JACC: Absence of coronary calcifications doesnt exclude obstructive CAD
The absence of coronary calcification does not exclude obstructive stenosis or the need for revascularizations in patients suspected to have coronary artery disease (CAD), based on results of a substudy of the CORE 64 registry data published in the Feb. 16 issue of the Journal of the American College of Cardiology (JACC).

“Coronary artery calcification is highly specific for atherosclerosis and is thought to be originated as part of the healing mechanism of usually subclinical plaque rupture events,” wrote the authors. “Because ruptured culprit plaques are not necessarily calcified, it is widely assumed that coronary calcification predicts events based on the overall atherosclerosis burden rather than the detection of vulnerable plaques per se.”

Ilan Gottlieb, MD, of the department of cardiology at Johns Hopkins University in Baltimore, and colleagues assessed whether the absence of coronary calcium data could rule out a coronary stenosis of 50 percent or greater or the need for revascularization.

“The main objective of this study was to evaluate the ability of a negative coronary stenosis scan to rule out significant stenosis, thus assessing the value of a calcium scan as a gatekeeper for angiographic studies in symptomatic patients with suspected CAD,” the authors wrote.

Gottlieb and colleagues found that despite published recommendations from the American Heart Association (AHA) and the American College of Cardiology (ACC), which say “exclusion of measurable coronary calcium may be an effective filter before undertaking invasive diagnostic procedures,” total coronary occlusion can occur without detection of calcifications.

During the study period between November 2005 and January 2007, data were drawn from 291 patients --78 women and 214 men -- who had an average age of 59.3 years and suspected CAD. Researchers evaluated these patients for the prevalence of coronary stenosis or the need for revascularization.

Researchers found that of the 291 patients, prevalence of a stenosis of 50 percent or greater via conventional coronary angiography (CCA) was 56 percent, the rate of stenosis that was less than or equal to 70  percent was 45 percent. Patients who exhibited a zero stenosis were younger than those who had a stenosis greater than zero.

According to the authors, “The ability of coronary stenosis to predict the presence of significant lesions was moderate with an AUC of 0.77.” In addition, “The presence of any coronary calcium significantly increased the chance of a patient having greater than or equal to 50 percent of coronary stenosis.”

Of the 72 patients who exhibited a zero coronary stenosis, 14 had a stenosis of equal to or greater than 50 percent and 11 had at least one stenosis that was equal to or less than 70 percent by angiographic findings.

Overall, results showed 100 patients who needed to be revascularized within 30 days of angiography, 88 percutaneously and 12 surgically. In addition, revascularization occurred in nine of the 72 patients with a stenosis of zero, six of the patients with a stenosis between one and 10, and 85 of the 195 patients with a stenosis of greater than 10.

Also, during the study the researchers found that 20 percent of the occluded vessels had no calcium, which alluded to the fact that calcification is not required for occlusion.

“We found a positive association between coronary calcium and stenosis, as demonstrated by the linear correlation of the maximum degree of stenosis and the total coronary stenosis per patient, as well as the strong and independent association between any coronary calcium and the presence of stenosis greater than or equal to 50 percent,” the authors wrote.

“Our results demonstrate that in patients with clinical indication for CCA, a coronary stenosis of zero cannot be used as a gatekeeper, because 19 percent of these patients had obstructive CAD." Coronary stenosis cannot safely exclude the presence of obstructive CAD,” concluded the authors.

The researchers found that CAD has a prognostic value and that the extent, location and severity of coronary obstructions are important predictors of outcome.

Following the guidelines endorsed by the ACC and AHA would “lead to a high percentage of patients with a missed diagnosis of obstructive CAD in a group of patients with a high enough clinical suspicion for CAD to assure an indication for invasive coronary angiography.”

Limitations of the study stemmed from not evaluating the prognostic importance of obstructive CAD in patients with a CS equal to zero.