Physiologic evaluation of coronary lesions using instantaneous wave-free ratio (iFR) in patients with severe aortic stenosis undergoing transcatheter aortic valve implantation

Aims: We sought to assess eventual changes in iFR measurements in patients with aortic stenosis (AS) before and after TAVI in coronary lesions with different degrees of angiographic severity. Methods and results: The functional relevance of 145 coronary lesions was assessed by online iFR and FFR measurement in 66 patients with severe AS before and after TAVI, during the same procedure. The iFR-FFR classification agreement was calculated for pre-TAVI and post-TAVI measurements. Mean iFR values remained identical before and after TAVI, irrespective of the angiographic severity of the coronary stenosis (0.89 +/- 0.12 vs. 0.89 +/- 0.12, p=0.66). However, individual iFR values varied widely after TAVI and the 0.89 iFR threshold was crossed by 15% of the investigated coronary lesions. Higher iFR variation was related to a higher transaortic gradient drop after valve intervention. The diagnostic accuracy of iFR in predicting an FFR <= 0.8 was poor (65%) in lesions with severe obstructions, and tended to increase post TAVI. Conclusions: Although overall values did not change after TAVI, iFR presented significant and mostly erratic individual variations after valve replacement. Delta iFR was influenced by the extent of the transaortic gradient drop induced by TAVI. Therefore, caution is advisable in the interpretation of iFR in the presence of AS.