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

Condition(s) studied

Investigational drug(s) / intervention(s)

Double-TAP post-dilatation: If patient is randomized to treatment arm the TAVI delivery balloon is aligned at valve level and reinflated to nominal volume for 3 seconds under rapid pacing.

Study summary

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.

Eligibility

Primary outcome measure(s)

• Hypoattenuated Leaflet Thickening (HALT) — 30 days
  HALT (at least one thickened TAV leaflet involving \> 25% of the leaflet curvilinear dimension as assessed at cardiac CT)
• Co-primary: VARC-3-defined safety — 30 days
  Composite of 1) freedom from all-cause mortality; 2) freedom from all new stroke; 3) freedom from VARC type 2 to 4 bleeding; 4) freedom from major vascular, access-related, or cardiac structural complications; 5) freedom from acute kidney injury stage 3 or 4; 6) freedom from moderate or severe aortic regurgitation; 7) freedom from new permanent pacemaker implantation caused by procedure related conduction abnormalities; and 8) freedom from surgery or intervention related to the device in accordance with the third Valve Academic Research Consortium (VARC-3) criteria at 30 days.

Trial sites (5)

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