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LAS VEGAS -- Fractional flow reserve (FFR) changed the treatment plan for a large number of percutaneous coronary intervention (PCI) candidates in a registry, while a second study showed an adenosine-free version was highly accurate for assessing PCI adequacy during the procedure.

In the , treatment plans changed only modestly in proportion planned for medication-only management versus PCI or coronary artery bypass grafting (CABG) comparing what was prospectively recorded by operators before FFR and after it, Erick Schampaert, MD, of Hôpital Sacre-Coeur de Montreal, Quebec, reported here at the .

However, 29.8% of lesions were going to be treated differently after FFR. And changes were substantial on an individual-patient level, too:

• A switch to PCI occurred for 19.1% of the 1,350 patients initially selected for medication-only treatment and 13.6% of the 119 who were to get CABG
• A shift to medical-only management occurred for 51.6% of the 7,171 initially PCI-planned patients and 30.3% of those who were to get CABG
• Less than 3% of patients switched to planned CABG after FFR

"In 2016-2018, FFR is still a valuable tool," Schampaert said at a press conference. "Still nowadays, you do need to rely on more than angiography to make the right decision."

Changes in plan were significantly more common for acute coronary syndrome patients than those with stable coronary artery disease in the registry, which included 2,217 consecutive patients enrolled from 70 hospitals across 15 countries from October 2016 to February 2018.

The study aimed for an all-comer population of those getting clinically-indicated coronary angiography, excluding only extremely tortuous or calcified coronary arteries and those with a patent bypass graft to the target vessel. But all were also coming into the cath lab with FFR planned for further PCI consideration, which meant there was patient selection at play, Schampaert noted at the late-breaking trial session.

FFR use varies widely from 5% to up to 30%, he said.

And perhaps only 20% of interventionalists are using FFR, commented press conference moderator M. Chadi Alraies, MD, MPH, of Wayne State University in Detroit.

"I would suggest that this may actually provide support to increase its use," Schampaert said at the session. "I don't know what the right percentage would be. Surely patients who come in with an acute coronary syndrome where you have localizing ECG changes and no other concomitant disease you do not need to do FFR. ... It is for the patients presenting with concomitant disease where there was no previous angina where I believe it's very important to make the right decisions for these patients."

Alraies agreed: "We are over-stenting people."

The under-stenting aspect is also important, added Abdul Hakeem, MD, of Rutgers Robert Wood Johnson Medical School in New Brunswick, New Jersey.

"The more provocative part of the presentation was one key reason people don't usually incorporate FFR is they feel if they use FFR they are less likely to put a stent," he commented. "And here the investigator demonstrated that, of the medical therapy group, a substantial proportion of patients actually required PCI."

Adenosine-Free Check on Stenting

Hakeem presented the second trial, showing that a non-hyperemic pressure ratio could work well as a surrogate for FFR to assess residual ischemia during stenting.

The ratio of distal to aortic pressure (Pd/Pa) -- essentially FFR without adenosine, which Hakeem noted is universally available and vendor agnostic -- had "excellent diagnostic accuracy" at a cutoff of 0.90 compared with FFR:

• 87% correct in identifying ischemic vs non-ischemic lesions in a reference cohort of 1,560 vessels assessed before PCI
• 85% accurate in a derivation cohort of 655 vessels assessed after PCI
• 91% accurate in a prospective validation cohort of 255 vessels

Diagnostic accuracy could be further boosted to 95% by a hybrid strategy of giving adenosine in the quarter of cases where Pd/Pa is borderline, Hakeem said at the late-breaking trial session.

A substantial proportion of angiographically-satisfactory PCI shows residual ischemia on FFR, and studies have shown that addressing that residual ischemia can improve overall hemodynamic outcome of PCI, he noted.

"There has been a trend toward using non-hyperemic pressure ratios," such as instantaneous wave-free ratio (iFR), he told attendees. "It has to do with more cath lab efficiency. On average you reduce the procedure time by 4 to 5 minutes, you reduce cost and reduce patient side effects. However, when it comes to post-PCI evaluation, none of these variables have been formally studied prospectively to tie to decision making."

He called for further studies to determine if Pd/Pa has the same prognostic implication and effect on clinical decision making as FFR.