Explaining Cardiac Catheterization and Angiography

Heart Caths Are Used to Treat Various Heart Problems

Results of a coronary angiography.
Results of a coronary angiography. BSIP/UIG/Getty Images

Cardiac catheterization and angiography are invasive diagnostic tests in which catheters (long flexible, thin tubes) are passed through blood vessels and into the heart, in order to evaluate the anatomy and function of the heart and surrounding blood vessels.

Because so much useful information can be obtained from these tests, they are performed in virtually all patients being considered for cardiac surgery of any type, including bypass surgery, or angioplasty and stenting.

How Is A Catheterization Performed?

A person having these tests is to a special catheterization laboratory, and is placed on a special examination table. After local anesthesia is given, a catheter is inserted into blood vessels in the groin, arm, wrist or neck. The catheter is inserted either through a small incision, or by means of a needle-stick. Sometimes, catheters are inserted from more than one site. Once in the blood vessels, the catheters are advanced to the heart using x-ray guidance.

During the procedure, catheters are typically maneuvered to various locations within the heart, and the pressures within the various chambers of heart are measured. Measuring these intracardiac pressures can be very helpful in diagnosing certain kinds of heart disease. For instance, heart valve disease can be detected by measuring pressure differences between cardiac chambers. As an example, in mitral stenosis the left atrial pressure is higher than the left ventricular pressure when the mitral valve is open, indicating that the valve is not opening completely, and that a partial obstruction to blood flow is present when it should not be.

Blood samples can be taken through the catheter from different locations in the heart, in order to measure the amount of oxygen in the blood. Oxygen levels on the right side of the heart should be depleted, while oxygen levels on the left side of the heart (after the blood has passed through the lungs) have been replenished.

So unusual variations in blood oxygen in the various cardiac chambers can signal a "shunt," or abnormal blood flow within the heart, often caused by congenital heart defects such as an atrial septal defect.

Finally, by injecting dye through the catheter while a series of rapid x-ray images is recorded, "movies" can be made of the blood flowing through the cardiac chambers, or the through the coronary arteries — a procedure known as angiography (also called arteriography).

Once the procedure is completed, the catheter(s) are removed. Bleeding is controlled by placing pressure on the catheter insertion site for 30 - 60 minutes.

What Is A Cardiac Catheterization Used For?

Cardiac catheterization and angiography can reveal vital information about overall cardiac function, about the function of the individual cardiac chambers, about the cardiac valves (whether they are too narrow — stenosis — or too leaky — regurgitation), about congenital heart defects, and about the location and severity of blockages in the coronary arteries.

Sometimes a cardiac catheterization can be used to deliver treatment for various heart problems. Therapeutic catheterizations include procedures to treat mitral stenosis or aortic stenosis, procedures to close a patent foramen ovale, and of course, procedures to relieve blockages in the coronary arteries ( angioplasty and stent placement).

What Are the Risks of Cardiac Catheterization and Angiography?

Cardiac catheterization and angiography are relatively safe, but because they are invasive procedures involving the heart, several complications are possible. For this reason nobody should have a cardiac catheterization unless there is a reasonable likelihood that the information gained from the procedure will be of significant benefit.

Minor complications of cardiac catheterization include minor bleeding at the site of catheter insertion, temporary heart rhythm disturbances caused by the catheter irritating the heart muscle, and temporary changes in the blood pressure.

More significant complications include perforation of the heart wall (causing a life-threatening condition called cardiac tamponade ), sudden blockage of a coronary artery (leading to a heart attack ), extensive bleeding, stroke, or an allergic reaction to the dye used in angiography.

In addition, cardiac catheterization and angiography requires exposure to a certain amount of radiation. As with any medical test using radiation, cardiac catheterization may produce a tiny increase in the lifetime risk of developing cancer. 

A Word From Verywell

Cardiac catheterization and angiography are invasive cardiac tests that can be extremely helpful in diagnosing several kinds of heart disease, and in planning and even delivering therapy. 


Moscucci M. Grossman and Baim’s Cardiac Catheterization, Angiography, and Intervention, 8th ed, Wolters Kluwer/Lippincott Williams & Wilkins, Philadelphia 2013. p.223.