Each millimeter of mitral annular calcification appears to increase risk for myocardial infarction or death by 10 percent, according to an article based on Framingham Heart Study data published in the March 11th rapid access issue of Circulation.

After adjustment for risk factors such as hypertension, high cholesterol, diabetes, obesity, physical inactivity, and smoking, mitral annular calcification was independently associated with increased risk for myocardial infarction or death. The researchers wrote that the causes of such calcification are unclear, but atherosclerosis is a likely contributor.

Caroline S. Fox, M.D., M.P.H., and her colleagues used echocardiography to measure annular calcification in participants of the Framingham Heart Study. For the purpose of the article, the condition was defined as the presence of a dense band of calcification that is clearly seen when the valve is open and closed. Calcification was measured in millimeter segments.

The new study is an analysis of data from echocardiograms of 1,197 people ? 445 men and 752 women--- who had echocardiograms during routine examinations from 1979 to 1981. The average age was 69 years for men and 73 years for women. Participants were followed for 16 years after the original echocardiogram. Cardiovascular events during the study period included myocardial infarction, coronary insufficiency, congestive heart failure and ischemic stroke. Fatal cardiovascular events included sudden cardiac death.

“Mitral annular calcification is fairly common. We found it in 14 percent of the elderly people tested,” said study coauthor Emelia J. Benjamin, M.D., Sc.M.

There were 307 new cases of cardiovascular disease and 621 deaths in the study group during follow-up; 213 deaths were attributed to heart disease.

Fox said that people with the condition were 50 percent more likely to develop cardiovascular disease during the follow-up period and were 60 percent more likely to die from a cardiovascular cause than people with no evidence of mitral annular calcification.

“Mitral annual calcification was also associated with an increased risk for all-cause mortality,” she said. Based on the findings, Fox concluded that the condition may be a marker for “preclinical cardiovascular disease.”

Both Fox and Benjamin said that there appears to be an association between MAC and traditional heart disease risk factors. “We can speculate that mitral annular calcification is a test for long-term risk factor exposure,” Benjamin said.

On that basis, the authors hypothesize that control of known risk factors such as hypertension and hypercholesterolemia could decrease the risk for development of mitral annular calcification.