Impact of Epicardial plaQUe composition and geometry on coronary hemodynamics and flow (iEquate)

Consent for the research project will be obtained before undergoing the coronary angiogram. The angiogram is administered outside the study (meaning that the patient has a clinical indication for the angiogram, including angina). The angiogram is performed by a cardiologist and the associated cardiology team, who assess the results. A diagnostic angiogram usually takes between 15-20 minutes. Patients who are subsequently identified to have moderate (50-75%) stenosis angiographically undergo invasive hemodynamic assessments using 0.014 inch pressure wire. This is performed as part of routine best clinical practice to determine need for percutaneous coronary intervention, using the hospital protocol for pressure wire assessments, and occurs immediately following the diagnostic angiogram. This is performed by the interventional cardiologist or the interventional cardiology fellow. This involves FFR (Fractional Flow Reserve) and iFR (instantaneous wave-free ratio) which can be performed using the same wire, without the need for re-instrumentation of the coronary artery. The standard procedural protocol would be applied, with pharmacological stress or exercise-induced stress (using an Ergometer) used to stimulate hyperaemia within the artery in order to obtain pressure wire assessments. All hemodynamic values will be recorded. In total, invasive hemodynamic assessments add no more than 15 minutes to the diagnostic angiogram. If a patient has consented to the research project before undergoing the coronary angiogram, and are found to have moderate stenosis, an OCT catheter will be passed over the coronary wire to obtain intra-vascular imaging and plaque composition assessment. On average, this adds 3-4 minutes to the standard hemodynamic assessments. Following the procedure, patients are recovered for a total of 4 hours with cardiac monitoring, as per post-procedural protocol. No additional requirements are necessary for the recovery as a result of participation in this study. Data will be collected on the minimal luminal area (MLA), plaque geometry (irregularity/angulation/length), degree of calcification, fibroatheroma, necrotic core, and lipid content. These variables will be examined in terms of relationship to the pressure wire value. If the lesion meets hemodynamic significance (i.e. iFR value less than or equal to 0.89 or FFR value less than or equal to 0.8). Percutaneous Coronary Intervention (PCI) may be performed if clinically suitable as per usual clinical practice. Phone call follow up will be performed at 1 month following recruitment, and medical record follow up will be performed at 1 year, to assess for target lesion failure (TLF). Computational fluid dynamics (CFD) will be performed to simulate coronary flow using software to reconstruct three dimensional reconstructions of the coronary artery assessed using the angiographic and OCT images and hemodynamic data obtained during the procedure. Key computational parameters such as wall shear stress (WSS) and helicity will be calculated, and linked with both pressure wire observations, and 1 year outcomes of target lesion failure. All involved medical staff will be briefed by a member of the research team, and data logged in a secure password-encrypted database.