Justin E. Davies, MD, PhD, of Imperial College London, discussed the future of coronary physiology imaging, the DEFINE-GPS study, and their consequences for percutaneous coronary interventions (PCI), during his presentation Saturday at CRT Virtual 2021.
“I think there’s a chasm building,” Davies said, between “blind PCI,” meaning angiography-guided PCI, and “smart PCI,” meaning PCI guided and facilitated by the latest medical devices and technology. He argued that coronary physiology imaging and utilizing instantaneous free-wave ratio (iFR) measurements could serve as a bridge between the two approaches.
In recent years, clinical trials have shown that physiology-based methods have enabled physicians to make better-informed decisions and allow for better patient outcomes.
Davies pointed to Uppsala University’s iFR-SWEDEHEART study, a randomized, registry-based clinical trial with an enrollment of 2,037 patients at centers across Scandinavia, which showed that the outcomes of patients who underwent iFR were “almost identical” to those who underwent fractional flow reserve (FFR). Davies also highlighted Imperial College London’s DEFINE-FLAIR clinical trial, which found that “clinical outcomes were identical whether you used an iFR or FFR approach.”
Both of these studies found that an iFR approach had a reduced procedure time and cost and showed no increase in major adverse cardiac events (MACE) when compared to an FFR approach. Results from the international, multicenter iFR GRADIENT clinical trial, published in 2018 in the Journal of the American College of Cardiology, found that the iFR pullback technique predicted the outcomes of PCIs with a “high degree of accuracy.” IFR pullback altered procedural planning in more than one-third of patients.
One of the biggest components of an iFR approach is its focus on lesion-level ischemia rather than vessel-level ischemia. This allows for a more patient-specific line of treatment. One step further, Davies said, is the ability to co-register a patient’s physiology data onto an angiogram image almost in real-time.
Using case studies, Davies showcased the interface of Philips Volcano’s precision-guided therapy software, equipped with a dedicated iFR workflow, which has 3D-tracking capabilities and a calibrated pressure gradient. The system uses yellow dots to represent units of iFR.
“You can map on your physiology with your angiogram imaging and you can identify areas of focal disease,” Davies explained, noting that the software can reveal the concentration of disease by the amount of yellow dots it overlays in a specific area. Physicians can also use the device to simulate the drop of iFR and predict the effects of a procedure.
The DEFINE-GPS study, announced in February 2020, is a randomized, multicenter, prospective trial that seeks to build off of the data from the decade’s previous studies about iFR. Sponsored by Philips Clinical & Medical Affairs Global, with an estimated patient enrollment of more than 3,000 patients, the study aims to compare angiography-guided PCI to an iFR co-registration approach using the SyncVision co-registration system.
The study, Davies said, is a “ way to measure the field’s progress with physiological tools.”
“I think the most important thing this moves us on in the field,” Davies added, “is really moving away from vessel level ischemia as being that kind of gold standard, to perhaps one where we’re looking [at a] more patient-specific and lesion level assessment tool with a point of care technique which enables us to further iterate and improve our PCI.”
Other presenters included Jonathon Leipsic, MD, of St. Paul's Hospital, Vancouver, British Columbia, who discussed how computed tomography, coupled with physiology, can reduce rates of incomplete revascularization, and Andrew SP Sharp, MD, of University Hospital of Wales, who gave a rationale for the DEFINE-GPS study. Sharp presented on the conclusions from the previous DEFINE PCI clinical trial and detailed some case studies that involved the use of iFR.
CRT 2021 Virtual takes place Fridays and Saturdays through April 24. On-demand content from the meeting is available here.