Abstract Background A sizeable proportion of deferred patients based on non ischemic FFR, continue to experience symptoms. Evaluation of serial temporal changes in FFR may help guide follow up and management in such patients. Methods Consecutive patients undergoing FFR evaluation in whom PCI was deferred were followed. Patients who had repeat angiographic evaluation for recurrent symptoms and who had FFR re-measured in the same artery were analyzed. In patients who had progression to ischemic FFR, we performed multivariate analysis to identify the factors most associated with accelerated progression. Results 796 non-ischemic lesions in 559 patients, by FFR were deferred for medical management. Among them 48 patients with 56 lesions underwent repeat FFR evaluation at a mean follow up of 686 ± 418 days (range 30 to 1649) for persistent or recurrent symptoms. FFR value significantly changed from initial mean of 0.85 ± 0.04 to 0.82 ± 0.07 with a mean difference of 0.032 ± 0.01 (P = 0.003) (Figure 1a). 51 lesions were initially non ischemic with FFR > 0.80. Among these 22 (41%) lesions progressed to develop ischemia (FFR < 0.80) from an initial mean FFR of 0.85 ± 0.037 to 0.75 ± 0.051 with a mean difference of 0.1 ± 0.054 ( P <0.001) (Figure 1 b). Among the remaining 30 patients there was no significant change in FFR (0.87 ± 0.048 vs 0.87 ± 0.041; mean difference 0.006 ± 0.05; P = 0.54). Differences in baseline characteristics were as follows (lesion progression vs. none): Age (61±5 vs 63±5;p=0.12), stenosis (58±12 vs 52±10;p=0.07) FFR (0.84±0.04 vs 0.86±0.05;p=0.2); DM (29% ± 58%; p=0.07) smoking 43 ± 48%) prior MI/revascularization (90% vs. 79%; p=0.34) CKD 5% vs. 15%; p=0.24) ACS (38% vs. 38%) and LAD (38% vs. 36%). Conclusion Among lesions, initially deferred PCI based on non ischemic FFR, recurrence of symptoms should prompt re-evaluation of ischemia as a large proportion (~40%) of these lesions may demonstrate progression to ischemia (FFR<0.80).Factors associated with progressive decline in FFR warrant further study.Repeat FFR value changesRepeat FFR with ischemia development