EMERALD: FFRCT accurately predicts which plaques cause ACS

A CT-based fractional flow reserve system was more accurate than percent diameter stenosis or adverse plaque characteristics at predicting which coronary plaques would cause ACS, according to findings presented at EuroPCR.

For the physician-initiated EMERALD study, the researchers analyzed 71 patients (mean age, 69 years; 72% men) with 226 coronary lesions (75 culprit lesions as identified by invasive coronary angiography, 151 nonculprit lesions) who experienced ACS and underwent coronary CTA 1 month to 2 years before their event.

They compared a hemodynamic assessment using CT-derived fractional flow reserve (FFRCT; HeartFlow), change in FFRCT across the plaque, axial plaque stress by CT and wall shear stress by CT with percent diameter stenosis and adverse plaque characteristics in discrimination of lesions at risk for causing ACS.

The area under the curve (AUC) was greater for the hemodynamic assessment (0.727) than for percent diameter stenosis (0.675) or adverse plaque characteristics (0.673), Bon-Kwon Koo, MD, PhD, FACC, from Seoul National University Hospital, Korea, and colleagues found. Using all three methods resulted in a higher AUC (0.746) compared with percent diameter stenosis alone (0.675) or percent diameter stenosis plus adverse plaque characteristics (0.693).

The C-index of percent diameter stenosis alone (0.677) improved to 0.725 with the addition of adverse plaque characteristics (P = .3) and to 0.766 with the further addition of the hemodynamic assessment (P = .029), according to the researchers. Using all methods also improved net reclassification index (P = .004) and integrated discrimination improvement (P < .001).

When Koo and colleagues devised a risk score giving one point each for percent diameter stenosis of at least 45%, any adverse plaque characteristic, FFR delta of at least 0.06, FFRCT up to 0.8 and axial plaque stress greater than 12,700, they found prediction of ACS-causing lesions improved with higher score (0, 16.7%; 5, 84.6%; P for trend < .001).

“When evaluating a patient for risk of ACS, we need to look at not only the burden and composition of plaque, but also the hemodynamic forces, or stress, placed upon the lesion,” Koo said in a press release. “The EMERALD study has demonstrated that by applying this important measurement, we may have the potential to greatly improve prediction of the lesions that cause ACS, which could help us optimize treatment strategies for these high-risk patients.” – by Erik Swain

Reference:

Koo BK, et al. Imaging and Functional Assessment. Presented at: EuroPCR; May 16-19, 2016; Paris.

Disclosure: Koo reports receiving an institutional research grant from HeartFlow.