FUnctional diagnoSIs of corONary Stenosis (FUSION)

Inclusion Criteria:

* Age ≥18 years
* Patient provides written informed consent
* Scheduled for clinically indicated coronary catheterization with the intent to perform physiologic assessment to guide physician clinical course (in lesions with visual % diameter stenosis 40-90%), if clinically indicated
* Subject is undergoing invasive FFR with Adenosine (high-dose intra-coronary (IC) \[200 μg for the left and or 100 μg for the right coronary artery\] or 140 μg/kg/min for intravenous (IV)) used as hyperemic stimulus
* Clinical presentation with or history of stable angina, unstable angina, or silent ischemia (defined as abnormal stress test or abnormal invasive physiology assessment) that has led to the procedure

General Exclusion Criteria:

* Prior history of myocardial infarction (MI) in the target vessel
* Presence of acute ST Elevation Myocardial Infarction (STEMI)
* Culprit vessel of Non-ST Elevation Myocardial Infarction (NSTEMI)
* TIMI flow \< Grade 3 at baseline or visible thrombus
* Prior history of coronary artery bypass grafting (CABG)
* Prior heart transplant
* Severe valvular heart disease or history of valve repair or replacement
* Prior history of PCI with stent in target vessel, or target vessel involves in-stent restenosis.
* Target coronary vessel is supplied by major collaterals or is supplying major collaterals to a CTO (chronic total occlusion)
* CTO in the target vessel
* Severe diffuse disease observed in target vessel defined as the presence of diffuse, serial gross luminal irregularities present in the majority of the coronary tree
* Presence of myocardial bridge (MB), regardless of vessel location
* Contraindication for FFR examination or administration of vasodilators
* Known LVEF ≤45%
* Target lesion involves Left Main coronary artery or ostial right coronary artery
* Known renal insufficiency (eGFR \< 30 ml/kg/m\^2 or serum creatinine ≥ 2.5 mg/dL) unless patient is on dialysis
* Heart Failure NYHA Class III or IV
* Subject is pregnant (For a female subject of childbearing potential, a pregnancy test must be performed within 14 days (≤14 days) prior to the index procedure per site standard test)
* Subject has or had active COVID-19 symptoms and/or a positive test result within the prior 2 months
* Participation in another clinical study of an investigational drug or device
* Presence of aneurysm in the target vessel

Imaging and Pressure Tracing Exclusion Criteria:

* Artifact in pre-PCI OCT for the target lesion or in the event of multiple target lesions, artifact in pre-PCI OCT for ALL target lesions
* Target lesion requires any preparation (including but not limited to balloon dilatation, atherectomy, etc.) prior to pre-PCI OCT and physiology measurement, or in case of multiple target lesions, ALL target lesions require-any preparation (including but not limited to balloon dilatation, atherectomy, etc.) prior to pre-PCI OCT and physiology measurement
* Severe vessel tortuosity or calcification in the target vessel such that it is unlikely that the OCT catheter can be delivered
* Target lesion not imaged by OCT or in the event of multiple target lesions, ALL target lesions not imaged by OCT
* Pressure drift of \> 0.03; i.e. Pd and Pa ratio value \< 0.97 or \> 1.03, unless physiology measurements are repeated after re-equalization
* Target lesion or significant CAD beyond 60mm from coronary ostium; i.e. not able to clearly image and capture all disease segment with OCT in 1 run
* Incorrectly done or unsuccessful catheter purge and/or contrast flush
* Presence of plaque rupture and/or intravascular hematoma in target vessel (visual % diameter stenosis ≥ 40%)
* Inability to receive intracoronary nitroglycerin prior to OCT or FFR
* Use of flush media other than radiographic contrast