The ACIST-FFR study is a prospective, open label, observational, multi-center study designed to assess the differences, if any, between FFR measured by the Navvus catheter and a commercially available 0.014-inch pressure guidewire (St. Jude Medical, Volcano, hereafter referred to as the PW) in subjects with coronary artery disease (CAD) undergoing coronary angiography. This will be accomplished by comparing the FFR measurement obtained with the ACIST Medical Systems RXi System and Navvus catheter with the FFR measurement obtained by using a PW within the same subject across the same target lesion at the same time.