FFR Not Better, Just Different From IVUS for PCI

Ted Bosworth

April 14, 2022

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 be its role in showing how the two approaches differ in ways unrelated to the primary outcome, according to 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 used to optimize the intervention."

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 was 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%).

Suboptimal IVUS Differs From Suboptimal FFR

In contrast, the event rates over the course of follow-up were consistently higher among those with a suboptimal relative to an optimal IVUS-guided PCI. At the end of 2 years, the numerically greater rate of events among those with a suboptimal IVUS-guided PCI was not significant (9.8% vs. 8.5%; P = .212), but the gap was larger than that seen with FFR-guided PCI.

FFR-guided and IVUS-guided PCI performed similarly for the primary outcome across numerous stratifications. These included age older or younger than 65 years, male or female sex, presence or absence of multivessel disease, and presence of diabetes. They were also similar for those with acute coronary syndrome (ACS) as an indication for PCI, which accounted for about 30% of patients, relative to those without ACS.

"I would say that at least some interventionalists in the U.S. would be uncomfortable using FFR in ACS patients," said Welt, pointing out a potential difference between how these tools are used to guide PCI. Still, because "there are not a lot of data to compare these technologies," he expressed appreciation for a study looking at these tools side-by-side.

A similar point was made by Ajay Kirtane, MD, director of Cardiac Catheterization Laboratories at New York–Presbyterian/Columbia University Irving Medical Center. With the slightly lower rates of primary events in those treated optimally according to IVUS relative to those treated optimally by FFR (8.5% vs. 12.3%), he suggested IVUS appears better for evaluating the physiology of the stenosis.

Kirtane pointed out that two-thirds of the lesions were left behind in those guided by FFR versus only about half of the lesions when PCI was guided by IVUS, yet outcomes were similar. He indicated that the data support current practice in which FFR is most commonly used to select PCI patients with intermediate disease for stent placement.

Koo has financial relationships with Abbott, Boston Scientific, and Philips Volcano. Welt has financial relationships with Medtronic and Xenter. Kirtane has financial relationships with Abbott, Amgen, Boston Scientific, Chiesi, Cardiovascular Systems Incorporate, Medtronic, Philips/Spectranetics, Recor Medical, and Regeneron. The study received a research grant from Boston Scientific.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.