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Coronary CT angiography with fractional flow reserve analysis (FFR_CT) may be an effective alternative to invasive coronary angiography for suspected coronary artery disease (CAD), according to investigators of the PLATFORM study.

Sixty percent of patients scheduled for invasive testing had their invasive imaging cancelled in part due to FFR_CT data. This FFR_CT-guided cohort was less likely to have catheterization without obstructive CAD at 90 days (12.4% versus 73.3% in the invasive angiography arm, P<0.0001).

At 1 year, there was no difference in major adverse cardiac events (1.04% versus 1.07%) or the composite of adverse events and vascular complications (3.63% versus 2.14%). Quality of life scores and cumulative radiation exposure (mean 10.7 versus 10.4 mSv, P=0.21) were also even between groups.

The FFR_CT-guided arm did stand out as having an advantage in terms of cost, however (mean $8,127 versus $12,145, P<0.0001), reported , of Duke University Medical Center in Durham, N.C., and colleagues online in the Journal of the American College of Cardiology.

A separate cohort with planned non-invasive testing had FFR_CT analyzed for some patients. Rates of catheterization without obstructive CAD at 90 days were not significantly different for this FFR_CT subgroup than for their peers who got only CT angiography (12.5% versus 6.0%, P=0.95).

In addition, 1-year rates of major adverse cardiac events (1% versus 0%) were too close to give either group an advantage in clinical outcomes. Costs too were similar between the two arms ($3,049 versus $2,579, P=0.82).

Douglas and colleagues did found, however, that cumulative radiation exposure at 1 year was higher for the FFR_CT arm (mean 9.55 mSv versus 6.42 mSv for CT angiography alone, P<0.001). Quality of life scores were largely similar between groups, although the 5-item EuroQOL scale showed greater improvement in the FFR_CT group (mean change +0.12 versus +0.07, P=0.02).

, of UCLA Medical Center, and , of Cedars Sinai Heart Institute in Los Angeles, expressed concern with recommending FFR_CT to all patients with suspected CAD.

In an accompanying editorial, they noted the lack of advantage among FFR_CT patients in the non-invasive arm: "Costs were higher in the planned noninvasive cohort, even when FFR_CT was assigned a cost weight equal to coronary CT angiography, emphasizing that FFR_CT should not be universally proposed to patients during CAD work-up but considered in patients designated to invasive coronary angiography."

The PLATFORM study included two prospective cohorts of a total 584 consecutive patients who had stable, new-onset chest pain and were deemed to have intermediate odds of obstructive CAD, divided into those with a planned noninvasive test or planned invasive angiography. Those two groups were further subdivided into sequential cohorts.

In the initial period, for the two cohorts respectively, patients got usual care testing -- invasive or not, as planned by their local clinicians -- or the planned standard invasive coronary angiography. In the second period, both cohorts got FFR_CT instead of planned testing.

The authors acknowledged their small sample size and the relatively brief follow-up duration, one too short to detect an impact on clinical outcomes.

Packard and Karlsberg added that "the following caveats should be noted: the study was conducted in European centers and reflects local practice patterns, which cannot be assumed to be identical to American centers. Moreover, as the PLATFORM trial was not a randomized trial, the decision to medically manage or directly send patients to the cardiac catheterization laboratory must be examined more closely."

"The study was underpowered to test whether this decrease in invasive coronary angiography led to significant differences in 'hard' cardiovascular events such as fatal myocardial infarction, acute coronary syndromes, or urgent revascularizations," the editorialists also noted. What's more, "FFR_CT values were available in only 58% of noninvasive and 60% of invasive arm cases, respectively, for clinical decision making."

The duo commented that their experience with FFR_CT has not been easy, rattling off obstacles, such as the lack of insurance reimbursement and concern about relying on this modality alone.

Nonetheless, they acknowledged the advantage to FFR_CT "in what remains an Achilles' heel of coronary CT angiography: decreased accuracy in the setting of significant calcification."

"For FFR_CT to gain broader use, outcomes trials similar to the FAME trials should be performed to unequivocally demonstrate the central role this technology can play in managing patients with CAD," they suggested.

"Currently, FFR_CT is only being used as a 'surrogate' to invasive FFR. We should not assume this surrogate measure has the same outcome associations as invasive FFR until these measures meet the same standards in similarly designed rigorous trials."