October 16, 2020

Findings Reported From DEFINE-FLOW Study of Deferral of PCI in FFR-Abnormal Lesions With Preserved Coronary Flow Reserve

October 16, 2020—A new observational study of deferred lesions following combined fractional flow reserve (FFR) and coronary flow reserve (CFR) assessments found that untreated vessels with abnormal FFR but intact CFR do not have noninferior outcomes compared to those with an FFR > 0.8 and a CFR ≥ 2.0 when treated medically.

The background of these findings is that the role for invasive CFR assessment remains unclear since FFR has become a reference standard guiding decisions for revascularization. Although observational data from invasive and noninvasive tools has indicated that lesions with intact CFR do well, few of these studies simultaneously assessed FFR. Therefore, investigators designed and conducted the DEFINE-FLOW study to address the limitations of the current literature.

Nils Johnson, MD, presented the DEFINE-FLOW results at TCT Connect, the 32nd annual Transcatheter Cardiovascular Therapeutics scientific symposium of the Cardiovascular Research Foundation held online October 14-18, 2020.

According to the TCT Connect press release, the DEFINE-FLOW investigators enrolled 455 patients at 12 sites in six countries. Of these patients, 430 (533 lesions) were protocol-treated and followed for 2 years. Stable coronary lesions underwent simultaneous FFR and CFR measurement in at least duplicate with central core lab review of the tracings. Treatment followed the local measurements according to a uniform protocol whereby only lesions with both FFR ≤ 0.8 and CFR < 2.0 underwent percutaneous coronary intervention (PCI). All other combinations, including FFR ≤ 0.8 but intact CFR > 2.0, received initial medical therapy.

The study's primary endpoint was the composite of all-cause death, myocardial infarction, and revascularization at 2 years.

The investigators reported that rates of major adverse cardiovascular event (MACE) rates were 5.8% for FFR-/CFR-, 10.8% for FFR+/CFR-, 12.4% for FFR- /CFR+, and 14.4% for FFR+/CFR+ (after PCI). The difference of FFR+/CFR- compared to FFR-/CFR- was 5.0% (95% CI, -1.5% to +11.5%; P = .065 for noninferiority). Therefore, the study found that vessels with abnormal FFR ≤ 0.8 but intact CFR ≥ 2.0 did not have noninferior outcomes compared to FFR > 0.8 and CFR ≥ 2.0 when treated medically.

“Because the study was observational, it is not clear what the outcomes among FFR+/CFR- lesions would have been had they undergone PCI instead of medical therapy,” commented Dr. Johnson, in the TCT Connect announcement. “There were a number of limitations to this study such as few lesions with severe FFR/CFR as well as unblinded subjects and physicians. The limitations coupled with the results makes this a hypothesis-generating study that can help to further understand the role of invasive CFR and how to treat CFR/FFR discordance.”


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