Are elevated post-transcatheter aortic valve replacement gradients in obese patients pathological or flow-mediated?
To the editor: I read with great interest the recent article, investigating the impact of body mass index (BMI) and valve size on post-procedural gradients following transcatheter aortic valve replacement (TAVR) (1). The study provides valuable insights into the interaction between BMI and valve size, demonstrating that high BMI and smaller valve sizes are associated with higher transvalvular gradients, reinforcing the importance of individualized procedural planning. Several aspects merit further discussion.
The interpretation of elevated gradients in high-BMI patients requires caution (1). Transvalvular gradients are inherently flow-dependent, and increased cardiac output in obese patients may physiologically elevate gradients without necessarily indicating true patient-prosthesis mismatch (PPM) (2). Indexing valve hemodynamics to body surface area (e.g., effective orifice area index) or incorporating stroke volume index may provide a more accurate assessment of valve performance.
Although the authors performed multivariable analyses, adjustment for key hemodynamic determinants appears limited (1). Important factors such as stroke volume, flow status (e.g., low-flow vs. normal-flow), and annular dimensions were not included (3). Notably, the absence of data on valve oversizing may significantly influence post-procedural gradients and confound the observed associations. Given that prosthesis sizing strategies directly impact effective orifice area, incorporating these parameters would strengthen causal inference.
The categorization of BMI using a binary cutoff (≥30 vs. <30 kg/m2) may oversimplify a continuous physiological relationship (1). The discrepancy between the continuous and categorical BMI analyses in this study suggests potential loss of information. Alternative approaches, such as spline modeling or stratification into more granular BMI categories, may better characterize the dose-response relationship between BMI and gradients.
The clinical implications of the observed gradient differences remain uncertain (1). While prior studies have suggested associations between elevated gradients and adverse outcomes (4), this study was limited to 30-day echocardiographic findings without linking them to long-term clinical endpoints such as mortality, heart failure hospitalization, or valve durability.
The study cohort was limited to balloon-expandable valves from a single center (1), which may limit generalizability. Differences in valve design, particularly between balloon-expandable and self-expanding platforms, are known to influence post-procedural gradients.
Acknowledgments
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References
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- Kherallah RY, Suffredini JM, Rahman F, et al. Impact of Elevated Gradients After Transcatheter Aortic Valve Implantation for Degenerated Surgical Aortic Valve Bioprostheses. Circ Cardiovasc Interv 2024;17:e013558. [Crossref] [PubMed]
