William F. Fearon
SAN DIEGO — Fractional flow reserve derived from coronary angiography is comparable to conventional pressure wire-derived FFR for physiologic assessment of coronary stenoses, according to new findings from the FAST-FFR trial.
“FFR derived from routine coronary angiography had a very high sensitivity, specificity and diagnostic accuracy — all of which were greater than 90% for predicting the reference standard of coronary pressure wire-derived FFR. [Angiography-derived FFR] and FFR remain tightly correlated over the range of FFR values and [angiography-derived FFR] was successfully measured in almost all cases included [in the trial],” William F. Fearon, MD, professor of medicine and director of interventional cardiology at Stanford University School of Medicine, said at TCT 2018.
Among the 301 patients and 319 vessels included in the FAST-FFR trial, the mean FFR result was 0.81. Forty-three percent had FFR values of 0.8 or lower and a majority fell into the range of intermediate stenosis — a population that is representative of patients in whom FFR is usually measured, Fearon said.
In addition to the high sensitivity (93.5%; 95% CI, 87.8-96.6) and specificity (91.2%; 95% CI, 86-94.6) of angiography-derived FFR, diagnostic accuracy (92.2%; 95% CI, 88.7-94.8), positive predictive value (89%; 95% CI, 82.6-93.2) and negative predictive value were also high (94.8%; 95% CI, 90.3-97.3). All findings were well above the predefined performance goals, according to Fearon.
“If you just focus on FFR values around the cut point of 0.8, you continue to have very high diagnostic characteristics, with sensitivity, specificity and diagnostic accuracy in the high 80% range,” Fearon said, noting that correlation between pressure wire-derived FFR and angiography-derived FFR was “excellent” without any bias throughout the whole range of FFR values.
There were 24 discordant cases, but there were no significant differences between groups in terms of clinical characteristics, he said.
Despite evidence demonstrating the benefits of physiologic assessment, FFR utilization remains lower than expected due to a number of issues, including the extra time needed to perform FFR, wire handling characteristics, pressure wire drift, the need for hyperemia and the expense, according to Fearon. For these reasons, he noted, a technique for deriving FFR without the need for a pressure wire or hyperemic agent would be advantageous.
“[Angiography-derived FFR] may provide an easier and potentially faster method for performing physiology-guided assessment of the overall coronary angiogram, with similar accuracy to the reference standard of coronary pressure wire-based FFR. This may translate to a greater percentage of patients undergoing physiologic guidance for revascularization decisions and, ultimately, improve long-term outcomes,” Fearon said.
Coronary angiography-derived FFR involves obtaining optimal projections of the vessel of interest. A 3D reconstruction of the coronary arterial system is created, the stenoses along the vessels are assessed and, using the model of estimating resistance across the stenoses in the branches, the flow in the presence of the stenosis is then calculated and compared with the flow in the theoretical absence of the stenosis. Then, angiography-derived FFR is obtained, Fearon said.
Ten centers in the United States, Europe and Israel participated in FAST-FFR. Coronary angiography was performed at each site according to standard of care with any commercially available system. Angiography-derived FFR was performed by obtaining at least three Digital Imaging and Communications in Medicine (DICOM) videos of the vessel of interest, which were transferred immediately to the angiography-derived FFR consult. A hospital operator then calculated the angiography-derived FFR masked to the pressure wire-derived FFR and the result was sent to the core lab.
Patients with stable angina, unstable angina or non-STEMI ACS undergoing coronary angiography with coronary pressure wire-derived FFR measurement of a coronary stenosis were included in the trial. Clinical exclusion criteria included STEMI within the past 12 months, prior CABG, valve surgery or heart transplantation, severe aortic stenosis or left ventricular ejection fraction of 45% or less. Angiographic exclusion criteria included left main stenosis greater than 50%, chronic total occlusion, less than TIMI 3 flow in the target vessel, in-stent restenosis or recent stent placement in the target vessel, severe disease or a target vessel containing collaterals.
The need to study the technology in these excluded patient subsets is necessary before drawing further conclusions, Fearon said. Additionally, the researchers did not specifically assess the time needed to calculate angiography-derived FFR in comparison with pressure wire-derived FFR, which was a limitation of the study. – by Melissa Foster
Fearon WF, et al. Late-Breaking Clinical Science 2, Co-Sponsored by The European Heart Journal. Presented at: TCT Scientific Symposium; Sept. 21-25, 2018; San Diego.
Fearon WF, et al. Circulation. 2018;doi:10.1161/CIRCULATIONAHA.118.037350.
Disclosure: Fearon reports he receives institutional research support from Abbott, Medtronic and CathWorks; he is a consultant for Boston Scientific; and he has minor stock options with HeartFlow.