830 FFR and NHPR Discordance in AS Population

Abstract

Coronary physiology in aortic stenosis (AS) is affected by pathological alterations within epicardial and microcirculatory environments. The hyperaemic response in AS is attenuated, with increases in baseline coronary flow velocities. We assessed whether alterations in AS influenced discordance between fractional flow reserve (FFR) and alternate non-hyperaemic pressure ratios (NHPR). Forty-one patients with severe AS and angiographically confirmed CAD underwent invasive pressure-wire measurements. Data were extracted to derive FFR, instantaneous wave-free ratio (iFR), diastolic pressure ratio (DPR) and resting Pd/Pa. Data were compared against lesion matched historic non-AS controls. Physiological significance was determined as FFR<0.80, iFR/DPR<0.89 and Pd/Pa<0.92. Patients with AS were older (75.3±7.5 vs 62.5±10.4yrs, p<0.0001), but otherwise comparable to controls. Mean gradient was 44.3±11.6mmHg and DI was 0.23±0.04. In the AS cohort, mean FFR was 0.82±0.09, iFR was 0.84±0.1, DPR was 0.84±0.1 and Pd/Pa was 0.90±0.05. There were no significant differences in FFR and Pd/Pa between cohorts, although resting iFR and DPR were lower in AS patients (p=0.02). Discordance between FFR, Pd/Pa, iFR and DPR was 29%, 22% and 24% respectively in the AS cohort, compared with 25%, 22.5% and 22.5% in controls (p>0.05). Detailed analysis determined that almost all discordance in severe AS was in the NHPR+/FFR- group (92%, 100% and 90%, respectively), differing significantly from controls (40%, 33% and 33%) (p<0.05). Overall discordance rates between FFR and NHPR are similar between AS and controls however almost all discordance is in the NHPR+/FFR- quadrant. Therefore, NHPR indices may overestimate lesion severity in severe AS patients.