Virtual Coronary Physiology: an Angiogram is All You Need

Plan of Investigation Several interacting workstreams will proceed in parallel in this observational, analytical, 36-month study between the University of Sheffield (UoS), Sheffield Teaching Hospitals NHS Foundation Trust (STH), and our collaborators at King's College London (KCL).

This protocol document outlines the methodology for clinical data collection from patients attending STH. These (fully anonymised) clinical data will then be used to validate and optimise the use of VIRTU by improving its accuracy and speed as well as developing a user-friendly interface. The development work will take place within the UoS and KCL, with no impact on NHS patient, staff or premises after the clinical data collection described below (these subsequent workstreams are detailed in Appendix 1).

Methodology (Workstream 1) Clinical data will be collected from the Cardiac Catheter Laboratory (CCL) at STH in a similar manner to which was performed in a pilot project. Therefore, the feasibility of recruitment targets and modelling techniques to be used in this study have already been demonstrated. In this current study, 100 patients with stable CAD of any pattern/severity, potentially suitable for PCI, will be recruited.

Potential participants will be identified by a member of the care team from pre-admission clinic lists in the cardiac catheter laboratory at the time of diagnostic angiography or referral from another Cardiologist. These patients will be sent a patient information sheet. If they are interested in finding out more about the study, the patients will meet with the Research Nurse or Doctor to discuss the project in more detail and ask questions. At the pre-admission clinic the Research Nurse or Doctor will take informed consent from those patients willing to participate and complete the study recruitment log and the Clinical Details section of the Data Collection Form.

The patients will then attend for their scheduled PCI at the Northern General Hospital at a later date (usually 2 -3 weeks after the pre-admission clinic). Details of the clinical procedure are below. During the PCI a member of the research team (Dr Gunn, Dr Morton, Dr Morris or Research Nurse) will record the arterial diagrams and procedure details on the second part of the anonymised Data Collection Form.

Clinical Procedure Selected patients will be asked to undergo cardiac magnetic resonance imaging before and after PCI, using a standardised protocol. All clinical and angiographic techniques are in routine NHS clinical practice. No experimental techniques will be used. Pre- and post procedure care will not alter from routine elective PCI care.

The PCI will proceed as normal where indicated, using best contemporary practice, including premedication. The study methods are in routine use for many patients undergoing PCI; and include rotational coronary angiography and pressure wire deployment to assess the physiological significance of lesions. This study merely requires that they be used systematically using standardised methodology.

Rotational coronary angiography will be recorded in standard single axis rotations (cranial and caudal for left coronary; plane PA for right coronary). An intravenous bolus of 200mcg GTN will be given prior to each run. They will be done on a breath hold, with a rapid hand injection of 10-20mL of contrast. Also, standard, single plane, orthogonal, carefully selected, angiograms will be recorded to guide the procedure. These will be performed at baseline and after stent deployment.

All major epicardial diseased vessels will be interrogated with a pressure wire (Volcano Corporation). An infusion of adenosine (140mcg/kg/min) will be set up and attached to the intravenous cannula in the hand/arm. The pressure wire will be calibrated against the guide catheter pressure, with the introducing needle removed. The wire will then be advanced across the lesion(s). A bolus of 200mcg GTN will be given and then the iv adenosine infusion started (repeated as necessary since adenosine has very short half life). When the pressures have stabilised, the baseline pressure and flow velocity will be recorded as the wire is withdrawn, while imaging, at 1cm/sec.

Stent implantation will proceed according to the clinical judgment of the operator, using both the angiographic appearance and the pressure gradient (Fractional Flow Reserve) across any lesions of interest as arbiters. Standard criteria will be used; namely a stenosis that appears to be >50% diameter stenosis in 2 orthogonal projections by eye (or >70% in one) and/or an FFR <0.80. The choice of stent will be at the discretion of the operator.

After stent deployment, the rotational angiograms and pressure wire pullback will be repeated, using the methods described above. In the case of multi-vessel disease, the pullback will be repeated for the 2nd and the 3rd vessels.