Adverse Plaque Characteristics Relate More Strongly With Hyperemic Fractional Flow Reserve and Instantaneous Wave-Free Ratio Than With Resting Instantaneous Wave-Free Ratio

ObjectivesThe current substudy of the PACIFIC (Prospective Comparison of Cardiac PET/CT, SPECT/CT Perfusion Imaging and CT Coronary Angiography With Invasive Coronary Angiography) trial explores the impact of computed tomography (CT)–derived unfavorable plaque features on both hyperemic and non-hyperemic flow indices.BackgroundNext to lesion severity, plaque vulnerability as assessed using coronary CT angiography affects fractional flow reserve (FFR), which is associated with imminent acute coronary syndromes. Instantaneous wave-free ratio (iFR) has recently emerged as an alternative for FFR to interrogate coronary lesions for ischemia. It is, however, unknown whether vasodilator-free assessment with iFR is associated with plaque stability similarly as FFR.MethodsOf 120 patients (62% men, age 58.3 ± 8.6 years) with suspected coronary artery disease, 257 vessels were prospectively evaluated. Each patient underwent 256-slice coronary CT angiography to assess stenosis severity and plaque features (positive remodeling PR], low attenuation plaque LAP], spotty calcification SC], and napkin ring sign NRS]), as well as intracoronary pressure measurements (FFR, iFR, Pd/Pa, and pressure ratio during adenosine within the wave-free period iFRa]). CT-derived plaque characteristics were related to these invasive pressure measurements.ResultsAtherosclerotic plaques were present in 170 (66%) coronary arteries. On a per-vessel basis, luminal stenosis severity was significantly associated with impaired FFR, iFR, Pd/Pa, and iFRa. Multivariable analysis revealed that FFR and iFR were independently related to ≥70% stenosis (?0.10, p < 0.001 and ?0.09, p = 0.003, respectively) and plaque volume (-0.02, p = 0.020 and -0.02, p = 0.030, respectively). Additionally, PR and SC were also independent predictors of an impaired FFR (?0.10, p < 0.001 and ?0.07, p = 0.021, respectively), but adverse plaque characteristics were not independently related to the vasodilator-free iFR.ConclusionsCT-derived vulnerable plaque characteristics are independently associated with hyperemic flow indices as assessed with FFR and iFRa, but not with non-hyperemic indices such as iFR and Pd/Pa. These findings suggest that the effects of hyperemia on pressure-derived indices might depend not only on hemodynamic stenosis severity but also on plaque characteristics.