What is cardiac catheterization?
Cardiac is a medical term for the heart. Catheterization means to put a thin, hollow tube (catheter) into some part of your body. So in cardiac catheterization (cardiac cath):
Your doctor puts a thin plastic tube into your heart
The tube can't go straight into your heart. Doctors get the tube to your heart by putting it in either:
A big artery in your groin
A small artery in your wrist
Your arteries are connected to your heart. So the doctor can push the catheter through the artery all the way to your heart.
When the catheter is in your heart, the doctor squirts a special liquid through the catheter. The liquid (called a contrast agent) shows up brightly on x-rays and outlines the inside of your heart. The doctor usually also puts the catheter into each of the arteries that feed your heart (coronary arteries) and squirts the contrast agent into them too. That outlines the inside of those arteries. This test is called coronary angiography.
Why would I need cardiac catheterization?
Most often, doctors do cardiac catheterization to:
See whether the arteries to your heart are blocked
Treat blocked arteries if they find them
Doctors may suspect you have blocked arteries in your heart (coronary artery disease Overview of Coronary Artery Disease (CAD) The heart is a muscle that pumps blood. Like all muscles, the heart needs a steady supply of blood to work. Blood that pumps through the heart doesn't feed the heart muscle. Instead the heart... read more 
) if:
You have an abnormal ECG Electrocardiography Electrocardiography is a test that measures your heart’s electrical activity. It's quick, painless, and harmless. The results of that test are shown in an electrocardiogram. It looks like a... read more
, particularly one that show signs of a recent heart attack Heart Attack A heart attack is when blood flow to part of your heart is suddenly blocked and some of your heart muscle dies. Doctors use the term myocardial infarction to refer to a heart attack. Myocardium... read more 
Less often, you might need cardiac catheterization to see whether you have:
A birth defect
A tumor in your heart
A bad heart valve
A problem with the major blood vessels that go out of your heart
How is cardiac catheterization done?
Cardiac catheterization is done in a special unit in the hospital. You can usually go home after the test unless the doctor finds a problem that requires a hospital stay.
The nurses start 1 or 2 IVs and hook you up to machines that monitor your heart and blood pressure
The test is done while you're awake but usually you're given a medicine by vein to help you feel calm
Doctors first inject a medicine to numb the skin over the artery in your arm or groin
When the skin is numb, they make a small cut and insert the catheter
They'll thread the catheter through your major blood vessels and into your heart
Then doctors inject the contrast agent through the catheter
The contrast shows up on x-ray movies that doctors watch on a video screen
The doctor may also use catheters with certain tools on the tip such as:
An ultrasound or laser probe to look at or take pictures of the inside of the blood vessels
Cutting tools to take a small sample of your heart’s tissue to look at it under a microscope (biopsy)
After catheterization, you'll have a special dressing that applies pressure to your arm or groin to control bleeding.
Treatment during cardiac catheterization
Sometimes doctors can also treat your heart during cardiac catheterization by:
Clearing a blocked artery (angioplasty)
Opening a partially blocked heart valve (valvuloplasty)
During angioplasty, the doctor inflates a small balloon on the tip of the catheter. The balloon pushes the blockage open. Often the doctor also slips a wire mesh tube (stent) off the end of the catheter into the blocked area. The wire mesh tube helps hold the blocked area open.
During valvuloplasty, the doctor inflates a larger balloon to push a blocked valve open.
However, some problems found during cardiac catheterization require surgery. Other problems can be treated with medicines.
Are there any side effects to cardiac catheterization?
There are 3 types of side effects from cardiac catheterization. These involve:
The contrast agent
The catheter in your heart
The hole made by the catheter in your artery
The contrast agent makes your body feel very warm when it goes in. Some people feel sick to their stomach. Rarely, you might have serious side effects such as low blood pressure, a bad allergic reaction, or kidney damage.
The catheter in your heart sometimes irritates the heart muscle and causes an abnormal heart rhythm. Rarely the abnormal heart rhythm is dangerous and requires the doctor to give your heart an electric shock (this is called defibrillation).
Usually the hole in your artery hurts only a little and heals quickly. However, sometimes it starts to bleed or heals abnormally. Rarely, the artery becomes blocked so that blood doesn't get through to your arm or leg. Sometimes you will need an operation to fix these problems.
The risk of serious complications depends a lot on:
How healthy you are overall
How old you are
How bad your heart problem is
Overall, your risk of having a serious problem, such as a heart attack or stroke, or of dying from the test is low.
What can a doctor learn from cardiac catheterization?
Whether your arteries that feed your heart muscle (coronary arteries) are blocked
How well your heart is pumping blood
Whether your heart valves are blocked or leaky
If you have a birth defect or heart tumor
What the best treatment is for your symptoms
