Paris (FRONTLINE MEDICAL NEWS) – Fractional flow reserve is under study for a potential major application: guidance on percutaneous coronary intervention (PCI) optimization immediately after stent placement, Roberto Diletti, MD, said at the annual congress of the European Association of Percutaneous Cardiovascular Interventions.

He reported on preliminary results from the ongoing FFR-SEARCH study, a prospective registry of 1,000 patients who underwent measurement of fractional flow reserve (FFR) after completion of stenting of coronary lesions and whose angiographic results were deemed satisfactory by the operator. One-third of patients in the all-comers registry had stable angina, one-third had unstable angina, and one-third had ST-elevation MI. The preliminary analysis included 959 patients with 1,165 stented lesions in vessels with a diameter of at least 2.5 mm.

At the end of the procedure, FFR measurement using a novel monorail optical pressure sensor catheter revealed that 43% of the lesions had a suboptimal FFR value of 0.90 or less.

“Just this year, two meta-analyses showed that a cutoff of 0.90 is important to define a group of patients at high risk for major adverse cardiovascular events and revascularization,” noted Dr. Diletti of Erasmus University Medical Center in Rotterdam, the Netherlands.

Using the older, more conservative cutoff of an FFR of 0.85 or less, 20% of the lesions would potentially benefit from further action to optimize the physiologic result, most often in the form of additional expansion of the stent.

“We are used to thinking of FFR as a tool to understand whether a lesion has to be treated or not. Now we can also start thinking about FFR as a tool to guide PCI optimization,” the cardiologist said.

Optimization wasn’t actually performed in this observational registry. That will be the focus of FFR-REACT, a planned randomized trial investigating the clinical impact of intravascular ultrasound (IVUS)-directed FFR optimization of PCI.

In a per-patient analysis, 48% of FFR-SEARCH participants had a poststent FFR of 0.90 or less in one or more treated lesions. Another 22% had a postprocedure FFR of 0.85 or less in at least one treated lesion, while 8.9% had an FFR of 0.80, which is below the threshold for ischemia.

The primary endpoint in the ongoing FFR-SEARCH study is the 2-year composite rate of major adverse cardiovascular events, defined as MI, any revascularization, or all-cause mortality. Only the 30-day MACE rate was available at the time of Dr. Diletti’s presentation in Paris. The rate was 1.5% in patients with a postprocedure FFR greater than 0.90, 2.0% in those with an FFR of 0.86-0.90, 2.6% with an FFR of 0.81-0.85, and 2.8% with a poststent FFR of 0.80 or less. While those early between-group differences weren’t statistically significant, the trend is encouraging, he noted.

Postprocedure FFR measurement took an average of 5 minutes. The procedure was simple and safe, according to Dr. Diletti. There were no complications related to the use of the Navvus MicroCatheter technology. He explained that the device profile is comparable to a 0.022-inch diameter at the lesion site. Wire access to the vessel was maintained throughout. The rapid-exchange monorail microcatheter was inserted over the previously used standard 0.014-inch coronary guidewire. The optical pressure sensor was positioned roughly 20 mm distal to the distal stent edge. Manual pullback with measurements obtained at various locations in the vicinity of the stented lesion was repeated as necessary in order to identify where optimization, if appropriate, should be focused.

Operators were unable to crossover the microcatheter in 3.5% of cases, mostly because of vessel tortuosity or calcification.

Audience members commented that many of the low FFRs after stenting may reflect diffuse coronary disease, which can be corrected only by placing numerous additional stents, creating its own problems. Dr. Diletti offered reassurance on that score. He explained that in an IVUS substudy of FFR-SEARCH, an unstented physiologically important focal lesion or stent underexpansion was identified in 86% of the cases of low FFR.

“That means you can do something about it. In the other 14% of cases, in my opinion, you cannot do a lot because of very diffuse disease distally,” he said.

He reported having no financial conflicts of interest in connection with the study, supported by ACIST Medical Systems. The Navvus MicroCatheter is approved by both the Food and Drug Administration and the European regulatory agency.