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ROME -- Fractional flow reserve (FFR) values were superior among non-ST-segment elevation myocardial infarction (NSTEMI) patients undergoing percutaneous coronary intervention (PCI) guided by optical coherence tomography (OCT) instead of angiography, a French study found, but this did not translate into better clinical outcomes.

FFR measurements were higher after cases involving OCT (0.94 versus 0.92 for angiography-guided cohort, P=0.005), observed , of France's University Hospital Jean Minjoz, who presented the at the annual meeting of the European Society of Cardiology.

Yet there was no difference in type 4a myocardial infarctions (40% with OCT versus 33% with angiography, P=0.28) and groups shared identical rates of procedural complications (5.8%) and acute kidney injury (1.6%), according to the results of the trial, which was simultaneously published online in Circulation.

In addition, there was a longer procedure time (56 versus 36 minutes, P<0.001) and use of more contrast medium with OCT (190 versus 120 ml, P<0.001) with OCT.

Performed after PCI, however, the invasive test revealed substantial rates of stent underexpansion (42%), stent malapposition (32%), incomplete lesion coverage (20%), and edge dissection (37.5%). This led operators to perform more post-stent dilation in this group (43% versus 12.5% for angiography group, P<0.0001), which also had less residual stenosis (7.0% versus 8.7%, P=0.01).

The totality of the DOCTORS trial mark "an important milestone in the journey to accumulating sufficient global evidence to support the role of OCT-guidance eventually during complex PCI and to extend the Practice Guidelines recommendations supporting its use," according to , of Belgium's Cardiovascular Research Center Aalst, and , of Klinikum Coburg in Germany.

"Whether post-PCI FFR could be used as a surrogate end point for later clinical outcomes requires prospective long-term testing in large populations with event rates high enough to allow meaningful predictive discrimination," the pair wrote in an .

Meneveau's study included 240 patients with NSTEMI -- and only a single lesion on the culprit artery without diffuse disease -- who were randomized to PCI with either OCT or angiographic guidance. There were 9 PCI centers involved, all located in France.

"Keep in mind this was a low risk population and therefore the direct clinical impact of OCT needs to be determined," said session discussant Stephan Windecker, of Bern University Hospital in Switzerland.

Also complicating the issue is that the 0.90 FFR threshold has not been validated for patients in the acute phase of NSTEMI or periprocedural myocardial infarction, he commented.

Windecker noted that 17% of the OCT group still had insufficient FFRs (below 0.90) after PCI, leading him to ask: "Can this OCT strategy be further refined?"

Wijns and Pyxaras also expressed concern over the trial's flexible OCT protocols -- particularly in the hands of non-experts.

"The current protocol was not very prescriptive, with several items for decision left to the operator's opinion," they noted. "How likely is it that the same decisions will be made [in other centers]?"