New Measurements Such As the Coronary Calcium Score Can Determine Risk for Heart Attack

Many patients at very high risk for coronary events are not identified by history, physical examination, laboratory results, nuclear stress testing, or even cardiac catheterization with angiography. Myocardial infarction and sudden cardiac death occur when a vulnerable plaque in a coronary artery ruptures and the inflamed lipid content contacts blood and leads to thrombosis. Only 14% of heart attacks are caused by a fixed blockage of 70% or greater. In 70% of myocardial infarction patients, the coronary artery blockage is of less than 50% and the heart attack itself is the first symptom.^[1] A woman may have a totally normal cardiac catheterization and still have a 20% 6-year risk of myocardial infarction, sudden death, stroke, or congestive heart failure.^[2]

Since the fundamental risk is the extent of unstable plaque,^[3] the ideal way to identify high-risk patients would be a technology that allows us to identify these lesions. Atherosclerotic plaques are dynamic deposits in the arterial wall that go through progressive and predictable stages. Plaque instability and rupture are followed by calcification, perhaps nature's way of providing stability to an unstable plaque. The coronary calcium score determined by CT imaging can provide an estimate of total coronary plaque burden. Pathology studies have shown that the extent of coronary calcium within plaques is related to healed plaque ruptures.^[4]

We cannot identify the vulnerable plaque, but we can quantify the history of ruptured plaques -- which indicates the risk for future plaque rupture and thrombotic obstruction. Therefore, we can identify the "vulnerable patient."

Any patient with a coronary calcium score over 100 or greater than the 75th percentile should be considered to have a substantial risk of coronary events and should reduce their risk factors to secondary prevention targets.^[5] The work-up for coronary disease should not be considered complete until a calcium score has been done, especially in women.

That's my opinion. I'm Dr. Bill Bestermann, Medical Director, Vascular Medicine Center, Holston Medical Group, Kingsport, Tennessee.

© 2007  Medscape

Cite this: New Measurements Such As the Coronary Calcium Score Can Determine Risk for Heart Attack - Medscape - Dec 10, 2007.