Coronary artery calcium scanning -- a method that takes images of the coronaries and uses them to predict heart attack risk -- has soared in popularity over the last decade. But controversy has dogged the test for two reasons: a lack of scientific evidence that it can predict risk in people of all ethnicities and doubts about its cost-effectiveness.
One of those issues appears to be resolved. A study in last week's New England Journal of Medicine shows the test is a strong predictor of heart attack risk in an ethnically and racially diverse group of people.
The study, funded by the National Institutes of Health, is the largest evaluation of coronary calcium testing to date, involving more than 6,700 people nationwide. The researchers showed that participants with a moderate amount of calcium buildup in their coronary arteries had a seven times greater risk of heart disease than people with no deposits. And people with a large buildup had a 10 times greater risk.
Previous studies have shown that accumulation of calcium in the arteries is a predictor of heart disease. But most of those studies involved small numbers of people who were mostly white.
"This study establishes that testing also predicts future events in other racial groups," says Dr. Robert Detrano, professor of radiological sciences at UC Irvine and the study's lead author. "I think this is a good test. If calcium is high, then we have a good reason to bring it down."
The test uses CT scanning to measure the amount of calcium in the coronary arteries. It is noninvasive and takes only about 15 minutes. Patients are issued a score indicating the level of calcium buildup.
Many doctors are intrigued by the idea of adding a new tool to their arsenal for predicting heart attack risk -- because so far, assessing that risk is an inexact science at best. The standard method, called the Framingham risk score, is based on factors such as age, gender, cholesterol levels, blood pressure and smoking. This method is inexpensive and can predict the chances of a major coronary event within 10 years with 75% accuracy.
However, the Framingham risk score doesn't identify everyone at risk. An estimated 250,000 people in the United States die each year from sudden cardiac death, some with no known heart disease risk factors. Some cardiologists believe that coronary artery calcium scoring could extend and refine assessments and identify people whom the Framingham test doesn't capture.
