These international studies, which involved senior researchers from RDM and Oxford University Hospitals (OUH), looked at different ways of guiding coronary revascularisation - a treatment aimed at restoring blood flow to the heart.
The studies were presented at the American Cardiology Conference earlier this year and published simultaneously in the world's leading medical journal, New England Journal of Medicine.
Two of the trials, the OPTIMAL study and IVUS-CHIP, assessed intravascular ultrasound (IVUS), a technique that uses a miniature ultrasound probe inside the blood vessel to give a more detailed picture of the artery with the aim of selecting the right size stent and positioning it more precisely. Both studies found that routine IVUS guidance did not lead to better overall outcomes for patients than standard angiography, the imaging technique currently used during percutaneous coronary intervention (PCI), a procedure in which a stent is inserted to help keep the artery open.
In the OPTIMAL study, 806 patients with left main coronary artery disease who had not previously had bypass surgery were randomly assigned to have PCI guided either by IVUS or by angiography alone. The left main coronary artery is the most important coronary artery as it supplies blood to most of the heart muscle. After a follow-up of around three years, rates of stroke, heart attack repeat treatment to restore blood flow or death were similar in the two groups, occurring in 34% of patients in the IVUS-guided group and 31% of those in the angiography-guided group.
The IVUS-CHIP study looked at over 2,000 patients undergoing complex, high-risk PCI - procedures involving more difficult artery narrowing. Again, IVUS guidance did not significantly reduce the main outcome, known as target-vessel failure, when serious problems affect the treated artery. Target-vessel failure occurred in 14% of patients in the IVUS group and 11% in the angiography group after an average follow-up of 19 months.
Adrian Banning, Professor of Interventional Cardiology at RDM and OUH Director of Research and Development, was Chief Investigator on the OPTIMAL trial and Principal Investigator in Oxford for the IVUS CHIP trial. He said: 'After nearly three years of the OPTIMAL study, we found that IVUS guidance did not reduce the risk of stroke, heart attack, further procedures or death compared with angiography alone. Our findings may challenge guidance that IVUS should always be used for complex PCI. The IVUS CHIP trial, which was carried out in a number of busy hospitals across Europe, found that using IVUS imaging routinely during complex, high-risk coronary stent procedures offered limited extra benefit. It did not reduce the risk of target-vessel failure compared with standard angiography guidance. The risk of complication was similar with both approaches.'
A third study, FAST III, looked at fractional flow reserve (FFR), which measures to what extent a narrowing in the artery is actually limiting blood flow. The study compared standard FFR with vessel fractional flow reserve (vFFR). In the standard method, a small pressure wire is passed through the blockage in the artery to measure how much it has reduced blood flow; vFFR estimates the same information using standard X-ray imaging and computer modelling to create a three-dimensional image of the artery, without the need for the pressure wire. FAST III included more than 2,000 participants with moderate coronary lesions, or narrowing of the arteries. After one year, the proportion of patients who had experienced death, heart attack or any repeat revascularisation was 7.5% in both the vFFR and FFR groups.
Dr Giovanni De Maria, OUH Consultant Interventional Cardiologist and Honorary Senior Clinical Lecturer of Interventional Cardiology at RDM, was the Principal Investigator in Oxford for both the FAST III and OPTIMAL trials. He said: 'Within the parameters set by the trial, vFFR was found to be just as safe and effective as FFR when looking at our key outcomes; vFFR led to more patients having procedures, but outcomes were similar. This could potentially be significant because they suggest a wire-free method could offer similar outcomes to the established pressure-wire approach, potentially making assessment simpler and more comfortable for patients.'
Professor Banning concluded: 'These studies show how NHS teams can deliver cutting edge, practice changing research that ultimately improves the outcomes for our patients in Oxford. It demonstrates the powerful synergy of NHS researchers working closely with the University of Oxford and the NIHR Biomedical Research Centre: Oxford.'