FFR fails to improve CABG outcomes in randomized trial

Fractional flow reserve (FFR) assessment before coronary artery bypass grafting (CABG) didn’t improve outcomes compared to angiography-guided surgery, Danish researchers reported Nov. 26 in the Journal of the American College of Cardiology.

The first randomized trial to assess functional lesion testing before CABG found patients who underwent FFR before CABG experienced similar rates of graft failure at six months (16 percent) as those who received angiography-guided operations (12 percent). Also, out of the 24 lesions that were deferred because their FFR was greater than 0.80, the mean FFR dropped from 0.89 at baseline to 0.81 at six months—a slide toward functionally significant stenosis.

“FFR appears as a good refinement tool to improve PCI decisions; but considering this first set of randomized data in CABG patients, FFR may be of a lesser interest in patients oriented towards CABG surgery,” French cardiologists Gilles Motalescot, MD, PhD, and Benoit Lattuca, MD, wrote in an accompanying editorial.

The study included 100 patients who were referred for CABG at one of three Denmark hospitals. They were randomly assigned either to CABG guided by FFR or by angiography. FFR values of 0.80 prompted deferral of revascularization for those lesions, while operators for the angiography-guided group were blinded to the FFR values in those patients and went ahead with the graft plan constructed from the angiography alone.  

The mean FFR before grafting was similar in the two groups, but the number of planned anastomoses was lower, as expected, in the FFR-guided group—an average of 2.5 per patient versus 3.2 per patient in the angiography group.

However, the rate of graft failure, defined as TIMI flow grade 3 or anastomosis stenosis greater than 50 percent, was similar in the two groups at six months. Clinical outcomes like death, MI and stroke were also similar, but the deferred lesions showed a significant reduction in mean FFR upon follow-up evaluation.

“Accelerating atherosclerosis of the deferred coronary lesion is a likely explanation, and might suggest that functionally guided surgical revascularization could be associated with more repeat revascularization at longer term follow-up,” wrote lead author Anne Langhoff Thuesen, MD, with Odense University Hospital, and colleagues. “This finding was in contrast to the DEFER study and to the FAME study, in which deferral of functionally insignificant lesions in PCI-treated patients was safe.”

However, both of those studies looked at clinical endpoints and FFR wasn’t evaluated again after the index procedure, the authors noted.

The primary limitation of the study was its small sample size, which was affected by a slower-than-expected enrollment.

“Ideally, this type of study should either compare clinical outcomes in CABG populations randomized to angiography-guided or FFR-guided surgery, which would require a large sample size, or compare graft failure in FFR-negative lesions in the angiography-guided group versus (target vessel revascularization) and/or (target vessel MI) for FFR-negative lesions in the FFR-guided group,” the researchers wrote.

While their study wasn’t statistically powered to address those two questions, the authors pointed out their study was the first randomized trial to “show disease progression in deferred lesions.”

“With this limitation, our study might be seen as a feasibility study and as hypothesis-generating for a larger study,” they wrote.

Motalescot and Lattuca pointed out another reason why FFR could be more useful for PCI than CABG: The consequence of excessive treatment for PCI (stent thrombosis) is more serious than an additional vessel grafted, which might remain asymptomatic.

“For now, and while awaiting further information, the ultimate goal of CABG surgery remains to anatomically complete revascularization using arterial conduits preferentially if not exclusively,” the editorialists wrote. “This once-for-all surgical treatment may lead to a few more anastomoses than functionally needed but at no clinical cost for the patient.”