Coronary fraction flow reserve (FFR), the ratio of the mean coronary pressure distal to a coronary stenosis to the mean aortic pressure during maximal coronary blood flow (hyperemia), defines the hemodynamic significance of coronary artery narrowing. Recent landmark studies showed a clear benefit of FFR in guiding percutaneous coronary intervention (PCI) for better clinical outcome and cost-effectiveness. The reference method for FFR measurement requires the use of a pressure wire inserted across the stenosis invasively. Therefore, a non-invasive method to quantify FFR is clinically desired.~Noninvasive assessment of FFR via a combination of computational fluid dynamics (CFD) and coronary CT angiography CCTA (the so-called FFRCT) has potential. Coronary computed tomographic angiography is a noninvasive test for diagnosis of anatomic coronary stenosis (i.e., narrowing of a blood vessel). However, CCTA alone does not determine whether a stenosis causes ischemia. Computational fluid dynamics (CFD), applied to CCTA images, enables computation of FFR (FFRCT). Recent studies have demonstrated the potential of FFRCT as a promising noninvasive method for identification of individual lesion with ischemia from both single centre and multi-centre prospective studies. However, the FFRCT is currently performed remotely and it takes several hours to complete the computation for each study. This potentially impedes the wider clinical application of FFRCT.~A new analytical model of FFR from the general Bernoulli equation (conservation of energy) (FFRB) is simple and has potential. The Bernoulli equation has many clinical applications. A collaborator group has recently developed a new analytical model to quantify pressure drop, and hence FFR, based on lesion dimensions (i.e., the cross-section area along the lesion and the length of lesion) and coronary flow, with no empirical parameters. The investigators validated it using in vitro and in vivo experiments and finite-element method. The study team hypothesize that this new model will allow quantification of FFR (FFRB) in a cohort of human patients with intermediate coronary stenosis. The investigators will compare FFRB with invasive FFR measurements from invasive coronary angiography (ICAG).~Aims and Objectives~Primary aim: Diagnostic performance of FFRB with CCTA data in patients with intermediate coronary artery disease (CAD), as compared to an invasive FFR reference standard (FFR<=0.80)~Secondary aims: Diagnostic performance with FFRB for lesions of intermediate stenosis severity; Determining the per-vessel correlation of FFRB value to FFR from ICA
Coronary fraction flow reserve (FFR), the ratio of the mean coronary pressure distal to a coronary stenosis to the mean aortic pressure during maximal coronary blood flow (hyperemia), defines the hemodynamic significance of coronary artery narrowing. Noninvasive assessment of FFR via a combination of computational fluid dynamics (CFD) and coronary CT angiography CCTA (the so-called FFRCT) has potential. Coronary computed tomographic angiography is a noninvasive test for diagnosis of anatomic coronary stenosis (i.e., narrowing of a blood vessel). A new analytical model of FFR from the general Bernoulli equation (conservation of energy) (FFRB) is simple and has potential. A collaborator group has recently developed a new analytical model to quantify pressure drop, and hence FFR, based on lesion dimensions (i.e., the cross-section area along the lesion and the length of lesion) and coronary flow, with no empirical parameters. The investigators hypothesize that this new model will allow quantification of FFR (FFRB) in a cohort of human patients with intermediate coronary stenosis. The study will compare FFRB with invasive FFR measurements from invasive coronary angiography (ICAG).