Coronary Calcium Predicts Stroke Risk

March 01, 2013

Coronary artery calcium (CAC) is an independent predictor of future stroke events in the general population, results of a new study show.

In the trial, published online February 28 in Stroke, CAC predicted stroke in both men and women and was more predictive in persons younger than 65 years than in older individuals. It was also independent of the presence of atrial fibrillation and Framingham risk factors.

It was most effective in discriminating stroke risk specifically in persons in low (<10%) and intermediate (10% to 20%) Framingham risk categories, investigators report.

"When a patient stands in front of us we can find out about their risk factors such as diabetes, blood pressure et cetera, but we don't know much about their extent of vascular disease," lead investigator, Dirk M. Hermann, MD (University Hospital Essen, Germany), commented to Medscape Medical News. "We know that CAC is a good predictor of MI [myocardial infarction], but we wanted to know if it is a good predictor of stroke as well, and we found that it was. This study shows that the risks go together. If a patient is at risk of MI, they are also at risk for stroke. We now have a test that can tell us if a patient is at risk of 2 very common conditions."

"That CAC, as we now have shown, is able to predict stroke events independent of established risk factors, making this marker promising for risk stratification not only in the hands of cardiologists but also in the hands of neurologists," the authors conclude.

"This study suggests that broad CAC screening of the population may be the way forward," Dr. Hermann said. Still, he added, "We have to think carefully about whether this is feasible. We don't recommend this at the moment because of the radiation risk." However, he points out that imaging techniques are rapidly evolving and the ability to see disease processes in the body is improving "dramatically."

"New multislice CT [computed tomography] is associated with much lower radiation, so perhaps in the future broad screening programs will be possible. Then it will be public health question as to whether it is cost-effective," he said. "Even cardiologists are not routinely doing CAC screening at the moment, but it is starting to happen in certain centers practicing preventative medicine. This is modern medicine."

Heinz Nixdorf Recall Study

For the current study, 4180 persons aged 45 to 75 years from the population-based Heinz Nixdorf Recall study without previous stroke, coronary heart disease, or myocardial infarction, were evaluated for stroke events over an average 94 months.

Cox proportional hazards regressions were used to examine CAC as a stroke predictor in addition to established vascular risk factors (age, sex, systolic blood pressure, low-density lipoprotein, high-density lipoprotein, diabetes mellitus, smoking, and atrial fibrillation).

During the follow-up period 92 incident strokes occurred (82 ischemic and 10 hemorrhagic). Patients who sustained a stroke had significantly higher CAC values at baseline (median, 104.8) than those without stroke (11.2). In a multivariable Cox regression, log10(CAC+1) was an independent stroke predictor, with a hazard ratio of 1.52.

CAC was most predictive in patients at relatively low cardiovascular risk and in younger rather than older patients.

"That's probably because higher-risk and older patients have many more risk factors so the CAC result will become less relevant," Dr. Hermann speculated. "Whereas in younger and lower risk patients, there's nothing else to tell you that this person is at risk so it is more useful."

In the paper, the authors write, "These observations indicate that among cohorts without apparent risk, subjects exist that nonetheless exhibit a high stroke incidence. On the basis of our data, CAC is suitable to identify those subjects."

Few Prior Studies

Asked to comment on these findings, Ralph L. Sacco, MD, Olemberg Professor and chairman of neurology at the University of Miami's Miller School of Medicine, Florida, pointed out that few prior studies have examined this relationship between CAC and stroke risk.

"This is a large study from Germany that demonstrated the predictive value of coronary calcification scores for stroke," Dr. Sacco told Medscape Medical News. "CAC scores helped predict higher stroke risk quite well in the low and intermediate Framingham risk groups."

However, he points out, "although the CAC added some value to the prediction of stroke, it is not yet routinely used as a screening tool, mainly due to cost and the small risk of radiation exposure."

Further, findings in the European population that was the focus of this analysis can't necessarily be generalized to other racial or ethnic groups, he added.

"Further comparative studies between CAC and other cost-effective stroke risk scores are needed to help define the incremental value of this test."

Dr. Hermann has disclosed no relevant financial relationships.

Stroke. Published online February 28, 2013. Abstract