Effect of TAVI on Epicardial Functional Indices and Their Relationship to Coronary Microvascular Function

BACKGROUND: The anatomic and physiological changes associated with severe aortic stenosis may influence the functional evaluation of coronary stenoses. In this study, we aimed to assess changes in functional resting and hyperemic indices before and immediately after transcatheter aortic valve implantation (TAVI) and their relationship with microvascular resistance. METHODS: In this pooled analysis of 3 prospective observational studies, fractional flow reserve (FFR), resting full-cycle ratio (RFR), and resting distal coronary pressure to aortic pressure ratio (Pd/Pa) were measured in patients with severe aortic stenosis before and after TAVI in the left anterior descending artery. Coronary microcirculation was also assessed using thermodilution-based methods, with microvascular resistance reserve (cutoff ≤3) used to identify coronary microvascular dysfunction. RESULTS: A total of 126 patients were included. Baseline Pd/Pa, RFR, and FFR measurements were 0.93±0.04, 0.90±0.07, and 0.89±0.07, respectively. Immediately post-TAVI, a small but significant decrease was observed for both RFR and FFR (RFR, 0.88±0.08; FFR, 0.88±0.08; P<0.05 for all). Coronary flow reserve and microvascular resistance reserve also remained unchanged. Applying the established cutoff values, 16 (12.7%) vessels had a positive FFR, while a higher proportion of vessels were positive for Pd/Pa and RFR (35.7% and 43.7%, respectively; P<0.001). The concordance between pre- and post-TAVI FFR was higher (92.8%) compared with Pd/Pa (75.4%) and RFR (73.8%) (P<0.001 for both). The rate of disagreement between resting and hyperemic indices remained unchanged, regardless of the presence of coronary microvascular dysfunction. CONCLUSIONS: TAVI is associated with a small but significant reduction in FFR and RFR immediately post-procedure. Overall, the agreement between pre- and post-TAVI values of FFR was higher compared with resting indices.