SAN DIEGO – A less-invasive way to measure fractional flow reserve using angiography had a sensitivity of 94% and specificity of 91%, compared with standard wire-based techniques, according to a report at the Transcatheter Cardiovascular Therapeutics annual meeting.
The method may provide an easier and potentially faster method for performing physiology-guided assessment of the overall coronary angiogram than with coronary pressure wire–based FFR, William Fearon, MD, said in presenting results of the FAST-FFR trial.
The added bonus of the FFRangio system, from the Israeli company CathWorks, is that it automatically produces a 3-D reconstruction of the entire coronary tree and can calculate FFR values for all occlusions. It requires high-quality angiograms, which are transferred to a proprietary counsel; the system estimates resistance and flow across stenoses using an algorithm. After a few cases, the process takes less than 5 minutes. CathWorks is working on Food and Drug Administration clearance, Dr. Fearon reported.
Several other companies are also developing noninvasive ways to measure FFR, the pressure gradient across lesions. It helps clinicians make the call on revascularization, since angiograms can be deceiving; occlusions that look bad might not really be causing a problem, and vice-versa.
FFR is recommended in assessment guidelines, but it’s not used much. The problem is that traditional measurement requires threading wires down coronary arteries; the technique is a bit risky and takes time and training. It also has to be repeated for each lesion.
The new system “has the potential to eventually replace wire-based FFR measurement and substantially increase physiologic coronary lesion assessment in the catheterization laboratory, thereby leading to improved patient outcomes,” said Dr. Fearon, professor of cardiology at Stanford (Calif.) University.
He said that he thought FFRangio could change practice, and several panelists agreed. “This is a real advance in the field. The use of FFR is not as great as it should be. I hope this will improve the ability of the assessor to identify ischemic lesions. I think that’s what’s going to happen. This is going to drive us forward,” said Mark Reisman, MD, head of cardiology and director of the Center for Emerging Cardiovascular Therapies at the University of Washington, Seattle.
The FAST-FFR (FFRangio Accuracy versus Standard FFR) study was conducted at 10 centers in the United States, Europe, and Israel; FFRangio was used to obtain FFRs in 319 vessels among 301 patients; the results were checked against FFR measured by wire. FFRangio operators were blinded to wire results.
The mean FFR was 0.81, and 43% of vessels had an FFR of 0.80 or less, signaling a possible abnormality. The diagnostic accuracy of FFRangio against wire measurement was 92%, and 87% when only gray-zone values between 0.75-0.85 were considered. Correlation with wire measurements was good (r = 0.80; P less than 0.001). Mismatches with the wire were more likely in the right coronary artery. The results were published online at the time of the presentation at TCT, sponsored by the Cardiovascular Research Foundation (Circulation. 2018 Sept 24. doi: 10.1161/circulationaha.118.037350).
“The main issue with this is that we need to do optimal angiographies. We should be doing them on a routine basis, but oftentimes, cardiologists want to be quick; they get lazy. But you do need to fill the entire vessel with contrast,” Dr. Fearon said.
“One of the nice things is you can rotate” the 3-D coronary artery tree reconstruction. “You can get a better idea of the relationship between the lesion and side branches, the length of the lesion, and a lot of additional information you don’t have on the angiogram [alone]. Then, you can pull back the cursor and measure FFR all along the vessel and different branches, all based on one angiography,” he said.
The majority of patients in the study were overweight or obese with complex coronary anatomy, as in daily practice. The investigation was limited to lesions amenable to wire measurement, so it didn’t include left main disease, low ejection fraction, and in-stent restenosis, although assessment may be possible.
Dr. Fearon didn’t know how much FFRangio will cost if it’s cleared or how CathWorks will be made available.
The work was funded by CathWorks. Dr. Fearon disclosed institutional research support from the company. One of the investigators was a cofounder of the company, with shares and intellectual property rights. The TCT meeting is sponsored by the Cardiovascular Research Foundation.