 Patients with borderline 50 - 70 or positive CCTA 70 stenosis readings will undergo ICA with invasive FFR measurement in accordance with accepted guidelines and established practice standard. Those patients with invasively measured FFR0.8 and with vessel diameter of 2mm, or those who require revascularizations based on invasively estimated stenosis severity for patients who are totally obstructed will be considered to have flow-limiting obstructive CAD, while the rest will be considered to have non-flow limiting obstructive CAD if also 50 stenosis on ICA. If stenosis severity turns out to be 50 after ICA, these patients will have been shown to have non-obstructive CAD. Figure 1. Patients with 30 to 49 obstructive stenosis by CCTA standards and with positive CT-FFR, will also undergo invasive FFR and follow the protocol for those with 50 obstruction. Patients with 0 to 49 obstructive disease and negative CT-FFR will be referred to optimal follow up care only. 