Novel Non-invasive Test Identifies Coronary Artery Disease

August 28, 2012

Non-invasive fractional flow reserve plus CT is superior to CT alone for diagnosing significant coronary artery disease among stable patients.

Adding non-invasive fractional flow reserve to CT scan is superior to CT alone for diagnosing hemodynamically significant coronary artery disease among stable patients, said researchers in a study published online in JAMA.

Currently, physicians can use non-invasive CT angiography to check for coronary stenosis or the invasive fractional flow reserve (FFR) to measure coronary stenosis. Researchers from Cedars-Sinai Heart Institute in Los Angeles, Calif., examined the use of the novel non-invasive FFR computed from CT (FFRCT) to see if it could be effective in determining if ischemia is present.

The researchers studied 252 patients (615 study vessels) with suspected or known CAD who underwent CT, invasive coronary angiography (ICA), FFR, and FFRCT within the previous month. Anatomically obstructive CAD was defined by a stenosis of 50 percent or larger on CT and ICA. Ischemia was defined by an FFR or FFRCT of 0.80 or less.

Researchers found that 271 of the 615 vessels had less than 30 percent stenosis and 101 had at least 90 percent stenosis. Of the 252 patients, 137 had an abnormal FFR as determined by ICA. Diagnostic accuracy for FFRCT plus CT was 73 percent. When looking at CT results alone, the diagnostic accuracy for detecting coronary lesions with stenosis of 50 percent or greater was only 64 percent.

“At the patient level, FFRCT, when added to CT, improved diagnostic accuracy vs. CT alone, driven by improvements in sensitivity as well as specificity,” the authors wrote. “These results suggest that FFRCT can impart considerable discriminatory power to identify and exclude ischemia in patients with suspected CAD.”

The authors did note that the pre-specified primary endpoint for accuracy, based on the lower limit of a calculated 95 percent confidence interval, was not met, however.

An accompanying editorial suggested that studies like this one are necessary. Manesh R. Patel, MD, of Duke University Medical Center, Durham N.C, wrote, “It is in this context that FFRCT represents a novel and important innovation, with the possibility not only to diagnose but also to help direct invasive treatment. Initial reports found FFRCT to have a sensitivity of 88% and a specificity of 82% compared with the invasive FFR reference standard. However, the current larger multicenter report by Min et al confirms a high sensitivity (90%) but demonstrates modest specificity (54%), albeit better than CTA alone.”