Sunday, November 1, 2009

Coronary Artery Calcium Scan

Coronary artery calcium scan is a simple 15 minute, non-invasive heart test that will assist in determining if one has coronary heart disease (plaque in coronary arteries). Coronary artery calcium (CAC) measures “hard” calcified plaque in heart arteries. This scan does not pick up soft plaque that may have formed in coronary arteries. As coronary plaque builds up, so does the threat of heart events. Arteries become more narrowed and blood has a hard time squeezing through; thus, increasing your risk for severe cardiac events (heart attack).

The Multi-Ethnic of Atherosclerosis (MESA) enrolled 6814 asymptomatic patients, of whom over half, 3563, had zero CAC score at baseline (no hard plaque found in coronary arteries). Study participants who went on to have heart catheterization (invasive procedure that visualizes inside heart arteries) due to symptoms, clinical indications, result of the coronary calcium score, abnormal stress test or preoperative risk stratification included 175 of them. In 96% of these cases, the documented baseline calcium score predicted the actual severity or extent of the obstructed coronary artery disease as found per heart catheterization. But, in the remaining 4% there was significant narrowing of heart arteries from soft plaques found via heart catheterization-despite a zero CAC score.

In symptomatic (chest pain or equivalent) or in suspected coronary artery disease (CAD) patients in the Emergency Room-a zero CAC score has a 96% negative predictive value, meaning that 4% of patients with a zero calcium score will have significant CAD, due to soft plaque. People who present with chest pain or equivalent or who are suspected of having CAD, generally need to have functional imaging (stress MPI, stress ECHO, etc.) rather than a screening calcium score.

In asymptomatic (having no symptoms) patients; but, at risk for heart disease, the CAC scan is an excellent choice. As, the main purpose for CAC scoring should be to detect early subclinical stages (before symptoms) of CAD for which specificity is virtually 100% (people w/o significant CAD will not have calcium in their vessels.)

Dr. Harvey Hecht from Lenox Hill Heart and Vascular Institute in New York, New York was quoted: “A strong argument can now be made for requiring coronary calcium screening before stress testing in asymptomatic patients. Also, less aggressive drug therapy is appropriate for zero-score patients, and at the other end of the spectrum, the presence of coronary calcium identifies the higher risk pool of patients in whom 95% to 96% of the events will emerge; it is this group that will benefit from highly targeted aggressive treatment.”

To wrap this up, if patients present to the emergency room with chest pain symptoms a functional imaging study should be recommended versus a coronary artery calcium scan. In asymptomatic patients screening for early signs of heart disease a coronary artery calcium scan would be an excellent choice. Remember, early detection is the key to preventing heart events.

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