Also known as electron-beam computed tomography (EBCT), ultrafast computed tomography (ultrafast CT) is a noninvasive imaging technique that allows for clear, three-dimensional pictures of the heart and its structures. Based on the same technology found in the traditional or multislice CT scan, the ultrafast CT scanner is able to take several pictures of the heart during a single beat, or time its pictures to an electrocardiograph machine. This enhanced speed allows physicians to obtain pictures of the heart actually at work. The test is fast and relatively inexpensive.

Currently, the leading use of the ultrafast CT is to measure calcium deposits in the coronary arteries. Calcium deposits are a feature of atherosclerosis, or "hardening" of the arteries. Studies have shown that virtually all people who suffer from atherosclerosis also suffer from calcification of the arteries. The higher degree of calcification, the greater the risk of a heart attack or other cardiovascular event.

When measuring calcification, the results of an ultrafast CT are typically expressed in an Agatston score. This test can sometimes identify atherosclerotic heart disease before symptoms become apparent because it can detect growing plaque lesions before they begin to narrow the artery, thus restricting the flow of blood. Studies have shown that coronary artery calcification (CAC) scores are positively correlated with the degree of atherosclerosis, and that a complete lack of CAC is highly associated with a lack of atherosclerosis. Thus, patients with elevated CAC scores are likely at increased risk of heart attack, even if symptoms aren't present. This test may also be of value in an emergency room setting. Because people with a CAC score of zero are almost definitely not suffering from heart disease, the test can help physicians quickly determine which patients require further cardiac testing and which patients are not suffering from cardiac-related conditions.

While this application of ultrafast CT has potential, it's also important to note it has serious limitations. These tests are frequently marketed to the general public by alternative health care practitioners as a method to diagnose early coronary artery disease, before symptoms become clinically apparent (e.g., asymptomatic coronary artery disease). While the CAC can yield important information, especially when combined with other measures of cardiac risk, in general, an elevated CAC alone is not enough to justify drug therapy or further invasive testing in the absence of other signs and symptoms of heart disease. Studies have yet to show any different in outcomes.

Because of this drawback, the ultrafast CT is not currently considered sensitive enough to stand alone as a diagnostic or screening tool. Rather, the American Heart Association and American College of Cardiology have issued guidelines to help physicians select patients in whom the test may be valuable. Importantly, screening of asymptomatic people is not recommended. Instead, the test may be used in conjunction with other measures of heart health (e.g., stress testing and risk factor assessment) to develop an overall picture of heart health and guide therapy.

Besides generating calcium scores, ultrafast CT testing has also shown usefulness in judging the extent of damage caused by heart attack or the effectiveness of certain heart surgeries or other therapies.