Phenotype-specific mitral regurgitation trajectories following transcatheter aortic valve replacement in low-flow aortic stenosis.

OBJECTIVES: Mitral regurgitation (MR) evolution after transcatheter aortic valve replacement (TAVR) in low-flow aortic stenosis (LFAS) is poorly characterized. The authors evaluated MR trajectories across LFAS phenotypes, predictors of MR worsening, and associations with clinical outcomes. METHODS: The authors retrospectively studied 614 patients with LFAS undergoing TAVR: 153 with low-flow high-gradient (LFHG) (24.9%), 155 with classical low-flow low-gradient (cLFLG) (25.2%), and 306 with paradoxical low-flow low-gradient (pLFLG) (49.8%). MR severity was abstracted from clinical echocardiography reports using a 6-level ordinal scale. MR worsening was defined as a grade increase of at least 1 from baseline MR at approximately 30 days or 1 year. Multivariable logistic models identified predictors of MR worsening. Kaplan-Meier and Cox models evaluated associations of MR trajectory and LFAS subtype with all-cause death, heart failure hospitalization, and their composite. RESULTS: Among 614 LFAS patients, 443 had 30-day and 290 had 1-year echocardiographic follow-up. At 30 days, MR trajectory differed significantly across LFAS phenotypes, with the highest rate of worsening in cLFLG and the lowest in LFHG. At 1 year, unadjusted MR trajectory distributions did not differ significantly across phenotypes. In adjusted logistic models, cLFLG remained independently associated with MR worsening at both timepoints. MR worsening was associated with worse unadjusted outcomes at 30 days but was not independently associated with the composite endpoint after multivariable adjustment. LFAS phenotype, particularly cLFLG, remained the dominant predictor of adverse clinical outcomes. CONCLUSIONS: MR evolution after TAVR is phenotype-specific; patients with cLFLG have the highest risk of MR worsening and lowest event-free survival, supporting phenotype-informed post-TAVR surveillance.