These scans measure the amount of calcium buildup in the arteries of the heart. Calcium is one of many substances found in atherosclerotic plaques. The calcium score correlates with the amount and severity of blockages a person has. A higher score predicts an increased risk of heart problems in the future. These scans are also called ultrafast CT (computed tomography) scans because they are faster than traditional CT scanners.

Two types of scanners can be used. The original type is known as the electron-beam CT scanner because it generates X-rays by firing electron beams at tungsten rings. Another type is called a helical or spiral or multidetector CT scanner. This scanner generates X-rays in the traditional way.

This test can be thought of a screening test for heart disease, much like stress tests. One advantage of a stress test is that it shows the person's functional capacity. That is, how much stress does it take before the heart starts showing problems? If a stress test shows problems at a low level of stress, that suggests a serious problem whereas if the heart only acts up under very high levels of stress, the problem is less serious. This important information is not provided by calcium scans.

A stress test also helps to determine whether a person's symptoms are caused by blocked arteries or not. People with blocked arteries may experience chest discomfort or shortness of breath due to other, concomitant illnesses. A stress test helps sort this out. Calcium scans do not help in this regard.

However, calcium scans may detect very early atherosclersosis that may be missed by a stress test. In order for a stress test to show an abnormality, a coronary artery must be narrowed by at least 50% to 70%. Lesser degrees of blockage may be missed by stress tests but picked up by a calcium scan. These lesser degrees of blockage would not require an angioplasty or bypass. However, their presence may mandate increased attention to risk factor modification and consideration of treatment with an antiplatelet agent such as aspirin.

One study has shown that the amount of coronary calcium detected by these scans decreases when high cholesterol levels are reduced. Thus these scans may be useful to document the effectiveness of various interventions.

A negative calcium scan makes it very unlikely that a person has significant blockages but once in a while they can be missed. A positive scan means blockages may exist but further testing by angiograms or stress tests are required to determine their severity.

An alternative test to detect the earliest stages of atherosclerosis is the carotid intimal medial thickness scan.

No preparation is required to take this test. The patient lies in a device very similar to a traditional computed axial tomography (CAT or CT) scanner. The patient must hold their breath for a few seconds once or twice for the images to be acquired. Image acquisition takes less than a minute and the patient will be out of the room in 10 to 15 minutes.

A modification of these scans tusing and intravenous contrst injection hat can actually give a picture of the arteries of the heart rather than just measuring the calcium content. These scans are coming close to giving the detailed picture of the arteries that an angiogram can. While rapid progress is being made in this area, a definitive determination of whether a person truly has severe blockages and whether or not an angioplasty or bypass is needed still requires an angiogram.

Related Topic: CAT Scans

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