Heart Disease: Diagnosing Heart Disease: Cardiac Computed Tomography (CT)

Computed tomography, commonly known as a CT scan, combines multiple X-ray images with the aid of a computer to produce cross-sectional views of the body. Cardiac CT is a heart-imaging test that uses CT technology with or without intravenous (IV) contrast (dye) to visualize the heart anatomy, coronary circulation, and great vessels (which includes the aorta, pulmonary veins, and arteries).

There are several types of CT scans used in the diagnosis of heart disease, including:

1. Calcium-score screening heart scan
2. Coronary CT angiography (CTA)
3. Total body CT scan

Calcium-score screening heart scan

The calcium-score screening heart scan is a test used to detect calcium deposits found in atherosclerotic plaque in the coronary arteries. State-of-the-art computerized tomography methods, such as this one, are the most effective way to detect early coronary calcification from atherosclerosis, before symptoms develop. The amount of coronary calcium has been recognized as a powerful independent predictor of future cardiac events and may be used to guide lifestyle modifications and preventive medical therapies to reduce this risk.

Your doctor uses the calcium-score screening heart scan to evaluate risk for future coronary artery disease. If calcium is present, the computer will create a calcium "score" that estimates the extent of coronary artery disease based on the number and density of calcified coronary plaques in the coronary arteries.

Absence of calcium is considered a "negative" exam. However, since there are certain forms of coronary disease, such as "soft plaque" atherosclerosis, that escape detection during this CT scan, it is important to remember that a negative test indicates a low risk but does not absolutely exclude the possibility of a future cardiac event, such as a heart attack.

The calcium-score screening heart scan takes only a few minutes to perform and does not require injection of intravenous iodine contrast.

Coronary CT angiography (CTA)

Coronary computed tomography angiography (CTA) is a noninvasive heart imaging test currently undergoing rapid development and evaluation. High-resolution, 3-dimensional pictures of the moving heart and great vessels are produced during a coronary CTA to determine if either fatty or calcium deposits (plaques) have built up in the coronary arteries.

Before the test, an iodine-containing contrast dye is injected into an IV in the patient's arm to improve the quality of the images. A medication that slows or stabilizes the patient's heart rate may also be given through the IV to improve the imaging results.

During the test, which usually takes about 10 minutes, X-rays pass through the body and are picked up by special detectors in the scanner. The newer 40- or 64-slice CT scanners produce clearer final computerized images with less exposure to radiation than the older models. These new technologies are often referred to as "multidetector" or "multislice" CT scanning.

Another new technology, known as dual-source CT, uses two sources and two detectors at the same time. This technology provides full cardiac detail with about 50% less radiation exposure than traditional CT.