iFR value impact on left internal mammary artery graft patency: iCABG study

Abstract

Aims: to assess prospectively whether instantaneous wave–free ratio (iFR) guided coronary artery bypass grafting (CABG) is superior to angiography guided in terms of graft failure and clinical outcomes at 12 months follow-up.Methods and results: iCABG (iFR-guided versus angiography-guided CABG) is a prospective, single blinded, randomized controlled trial. iFR was performed for every coronary artery with intermediate stenosis after multivessel disease patient was referred for CABG procedure. After randomization, surgical protocol was either angiography, either iFR values based CABG with exception to left anterior descending artery (LAD) – all grafted despite iFR value. Coronary computed tomography angiography (CCTA) was performed at 2 and 12 months follow-up. The primary endpoint of this study was to determine the rate of graft occlusion or hypoperfusion at 2 and 12-month follow-up and whether those findings would correlate with iFR values. We considered a composite secondary endpoint of major adverse cardiac and cerebrovascular event (MACCE) as a secondary outcome. From December 2018 to 2020 of June, 110 patients enrolled into a study. Randomised (59:51) into two groups: iFR vs. angiography-guided CABG respectively. A total of 200 iFR measurements were performed. 26 out of 59 (44%) patients were diagnosed with two vessels disease instead of multivessel after iFR was performed and unblinded in iFR-guided group: 9 (15,3%) patients/cardiac surgeons refused to perform CABG, 17 (28,8%) accepted CABG as treatment method despite new findings. Significant smaller number of grafts were performed in iFR-guided group 3 [2-3,25] vs. 3 [3-4] angiography-guided CABG (p=0,001). At 12-months follow-up CCTA scan was performed in 92 patients (92%). 23(16,2%) hypoperfused/occluded grafts were diagnosed in iFR-guided and (42)26% in angiography-guided CABG group (p<0,001). Receiver operating characteristic curve was used to determine an iFR threshold value for coronary artery stenosis, prognosing graft hypoperfusion or occlusion, based on 12-months CCTA graft patency. In patients with LAD iFR <0.85, the odds of a patent LIMA graft at 12 months were three folds higher (OR 3.0 95% CI (1.89–4.762). The odds of patent venous graft to RCA in 12 months is 2,6 higher when iFR>0,85 (OR 2.6 95% CI (1.307–5.171). In terms of MACCE, no difference (p=1.0) was found between 2 groups during one year follow up. Ethics approval number BE-2-89 (10.12.2018).Conclusions: in cases where iFR is being used, fewer significant stenoses are identified, drastically lowering the demand for CABG. Graft failure at the one-year follow-up can be reliably predicted by an iFR value above 0.85 in the coronary artery. No significant difference in MACCE was found between the two groups over the course of the 12-month follow-up.