Coronary microvascular dysfunction in patients undergoing transcatheter aortic valve implantation: A systematic review and meta-analysis

Background: Coronary microvascular dysfunction (CMD) is a complication of severe aortic stenosis. Its prevalence after transcatheter aortic valve implantation (TAVI) and prognostic significance are understudied, as are the post-TAVI trajectories of microvascular indices. Aims: The aims of this study were to determine the pooled prevalence of CMD, the influence of the diagnostic modality, the post-TAVI coronary flow reserve (CFR) and microvascular resistance changes, and the prognostic impact of baseline CMD on major adverse cardiovascular events (MACE) in patients with severe aortic stenosis undergoing TAVI. Methods: Five databases were searched from January 2010 to December 2025 for studies involving adults with severe aortic stenosis undergoing TAVI in which CMD was assessed by wire-based thermodilution, angiography-derived indices, Doppler measurements, or stress cardiac magnetic resonance. The risk of bias and certainty of evidence were assessed using the Newcastle–Ottawa Scale and GRADE, respectively. Random-effects meta-analyses (DerSimonian–Laird) pooled CMD prevalence (stratified by modality), CFR change (mean difference; before–after design), and prognostic hazard ratios (HRs). Change in microvascular resistance was synthesized narratively. The protocol was prospectively registered (PROSPERO: CRD42025143775) and reported per the PRISMA 2020 guidance. Results: Eleven primary studies were analyzed, 10 of which (n = 1,212) contributed to the prevalence analyses. An additional study (n = 126) was included in the sensitivity analyses only. CMD prevalence was 46.8% (95% confidence interval [CI] [34.0, 59.9]; I2 = 72%) and 38.4% (95% CI [35.3, 41.7]; I2 = 0%) when assessed using wire-based thermodilution (k = 6, n = 324) and angiographic (k = 4, n = 888) indices, respectively. CFR increased post-TAVI by a pooled mean difference of +0.49 (95% CI [+0.27, + 0.71]; I2 = 72%; k = 5, n = 103 paired observations). Reductions in microvascular resistance were confined to pressure-to-velocity and reserve ratio indices, and absolute minimal microvascular resistance was unchanged (k = 4, n = 85). The HR for MACE was 3.22 (95% CI [0.98, 10.60]; I2 = 78%; k = 2, n = 585). Substantial heterogeneity reflected non-equivalent CMD definitions. Conclusion: The prevalence of CMD pre-TAVI is influenced by the diagnostic method. CFR tends to improve after TAVI, likely due to reduced resting demand rather than structural repair. The CMD–MACE association should be viewed as hypothesis-generating due to limited studies, varied CMD definitions, and incompatible HR calculations. Prospective multicenter studies with standardized CMD definitions are required.