In a head-to-head comparison of fractional flow reserve (FFR) and intravenous ultrasound (IVUS) for guiding revascularization during percutaneous intervention (PCI), outcomes were noninferior at 2 years, but the approaches appear to have different strengths, according to results of the FLAVOUR trial.
For the primary composite outcome of death from any cause, myocardial infarction, or revascularization at 24 months, the approaches performed comparatively, but there were substantial differences in the number of revascularization procedures performed, reported Bon-Kwon Koo, MD, at the annual scientific sessions of the American College of Cardiology.
At 24 months, 8.1% of the FFR group and 8.5% of the IVUS group had a primary event. The 0.4% difference was not significantly different and fulfilled the definition of noninferiority (P = .015). When the components of the primary endpoint were compared along with rates of stroke, the rates were also similar and not significantly different.
However, the proportion of patients who received a stent (44.4% vs. 65.3%), the total number of stents per patient (0.6 vs. 0.9), and the total stent length per patient (16.5 vs. 25.2) were significantly lower (all P < .001) in the FFR group.
FLAVOUR (Fractional Flow Reserve And IVUS for Clinical Outcomes in Patients With Intermediate Stenosis) confirmed the investigators’ hypothesis that an FFR-guided strategy for intermediate coronary stenosis is noninferior to IVUS for outcomes. In addition, patient-reported angina outcomes on the Seattle Angina Questionnaire were nearly identical across domains, including angina frequency, physical limitations, and treatment satisfaction.
FFR vs. IVUS differences revealed
However, the more important value of this study might its role in showing how the two approaches differ in ways unrelated to the primary outcome, according to Dr. Koo, chair of cardiology at Seoul (South Korea) National University Hospital, as well as several experts that commented on the results.
Most notably, the fact that FFR-guided PCI provides similar outcomes at 2 years even though it was associated with a substantially reduced rate of revascularizations is telling about its role relative to IVUS.
“These data confirm how a lot of us are already approaching this,” said an ACC-invited expert, Frederick G. Welt, MD, director of the cardiac catheterization at the University of Utah, Salt Lake City. “FFR should be used to decide who should get an intervention, and IVUS should be use to optimize the intervention.”
Dr. Koo explained that FFR is an invasive tool that provides a physiological assessment of the degree to which a stenosis is causing ischemia. IVUS is a tool that permits visualization and measurement of plaque severity and characteristics to better optimize PCI. They can both help guide PCI, but they are not necessarily competing strategies. Often, the information they provide is complementary.
In this multicenter trial conducted at 18 centers in Korea and China, 1,682 candidates with de novo stenoses of intermediate severity, defined as 40%-70%, were randomized to FFR- or IVUS-guided PCI. At 24 months, outcomes could be assessed in 832 of the FFR patients and 836 of the IVUS patients, which represented more than 99% of both groups.
In the study, the indications for stent placement were predefined for the FFR-guided and IVUS-guided approaches. The criteria to define optimal outcomes post PCI were also predefined. For FFR, this included a postprocedure value of at least 0.88. For IVUS, the definition of optimal outcome included a plaque burden of 55% or less at the stent edge and a minimal stent area of at least 5.5 mm2.
The primary outcome for those with optimal versus suboptimal FFR-guided PCI were similar at all time points. For those with an optimal post-PCI result, the event rate was only slightly higher for those with an optimal relative to a suboptimal result (12.3% vs. 11.8%).