For patients with acute chest pain in whom acute coronary syndrome (ACS) has been ruled out, cardiac CT angiography (CCTA) provides prognostic value incremental to its diagnostic value. Plaque found at CCTA of these patients in an emergency setting is significantly related to the occurrence of a future major adverse cardiac event (MACE), according to a study published online July 19 in Radiology.

While previous research has focused on CCTA as a test to identify coronary artery disease, the prognostic value of CCTA data in acute chest pain patients in whom ACS has already been ruled out remained unknown, according to John W. Nance, Jr., MD, of Medical University of South Carolina in Charleston, and colleagues.

To evaluate the incremental predictive value of CCTA in these patients, the authors looked at 458 patients with acute chest pain who underwent coronary artery calcium (CAC) assessment with CCTA. Patients who did not experience ACS at hospitalization were followed for myocardial infarct, revascularization or other MACEs.

Results showed that patients with no plaque at CCTA remained free of MACEs during a 13 month follow-up, while 5 percent of the patients with no calcium had MACE. The extent of plaque was the strongest predictor of MACE independent of traditional risk factors, with a hazard ratio of 151.77 for patients with four or more segments containing plaque compared with those without plaque. Patients with mixed plaque were more likely to experience an event than those with only noncalcified plaque or exclusively calcified plaque.

“In our study, the extent of total plaque was the single most predictive cardiac CT angiographic measure for the occurrence of future MACE, while assessment of CAC was clearly inferior,” summed the authors.

While the presence of mixed plaque had strong predictive value over exclusively calcified or noncalcified plaque, Nance and colleagues found no significant differences between patients with either calcified or noncalcified plaque. The authors speculated this may be because patients with exclusively noncalcified plaque may be at an early stage of atherosclerotic disease, while calcified plaque indicates a later stage with more stabilized atherosclerotic plaque burden.

The authors noted their finding that the absence of CAC does not exclude future adverse events is in line with the results of previous population-based studies. “These observations might indicate that CAC is not a prerequisite for disease morbidity and might suggest that exclusively noncalcified plaque has the ability to manifest itself clinically independent of CAC.”

All patients in the current study were at a low to intermediate risk for coronary artery disease, and the authors indicated that the incremental prognostic value of CCTA will have to be further studied in asymptomatic high-risk individuals.