The Drift-Reduction for Improved FFR Using Fiberoptic Technology (DRIFT) Study

Inclusion Criteria: * Male or female subjects, \>18 years of age. * Patients with stable angina, unstable angina or non-ST segment elevation myocardial infarction (if the LAD lesion is the non-culprit lesion) and in whom an intermediate proximal LAD de novo stenosis (30-80%) with TIMI flow 3 has been identified on angiography. Note: Patients with multi-vessel disease can be enrolled. * Patients have had fractional flow reserve (FFR) and optical coherence tomography (OCT) of the LAD with the OpSens FFR system as part of their routine evaluation as standard of care procedure. * Provides written, informed consent and HIPAA consent to use the data in a clinical study. Exclusion Criteria: (General exclusion criteria) * Patients presented with NSTEMI with the LAD involved as the culprit lesion * Any ST-elevation myocardial infarction within the past 30 days. * Hemodynamic instability requiring vasopressor or mechanical circulatory support. * Prior heart transplant. * Known left ventricular ejection fraction ≤40%. * LAD supplying akinetic or severely hypokinetic territories if already known based on prior imaging. * Patient is enrolled in another clinical study that may impact the results of this study. * FFR not acquired per instructions for the OpSens Wire. * LAD Lesion not assessed with OCT. (Angiographic exclusion criteria) * Thrombolysis in Myocardial Infarction (TIMI) grade 2 or lower at baseline angiography. * Target lesion involves left main (stenosis \>50%). * Previous percutaneous coronary intervention (PCI) with stent in LAD or left main trunk. * Presence of chronic total occlusion in any vessel. * Presence of a side branch≥2.75 mm with ≥70% stenosis in the LAD. * Bifurcation lesion that resulted in the stent implantation of a side branch.