Abnormal fractional flow reserve and non-hyperaemic pressure ratios in patients with severe aortic stenosis and non-obstructive coronary artery disease

Abstract

Abstract Background Fractional flow reserve (FFR) and non-hyperaemic pressure ratios (NHPRs) are well-validated tools that assess the physiological significance of coronary artery disease (CAD). Low coronary lumen to myocardial mass (V/M) ratio on CT is associated with lower FFR/NHPRs and predisposes towards ischaemia in CAD. Whilst CAD and aortic stenosis (AS) frequently co-exist, patients report angina despite obstructive disease. Purpose We therefore sought to study the interrelationship between V/M and invasive pressure indices in patients with severe AS. Methods 35 patients with severe AS were prospectively recruited as part of CAST-FFR study. Patients underwent CT coronary angiography and invasive pressure-wire assessment. All pressure-indices were assessed in the left anterior descending artery (LAD). Data was extracted to calculate FFR, iFR, diastolic pressure ratios (DPR and dPR) and Diastolic Hyperaemia-free Ratio (DFR). Patient-specific V/M were extracted off-site by independent core lab. Results Mean age was 75±7.5 years, median V/M ratio was 20.7 and mean aortic gradient and DI were 44.3±11.6mmHg and 0.23±0.4 respectively. 79% of patients had CADRADs score of <2. There were moderate positive correlations between FFR/NHPRs and V/M, including FFR (r=0.60), PdPa (r=0.48), iFR (r=0.59), DPR (r=0.59), dPR (r=0.63), DFR (r=0.67), (all p<0.005). In patients with positive pressure assessments, 69% (FFR), 71% (iFR), 70% (DPR) and 65% (DFR) had CADRADs score <2. In severe AS, lower V/M was associated with lower pressure-indices (FFR 0.75 vs 0.86, iFR 0.79 vs 0.92, DFR 0.80 vs 0.91, all p<0.005), leading to high rates of positive physiologic assessment (FFR 88%, PdPa 72%, iFR 67%, DPR 78%, DFR 74%). Conclusion Patients with severe AS exhibit high rates of abnormal FFR and NHPR values, despite having no obstructive CAD. Their propensity for having abnormal physiological results is, in part, influenced by coronary volume to mass ratio. These results are important for clinicians considering using invasive physiological tools to guide revascularisation decisions in patients with severe AS. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Monash University, Cardiac Society of Australia and New Zealand Correlation between NHPR/FFR and VMInvasive pressure indices and VM