Anatomical plaque and vessel characteristics are associated with hemodynamic indices including fractional flow reserve and coronary flow reserve: A prospective exploratory intravascular ultrasound analysis

Abstract

ObjectivesTo assess the relationship between anatomical form and physiological function in atherosclerotic coronary arteries. BackgroundAlthough adverse cardiovascular events are predicted by plaque morphology or invasively-derived hemodynamic indices, the link between these important prognostic measures remains unexplored. MethodsPatients with stable angina underwent fractional flow reserve (FFR), coronary flow reserve (CFR), pressure-derived collateral flow index (CFIp), trans-myocardial biomarker sampling and radiofrequency intravascular ultrasound (IVUS) imaging prior to intervention. Physiological ischemia was defined as either FFR≤0.8 or CFR<2.0. ResultsMean FFR was 0.70±0.15 and CFR was 2.1±1.3, with 68/92 lesions having FFR≤0.8 and 61/92 having CFR<2.0. On IVUS, FFR≤0.8 lesions had reduced minimal luminal area (MLA, p=0.03), increased plaque burden (PB, p=0.04) and volume (p=0.01). There was no relationship between FFR and IVUS-defined plaque composition. FFR≤0.8 was observed in 75.3%, 72.4% and 70.4% of lesions with MLA≤4mm2, PB≥70% and thin-cap fibroatheroma, respectively. Multivariate regression demonstrated FFR≤0.8 was independently predicted by MLA (odds ratio (OR) 0.53, 95% CI 0.29–0.97, p=0.04) and PB (OR 1.10, 95% CI 1.01–1.21, p=0.03). There were no identifiable relationships between plaque structure and CFR or CFIp. CFR<2.0 was associated with whole vessel necrotic core increases (p=0.047), fibrofatty tissue reduction (p=0.004) and elevated baseline transmyocardial high-sensitivity C-reactive protein (hsCRP) gradients (p=0.02). ConclusionsMeasures of plaque structure including PB and MLA are independently associated with FFR, but not with CFR or CFIp. Instead, vessels with low CFR have increased lipid accumulation and a higher transmyocardial hsCRP gradient. These results may explain similarities in clinical outcomes between physiologically and anatomically orientated trials.