Istanbul, Turkey - Results from a new study have shown that coronary artery calcification is associated with cardiovascular events in patients with type 2 diabetes, was a stronger independent predictor than many risk factors, and appears to add significantly to existing risk scores, including the Framingham cardiovascular risk score [1].

Presenting the findings from the Prospective Evaluation of Coronary Artery Calcium in Predicting Cardiovascular Events in Asymptomatic Patients with Type 2 Diabetes (PREDICT) trial this week at the 77th European Atherosclerosis Society Congress, in Istanbul, Turkey, lead investigator Dr Ian Godsland (Imperial College London, UK) said the findings "raise the question as to whether coronary artery calcification screening could become a powerful tool in the evaluation of cardiovascular risk in type 2 diabetes."

However, the findings from the trial, one of the first to assess the role of electron-beam computed tomography (EBCT) coronary artery calcium screening for predicting cardiovascular events in patients with type 2 diabetes, need to be balanced in light of future cost/benefit analyses, said Godsland.

In this analysis, the PREDICT investigators analyzed data from 589 patients being treated at hospital clinics in the UK and who underwent EBCT screening. Patients were 50 to 75 years old and had type 2 diabetes for, on average, approximately seven years. All were free of cardiovascular disease at baseline and representative of a typical diabetes population, say investigators, with 66% treated with an oral hypoglycemic and 14% treated with an oral hypoglycemic plus insulin.

Godsland, who noted that coronary calcification is known to be  increased in patients with diabetes, said the group analyzed the risk of coronary artery calcification by calcium-score quintiles, with the highest quintile representing scores from 1001 to 10 000 and encompassing the 9% of patients with the highest coronary calcium levels. The primary end point of the trial was the incidence of first coronary heart disease or first stroke, events that occurred in 66 patients during the four years of follow-up.

Investigators report that very low levels of coronary calcium were associated with a very low risk of cardiovascular events and that the proportion of patients with a clinical event increased across the quintiles, with calcium scores >1000 having the largest proportion of patients experiencing a cardiovascular event. Those with calcium scores exceeding 1000 were nearly 20 times more likely to have a first cardiovascular event than those with no calcification.

PREDICT: Predictors of cardiovascular outcomes by coronary artery calcification (CAC) score

CAC score Hazard ratio (95% CI) p 0-10 1.0 (reference) — 11-100 5.5 (1.2-24.2) 0.02 101-400 10.5 (2.5-44.5) 0.001 401-1000 11.9 (2.8-52.4) 0.001 1001-10 000 19.8 (4.5-65.6) <0.001

In univariate analysis, in addition to coronary artery calcification, the only predictors of coronary heart disease were age, male sex, and systolic blood pressure. C-reactive protein, homocysteine, and markers of lipid metabolism were not predictive of coronary events, said Godsland. In multivariate analysis, again along with coronary artery calcification, systolic blood pressure and insulin resistance were the only additional risk factors that significantly predicted first coronary heart disease or first stroke.

In addition, an area-under-the-curve receiver operating characteristic (ROC) analysis showed that when coronary artery calcium scores were added to the Framingham and the UK Prospective Diabetes Study risks scores, calcification added further predictive value. These data, said Godsland, open a new debate about the role of coronary calcium screening as a tool in the management of diabetic patients, although one that this study can't answer.

"Now it's not just a question of statistics, is it?" asked session moderator Dr David Wood (Imperial College London). "If you're going to introduce a screening tool to assess cardiovascular risk, you have to account for its availability and its acceptability. Here we have something that is tremendously expensive with a high risk of exposure to radiation. So however good the statistics are, can you really justify its use in the general population?"

Godsland said he is not recommending screening for the general population or even for patients with type 2 diabetes, because the jury is largely still out at the moment on the added benefit clinicians obtain from calcium screening. "I certainly take your point," he told Wood, "about expense and radiation exposure. But I think what this study has done is at least open the door a crack to see these types of questions pursued further."

Source

1) Godsland IF on behalf of the PREDICT study investigators. Prospective evaluation of coronary artery calcium in predicting cardiovascular events in asymptomatic patients with type 2 diabetes. 77th European Atherosclerosis Society Congress; April 27, 2008; Istanbul, Turkey.