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Stenting guided by quantitative flow ratio (QFR), derived from angiography without a pressure wire or use of drugs to induce hyperemia, improved major adverse cardiovascular outcomes compared with visually assessed angiography alone, the randomized FAVOR III China trial showed.

The added information on physiologic significance of coronary stenosis from this novel technology yielded a 35% relative reduction in the 1-year composite of death, myocardial infarction (MI), or ischemia-driven revascularization (5.8% vs 8.8% with angiography alone, P=0.0004).

Peri-procedural MI drove the difference, but the other components together still showed a significant relative 36% advantage to QFR guidance (3.1% vs 4.8%, P=0.0073), reported Bo Xu, MBBS, of Fuwai Hospital in Beijing, at the Transcatheter Cardiovascular Therapeutics (TCT) meeting.

Along with the presentation at the late-breaking clinical trial session of the hybrid virtual and live event from Orlando, the study appeared in .

"The simplicity and safety of QFR compared with wire-based physiological measurements should facilitate the adoption of physiologic lesion assessment into routine clinical practice," Xu concluded.

TCT press conference panelist Giuseppe Tarantini, MD, PhD, of the University of Padova in Italy, agreed, predicting a recommendation in the next set of guidelines.

"This is, I think, a milestone in our community not only because it is easier to use compared to other lesion-specific indexes like FFR [fractional flow reserve] or iFR [instantaneous free-wave ratio]," he said, but also because it could expand the lagging use of physiology in interventional cardiology.

Despite a strong recommendation in European guidelines for pressure wire-based physiology to assess hemodynamic relevance of intermediate-grade stenoses, "this method is largely underused in practice because of long procedural time, potential complications from pressure wire instrumentation, side effects from hyperemic agents, and costs," Xu's group noted.

Median online QFR measurement time came out at 3.6 minutes, and more than 97% of the coronary angiogram could be used, which "means QFR is very, very feasible in our routine practice," Xu said at a press conference.

QFR involves 3D artery reconstruction and measurement of blood flow velocity derived from two image runs of the standard angiogram with an angle difference of at least 25° in order to measure pressure drop across a stenotic lesion.

The included 3,830 adults in China undergoing coronary angiography for stable or unstable angina or acute MI within the prior 72 hours. They were randomized to an angiography-guided strategy based on visual assessment of lesions by local standards of practice or to QFR guidance from measurement of all coronary lesions where the visual stenosis was between 50% and 90%, with a cutoff of 0.80 to determine whether to proceed with PCI or deferral.

Notably, patients were blinded to their study group assignment with a 10-minute delay for QFR or sham calculation before the PCI procedure, listening to music on headphones during the procedure, and no QFR results allowed in their medical notes.

Operators were also required to identify before the procedure the target vessels they intended to treat with standard angiography guidance, which showed how much QFR guidance changed their strategy.

The QFR group had significantly fewer intended vessels actually treated (84% vs 96%). Fully 23% of patients had a change in strategy in the QFR group, compared with 6% in the angiography-alone group. Those were mostly deferral of treatment of at least one vessel (20% vs 5% in the standard care group), with just 4% getting additional vessels treated outside the original plan.

Overall, nearly 10% fewer patients got PCI at all with QFR guidance (90.5% vs 99.1%).

"QFR has a very high negative predictive value," commented Javier Escaned, MD, PhD, of the Hospital Clinico San Carlos in Madrid, from the meeting's virtual audience. "I guess most lesions with deferred revascularization in the QFR arm were truly non-flow limiting stenoses."

Several different technologies have been developed with QFR, noted TCT press conference moderator Roxana Mehran, MD, of the Icahn School of Medicine at Mount Sinai in New York City.

"It could give you quick edge protection just placing your cursor over the area of interest and getting the QFR for that vessel. It would be, I think, an easy training and someone could do that in the control room," she said. "Obviously, the insurance companies would love it. It's one less wire, one less payment."

However, "it's not there yet," argued Shmuel Banai, MD, of Tel Aviv Medical Center in Israel, as a panelist at the TCT press conference. "It takes some time, 10 to 15 minutes, up in the control room to correct the software, to show the correct edges, so it takes time and the operator inside the room doesn't have patience to wait every time for the results."

A trial comparing QFR head to head against FFR, the , is now underway.

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