Coronary physiology and absolute coronary flow in severe aortic stenosis.

Study setting: This project will take place at MonashHeart, Monash Health. MonashHeart is a high volume transcatheter aortic valve replacement (TAVR) centre in Victoria and is an established academic cardiothoracic centre. MonashHeart is acknowledged as a leading site for research into coronary physiology and cardiac CT. Annually, over 200 aortic valve implantations (both TAVR and SAVR) and >3000 cardiac CTs are carried out at MonashHeart making recruitment targets achievable. Patient recruitment: Patients who are due to undergo aortic valve replacement, either TAVR or SAVR are referred for an invasive diagnostic coronary angiography as part of their routine clinical care and pre-procedural assessment. Potential participants will be identified from referrals to the Structural Heart Disease Service or from referring Cardiology Clinics based at the MonashHeart and Monash Health. For detailed inclusion and exclusion criteria, please refer to step 5: Key Inclusion criteria and Step 5: Key Exclusion criteria. Consent: Potential participants will be identified at the point of referral to the Structural Heart disease service, or other cardiac clinics. They will be provided with the Participant Information and Consent form (PICF) ahead of the coronary angiogram with ample opportunity to discuss the study with members of the research team. They will be informed of the voluntary nature of participation. Consenting will take place before the invasive coronary angiogram, which occurs as part of their routine clinical care. Cardiac catheterisation protocol: When the patients will present for their diagnostic angiogram, which is part of the standard clinical work-up prior to aortic valve intervention, we will assess the coronary physiology and the absolute coronary flow using a pressure and temperature sensing guide wire (Pressure Wire X, Abbott, USA) and RayFlow monorail catheter (Hexacath, France). The left main coronary artery will be engaged using a guiding catheter and a guidewire equipped with a pressure a temperature sensor (Pressure Wire X, Abbott, IL) is advanced into the left anterior descending artery (LAD). Resting and hyperaemic indices of coronary physiology are measured using intravenous adenosine infusion to achieve maximal hyperemia. A dedicated monorail catheter (Rayflow, Hexacath, Paris, France) is then advanced over the guidewire into the proximal segment of the LAD. A continuous infusion of normal saline is then infused through this catheter at rates of 15, 20, 25 and 30ml/min to produce a hyperaemic state. The absolute coronary flow measurements are recorded at the different flow rates. The measurements will be repeated in upto three arteries. Obtaining these measurements will add an additional 15minutes to the overall diagnostic angiogram. A member of the study team will oversee that the protocol is adhered to for all measurements. This will help understand the significance of concomitant coronary artery disease, which in turn will help guide future management strategies of the coronary artery disease.