Coronary Artery Calcium Score (CAC):

CT is a highly sensitive technique for detecting coronary artery calcification and is being used to screen asymptomatic people in order to assess those at high risk for developing coronary artery disease. According to statistics provided by the American Heart Association, 40% of deaths in the United States are related to cardiovascular disease and more than 2,600 Americans die of cardiovascular disease every day. One of the ways to reduce the mortality rate for cardiovascular disease is to identify those at high risk for coronary artery disease and implement appropriate treatment before symptoms occur. The radiologist will review your calcium score in the context of your medical and family risk factors for cardiac disease and recommend appropriate follow-up or risk factor modification individually tailored to your specific situation.

How can I interpret my coronary artery calcium score (CAC)?

A CAC of zero (no calcium detected in the coronary arteries) effectively excludes the presence of calcified (hard) plaque in the coronary arteries. Non-Calcified (soft) play may still be present, but the future risk of death from a myocardial infarction (heart attack) or the chance of requiring a revascularization procedure (coronary artery bypass surgery (CABG) or angioplasty or stenting (balloon procedure) is extremely small. Most published studies report the relative risk (amount of increased risk) for MI or revascularization in comparison to patients with a CAC of zero.

The degree of increased risk for MI or revascularization for a given CAC depends on the amount of calcium present in the coronary arteries when compared to people of similar age, gender and medical history who have no detectable coronary artery calcification (CAC = 0). As the amount of calcium in the coronary arteries increases, so does the risk for MI or revascularization. While no one can predict what will happen to an individual, your CAC can be used to determine your risk for coronary artery disease compared to patients of similar characteristics who do not have any coronary artery calcification.

There are two ways of looking at the meaning of the CAC. The CAC can be viewed on an absolute scale ( 0 to > 1000), or on a relative scale (how you compare to men or women of similar age and clinical risk factors). (Risk factors for coronary artery disease include: age, smoking history, cholesterol level, blood pressure and diabetes.)

On an absolute scale, men and women with a CAC > 300 have been shown to be at significantly greater risk for death or non-fatal MI when compared to patients with a similar clinical histories, but a CAC < 300. For example, a person who is clinically at high risk for coronary artery disease and has a CAC > 300 has (on average) a 19 times greater chance of death or non-fatal MI than a person at low clinical risk for coronary artery disease and a CAC=0. On an absolute scale, men and women with a CAC > 300 have been shown to be at significantly greater risk for death or non-fatal MI when compared to patients with a similar clinical histories, but a CAC < 300. For example, a person who is clinically at high risk for coronary artery disease and has a CAC > 300 has (on average) a 19 times greater chance of death or non-fatal MI than a person at low clinical risk for coronary artery disease and a CAC=0.

Relative risk for death or non-fatal MI compared to clinically low risk patients with a CAC =0 (JAMA 2004;291:210-215)

On a relative scale, among men, the CAC is a significant predictor of both future risk for MI and revascularization. (For example, the risk for an MI for a man with a CAC greater than 75% is 7.24 times greater than a man with a similar clinical history, but who does not have any coronary artery calcification.) Among women, the CAC is a significant predictor for future risk for revascularization only.

Women: Association between CAC score and revascularization *.

Men: Association between CAC score and revascularization or MI *.

* Circulation 2003;107:2571-2576.

Coronary CT angiogram (CTA):

A coronary CTA is specialized CT scan of the heart. In general, patients should undergo a coronary calcium scoring prior to having a coronary CTA. If your calcium score is 0, additional information obtained from the CTA may be minimal. Conversely, if your coronary calcium score is extremely high, other cardiac testing may be more appropriate than a coronary CTA.

In order to obtain the best possible images, your heart rate should be below 60 beats-per-minute. Often, this requires taking a pill (called a beta-blocker) one hour before the scan. After registering at BeWell you will be seen by one of our Radiologists. He/she will review your medical history, and check your blood pressure and heart rate. If appropriate, he/she will give you a beta-blocker pill to help lower your heart rate. After 45 to 60 minutes, we will be ready to perform your coronary CTA. A technologist will place a small intravenous (IV) catheter into an arm vein so that we can inject IV contrast during the CT scan.

Although the actual scan of your heart takes 10-15 seconds, there is approximately 5-10 minutes of preparation time required. You will need to hold your breath for 20 seconds during the scan. When the scan is complete, the technologist will transfer your images to a 3-dimensional computer work station where the Radiologist will be able to analyze the images and construct a 3-dimensional model of your coronary arteries.

Unlike the coronary artery calcium scoring, the coronary CTA is able to identify both calcified (hard) and non-calcified (soft) plaque. Soft plaque is thought to be more dangerous than hard plaque, as it is more likely to rupture, causing sudden blockage of the coronary arteries. In addition, the Radiologist will be able to identify any areas of narrowing or blockage in the coronary arteries. Other information obtained from the coronary CTA include: the presence of an aneurysm of the thoracic aorta, abnormalities of the aortic value, and variations in the anatomy of your coronary arteries.

When compared to cardiac catheterization coronary CTA has been shown to be excellent at identifying patients who have significant ( > 50% arterial narrowing) from those who do not. The sensitivity of coronary CTA has been reported to be 97% and only 5% to 7% of patients in whom coronary CTA identified as low risk were found to have significant coronary disease during cardiac catheterization (JAMA, May 25, 2005 – Vol 293, No. 20 and J. Am. Coll. Cardiol. 2005:46:552-557).