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FFR, iFR results linked to MACE risk in deferred lesions
The future risk for MACE was significantly increased in patients with lesions with abnormal results in both fractional flow reserve and instantaneous wave-free ratio, according to a substudy of the 3V FFR-FRIENDS study.
For this analysis, the researchers grouped 821 deferred lesions from 372 patients with available FFR and instantaneous wave-free ratio (iFR) according to cutpoints. The first group included normal lesions with FFR greater than 0.8 and iFR greater than 0.89; the second included lesions with high FFR (> 0.8) and low iFR ( 0.89); the third group included lesions with low FFR ( 0.8) and high iFR (> 0.89); and the fourth group included abnormal lesions that had both FFR of 0.8 or lower and iFR of 0.89 or lower.
FFR and iFR correlated significantly, with only 8.8% of lesions having discordant results between the two measurements, the researchers noted.
The primary outcome was MACE, defined as a composite of cardiac death, MI and ischemia-driven revascularization, at 2 years.
Results showed that MACE was increased at 2 years in deferred lesions with low FFR or low iFR, as compared with high FFR (7.2% vs. 2.4%; P < .001) or high iFR (8.1% vs. 2.4%; P < .001). As continuous values, there were significant associations between MACE and FFR (HR = 0.57; 95% CI, 0.337-0.963) and iFR (HR = 0.35; 95% CI, 0.217-0.567).
FFR and iFR also appeared comparable in comparison of their discriminant ability (C-index, 0.677 vs. 0.685; P = 0.857), according to the data.
When compared with lesions with both high FFR and high iFR results, only lesions with both low FFR and low iFR had an increased risk for MACE (HR = 7.708; 95% CI, 2.621-22.667). There were no significant differences in rates of MACE between groups with discordant iFR and FFR results.
“These results may suggest the importance of comprehensive evaluation rather than choosing only one index to properly select the optimal target for revascularization,” the researchers wrote. “Further study is warranted to investigate the clinical outcomes of those discordant lesions according to treatment strategy (deferral vs. revascularization), compared with concordant abnormal lesions.”
These findings raise several questions, including which measurement to use or whether both FFR and iFR are necessary when evaluating ischemia, Arnold H. Seto, MD, MPA, FSCAI, FACC, from the University of California, Irvine in Long Beach, wrote in an accompanying editorial. He noted that neither test is perfect.
“There is no threshold value in nature for ischemia, FFR or iFR; rather there is a continuum of risk, of probabilistic potential of causing ischemia,” he wrote.
Ultimately, a physician’s choice as to which test to use is likely dependent on a number of factors, such as patient characteristics and workflow, according to Seto.
“A single test will be sufficiently positive or negative to make a decision in most cases, but in borderline cases both might be helpful to justify a particular action,” he wrote. “Either way, after multiple clinical studies, it is increasingly clear that iFR works, and appears to work as well as FFR, to the best of our current knowledge.” – by Melissa Foster
Disclosure: Bon-Kwon Koo, MD, PhD, reports receiving an international research grant from St. Jude Medical. All other authors report no relevant financial disclosures. Seto reports he has received research grants and speaking honoraria from Philips Volcano and Acist.