SYMmetric Valve fraME Expansion To Reduce hYpoattenuated Leaflet Thickening After Balloon-expandable TAVI: the SYMMETRY Trial

Rationale: Transcatheter aortic valve implantation (TAVI) has become the standard of care for aortic stenosis across all surgical risk categories, including low-risk, younger patients (≥70 years). As many of these patients are expected to outlive their prosthetic valves, the durability of the valve becomes an increasingly critical factor. Hypoattenuated leaflet thickening (HALT), a finding on post-TAVI computed tomography (CT), occurs in approximately 20% of patients and is associated with bioprosthetic valve dysfunction. Balloon-expandable valves seem more susceptible to HALT with an occurrence rate of 21%, compared to 16% for self-expanding valves. A recent study identified underexpansion of the transcatheter heart valve prosthesis as a key predictor of HALT at 30 days, which in turn was associated with a sixfold increase in cardiovascular mortality and a threefold increase in all-cause mortality at 1 year. Moreover, data suggest that, in the absence of post-dilatation, more than 95% of balloon-expandable valve implants exhibit some degree of underexpansion. In contrast, routine post-dilatation enhances valve expansion and hemodynamic performance without significantly increasing adverse events. The double-TAP technique-re-inflation of the TAVI delivery balloon after initial valve deployment-achieves a 9-10% increase in valve frame expansion, potentially reducing HALT risk and improving long-term outcomes. Objective: To determine whether routine double-TAP post-dilatation after balloon-expandable TAVI is safe and can reduce the incidence of HALT. Study design: Investigator-initiated, multicenter, open-label, randomized trial with 1:1 allocation to routine post-dilatation using double-TAP versus no post-dilatation immediately after balloon expandable valve deployment. Study population: 422 Patients undergoing balloon-expandable TAVI for native aortic valve stenosis Investigational intervention: TAVI with a balloon-expandable valve followed by double-TAP post-dilatation. Study design: Investigator-initiated, multicenter, open-label, randomized trial with 1:1 allocation to routine post-dilatation using double-TAP versus no post-dilatation immediately after balloon expandable valve deployment. Study population: 422 Patients undergoing balloon-expandable TAVI for native aortic valve stenosis Investigational intervention: TAVI with a balloon-expandable valve followed by double-TAP post-dilatation.

Inclusion Criteria: * Age ≥ 70 years * Patients with severe aortic stenosis undergoing TAVI with a balloon-expandable valve * Written informed consent Exclusion Criteria: * Significant valve frame under-expansion and/or ≥ moderate paravalvular leakage warranting post-dilatation at the discretion of the treating physician * Shallow implantation depth with increased risk of valve embolization upon post-dilatation * Sievers type 1 bicuspid aortic valve with calcified raphe * Indication for oral anticoagulant therapy * Estimated glomerular filtration rate \