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Functional data from computed tomography-derived fractional flow reserve (FFR_CT) assessment altered the trajectory of treatment for patients with chest pain, a study found.

After clinicians judged the best therapy for each patient based on CT angiography alone, they changed their minds 36% of the time when subsequently given FFR_CT values. The choices included were optimal medical therapy, percutaneous coronary intervention, coronary artery bypass grafting, or insufficient information.

"This difference is explained by a discordance between the CT angiography and FFR_CT -derived assessment of lesion severity," wrote , of University Hospital Southampton in the U.K., and colleagues, reporting online in .

The team found that 29.5% of vessels initially graded as having 90% or greater stenosis actually had FFR_CT values above 0.80. On the flip side, 4.6% of cases deemed to have no obstructive disease (stenosis of 50% or less) had a positive FFR_CT result.

"This study demonstrates a proof of concept: that the availability of FFR_CT results in a significant change in the labelling of significant coronary artery disease and therefore on the management of patients compared with CT angiography alone," the authors concluded. "FFR_CT has potential as a screening tool for patients with chest pain."

Writing in an , , of Stanford University Medical Center in California, and , of Kyungpook National University Hospital in South Korea, said, "Curzen and colleagues should be congratulated for providing further evidence that it is time to 'pull the ripcord' on relying on CT angiography alone for treatment decisions in our patients with stable chest pain by adding FFR_CT to our algorithm."

"These findings highlight the effect FFR_CT can have on decision processes even when used routinely in a consecutive group of patients. Because of the high negative predictive value of a normal CT angiography, one would not anticipate much added benefit from FFR_CT in cases with normal CT angiography, which appeared to be a significant minority in this study. Therefore, if one only applied FFR_CT to cases in which the CT angiography was abnormal, one could anticipate even more dramatic differences in the treatment plan before and after incorporation of the FFR_CT data."

Fearon and Lee suggested that an ideal diagnostic tool would combine the anatomic resolution of CT angiography with reliable data about the functional significance of the visualized stenoses. Still, showing that FFR_CT really improves clinical outcomes will be necessary before its routine application, the editorial added.

The study by Curzen et al was a subanalysis of 200 consecutive patients with stable chest pain who underwent CT angiography in the NXT trial. The researchers agreed on a management plan for each patient depending on the imaging, and they could change their mind after functional data were revealed.

Upon learning the FFR_CT data, the clinicians placed all the patients who were originally in the "more information required" category into revascularization (26%) and optimal medical therapy groups (74%).

In addition, 12% of the patients assigned to medical treatment were redirected towards revascularization, and another 30% originally assigned to percutaneous coronary intervention were given optimal medical therapy instead.

"It is interesting to note that these data mimic those seen in the original RIPCORD study of invasive coronary angiography and invasive FFR," the investigators commented.

That said, the editorialists presumed that Curzen's group did not include all 484 patients in the NXT trial "to mimic" that original RIPCORD investigation. Also missing from the study, they wrote, are data from invasive FFR that was performed in all patients in the NXT trial.

"It would have been interesting to see how well the management plan based on the FFR_CT data correlated with the ultimate treatment decision based on the invasive coronary angiogram and FFR assessment."