The use of invasive coronary physiology-guided decision making such as fractional flow reserve (FFR) has been supported by numerous clinical trials and such practice is endorsed by ACC/AHA and ESC/EACTS guidelines.
Nevertheless, FFR remains underutilized in real-world practice, most likely due to use of additional resources including pressure wire, hyperemic agents, or prolonged procedural time.
To overcome these limitations, recent advances in angiography-derived coronary physiology has shown great promise. Such functional angiogram may allow wire-free assessment of physiological significance of epicardial coronary stenosis based on computational or mathematical calculation.
Much evidence has attested to the precise diagnostic accuracy of various angiography-derived FFR platforms. The U.S. Food and Drug Administration (FDA) has since approved the use of Quantitative Flow Ratio, Virtual FFR, and FFRangio.
William Fearon, MD (Stanford University School of Medicine, California) presented results from the FAST -FFR study, for which he was the principle investigator, and on angiography-derived coronary physiology at a session held during TCTAP 2021 Virtual.
Angiography-derived coronary physiology uses a reconstructed three-dimensional model of the coronary vessel and computational flow dynamics or mathematical calculation to derive hyperemic pressure gradient across the stenosis and ultimately angiography-derived FFR in the target vessel. Fearon also introduced the pivotal studies of QFR, vFFR, and FFRangio.
The Functional Diagnostic Accuracy of Quantitative Flow Ratio in Online Assessment of Coronary Stenosis II China study- dubbed the FAVOR II China study (NCT03191708) - was a prospective, multicenter trial that enrolled 308 patients and evaluated diagnostic accuracy of QFR to predict wire-based FFR.
QFR showed excellent correlation with wire-based FFR (r=0.857). Sensitivity, specificity, and diagnostic accuracy of QFR were 95%, 92%, and 93%, respectively, for wire-based FFR ≤0.80.
The FAST (Fast Assessment of STenosis severity) study was an observational, retrospective, single-center cohort study that evaluated 100 patients. Correlation of vFFR with wire-based FFR was excellent (r=0.89) and area under curve of vFFR was 0.93 to predict wire-based FFR ≤0.80.
FAST-FFR study was a prospective, multicenter, international trial with the primary objective of comparing the accuracy of on-site FFRangio with wire-based FFR. A total of 301 patients (319 vessels) were included in the final study analysis population. Co-primary endpoints were the sensitivity and specificity of FFRangio for predicting wire-based FFR≤0.80. Per-vessel sensitivity and specificity were 95% and 91%, respectively. The diagnostic accuracy of FFRangio was 92% overall.
“These techniques are quite accurate and may be able to replace wire-based techniques.” Fearon said.
He also shared two cases - involving an 86-year old woman treated with TAVR and PCI for LAD lesions and atypical chest pain, and a 77-year old man who presented progressive exertional chest discomfort - that supported the practical role of angiography-derived FFR in real world practice.
In the first case, angiography showed patent LAD stent, intermediate stenoses in obtuse marginal branch and posterior descending artery. FFRangio in obtuse marginal branch was 0.88 and wire-based FFR was 0.83. FFRangio in posterior descending artery was 0.86 which was well correlated with wire-based FFR of 0.81.
In the second case, myocardial perfusion scan showed no myocardial ischemia. However, he was referred for coronary angiography based on persistent symptom despite medical therapy. LAD showed significant coronary calcification with mild to moderate stenosis in mid-LAD. Interestingly, FFRangio in LAD was 0.75 and wire-based FFR was also significant (0.64).
”We look forward to results from the FAVOR III China trial that completed recruitment in January last year,” Fearon said. “The trial will compare one-year clinical outcome of 3,828 patients who were randomly allocated into either QFR-guided strategy versus angiography-guided strategy.”
Fearon then briefly introduced a recent study of angiography-derived index of microcirculatory resistance (IMR) that showed reasonable correlation (r=0.746) and area under curve (AUC) of 0.919 to predict wire-based IMR.
He summarized his talk by highlighting the importance of generating more clinical data of angiography-derived physiology in a real world setting, especially for clinical outcomes to reassure whether the angiography-derived physiology can replace conventional wire-based physiology.
“The next key step is to generate more clinical data validating these techniques in the real-world setting and against clinical outcome,” Fearon said. “The data will most likely reassure us that these techniques can replace wire-based physiology.”
Editor: Joo Myung Lee, MD (Samsung Medical Center, Sungkyunkwan University School of Medicine, Korea (Republic of))