pressure and blood flow in the heart can be measured during the procedure, and coronary angiography is done as part of it. Here's how that unfolds, step by step.

Step one: a thin tube reaches the heart

You lie on a table in the catheterization lab while a thin, flexible tube — a catheter — is guided through a blood vessel towards the heart. There's no large incision; the catheter travels inside the vessel itself. If you'd like a broader walk-through of that journey first, this site's "Cardiac Catheterization Steps" video gives an overview of how a cardiac catheterization is performed.

Step two: dye makes the arteries visible

Arteries don't show up clearly on ordinary X-ray pictures on their own, so a contrast dye is passed through the catheter while X-ray images are taken. The dye outlines the inside of each coronary artery as it flows through, which turns an invisible vessel into a clear picture the team can study on screen — where it runs, where it narrows, and where blood moves through freely.

Step three: reading what the pictures show

Those images are the point of the whole test. A smooth, wide outline suggests an artery letting blood through well; a pinched or irregular section points to a narrowing the team needs to think about. Because the catheter is already in place, pressure and blood flow in the heart can also be measured during the same procedure, adding numbers to what the pictures show. An angiogram itself doesn't open anything — it's a diagnostic step. What happens next depends on what it reveals, and if a narrowing is treated by opening the artery from inside, our guide to coronary stents and angioplasty explains that separate procedure.

Step four: catheter out, results explained

Once enough pictures have been taken, the catheter is withdrawn and the small entry point is looked after while you rest and are observed. The cardiology team then explains what the images showed and what, if anything, they recommend next — that conversation is individual, because the same picture can mean different things depending on your symptoms, history, and other test results.

MedicalVideos.com has published trusted medical videos since 2007. The site was founded by Dr. Mohamed Ibrahim, MD, PhD — physician and researcher.

Educational only — this article is general information about coronary angiography, not medical advice and not a guide to anyone's diagnosis or treatment. Whether an angiogram is right for you, and what its results mean, belong with your own cardiology team. If you have chest pain or other symptoms that could be from your heart, seek urgent medical care.

Frequently Asked Questions

Is a coronary angiogram the same as cardiac catheterization?

Not quite. Cardiac catheterization is the wider procedure — guiding a catheter to the heart, where pressure and blood flow can be measured. Coronary angiography, using contrast dye and X-ray pictures to look at the coronary arteries, is done during that catheterization.

Does a coronary angiogram open a blocked artery?

No. An angiogram is diagnostic — it takes pictures that show where an artery is narrowed or blocked. Opening an artery, for example with a balloon or stent, is a separate treatment step that the team would discuss if the pictures suggest it.

What can a coronary angiogram show?

It can show the coronary arteries themselves — where they run and where they are narrowed — which helps the team judge whether there is disease of the heart arteries. Combined with the pressure and blood-flow measurements taken during catheterization, it builds a clearer picture of how the heart is working.