Coronary CT scanning or calcium scoring test results can identify patients who have an elevated risk for cardiovascular events, as well as those who might benefit from statin therapy.
The presence of calcium in coronary arteries is a much more effective predictor of heart attack and stroke than C-reactive protein among people with normal levels of LDL cholesterol, according to a study published in the August 20 Lancet.
The findings have important implications for deciding whether cholesterol-lowering statin medication should be prescribed for people who have heart disease risk factors but normal levels of LDL, lead author Michael J. Blaha, MD, MPH, and colleagues reported.
To determine which persons have higher cardiovascular risk, and therefore, may benefit from statin therapy, Dr. Blaha, from the Johns Hopkins Heart and Vascular Institute in Baltimore, and colleagues followed 2,083 people for six years.
“This was a direct comparison to see which patients with a normal LDL level of less than 130 mg/dL would have the greater risk of having a heart attack or stroke—those with evidence of calcium in coronary arteries, as determined on a cardiac CT test, or those with high levels of C-reactive protein, which is measured in blood and is an indicator of inflammation somewhere in the body,” Dr. Blaha stated.
Coronary Calcium Buildup Increases the Risk for Heart Attack and Stroke
Ninety-five percent of the heart attacks, strokes, or heart-related deaths during the follow-up period occurred in people with some measurable level of calcium in their heart arteries, the investigators reported. In addition, 13.4% of those with the highest levels of coronary calcium (scores greater than 100 on a calcium scoring test) had a heart attack or stroke during the study, whereas only 2% of those with high C-reactive protein in their blood, but no calcium buildup, had a heart attack or stroke.
High levels of C-reactive protein in the blood had little predictive value after the investigators accounted for risk factors such as age, gender, ethnicity, hypertension, obesity, diabetes, smoking, and a family history of heart disease.
“Many patients fall into the gray zone of being healthy with normal LDL cholesterol, but also having some risk factors,” said Roger Blumenthal, MD, a co-investigator of the study. “Our study provides clear evidence that high levels of calcium in coronary arteries will increase the risk of a heart attack or a stroke … whether or not patients have high levels of C-reactive protein.”
How Effective Are Statins as Preventive Therapy?
When the researchers directly compared the prognostic importance of coronary artery calcium to C-reactive protein, the results showed that among those with no measurable coronary calcium, it would be necessary to treat 549 patients with statin medication to prevent one heart attack. However, for those with high levels of coronary calcium buildup, the predicted number needed to treat to prevent one heart attack was only 24.
“Statin medications, which are a lifelong therapy, should not be considered the same as other preventive measures, such as diet and exercise, to reduce the risk of cardiovascular disease,” Dr. Blumenthal said. “All drugs have the potential to cause side effects in some people, although with statins, the side effects are rare.”
“Without measurable amounts of calcium, which indicates atherosclerosis, you are likely to be at very low risk in the short term,” Dr. Blaha commented. “While not everyone needs a calcium scoring test, we believe looking for calcification in coronary vessels in certain patients makes sense in order to predict who may benefit from statin therapy, because the test gets right to the heart of the disease we want to treat.”