ACURATE Neo2 Underexpansion: Prevalence and Clinical Implications

While transcatheter aortic valve replacement (TAVR) provides durable clinical benefits across a wide range of patients, technical challenges remain that may affect long-term outcomes. One such challenge is stent underexpansion, particularly at the midframe level, which has not been well characterized to date.

Kim et al. conducted a retrospective study involving 604 consecutive patients treated with the self-expanding ACURATE neo2 valve at two high-volume European centers. The objective was to determine the incidence, predictors, and clinical significance of midframe underexpansion.

Underexpansion was defined as non-parallel alignment of the commissural posts, assessed using post-implantation fluoroscopic imaging. A threshold value of Δ-Post ≥1 mm was used, based on bench and hydrodynamic testing.

The primary endpoint was a composite of all-cause mortality, stroke, or valve-related rehospitalization within one year.

Following TAVR, the mean Δ-Post was 0.5 mm, significantly higher in patients with midframe underexpansion (1.5 mm vs. 0.5 mm; P < 0.001). Underexpansion was observed in 13.9% of patients and was independently associated with a higher risk of the primary endpoint (39.3%; 95% CI: 28.8%–50.5% vs. 10.4%; 95% CI: 7.9%–13.3%; P < 0.001), including overall mortality (adjusted HR 4.07). Other independent predictors included low baseline transaortic gradients, changes in renal function, and commissural misalignment.

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Importantly, the absence of postdilation was the only independent predictor of underexpansion (adjusted OR 5.76). Postdilation significantly reduced both the prevalence and severity of frame deformation. Although valve calcification severity initially appeared to be linked to underexpansion, this association lost statistical significance after accounting for postdilation.

Conclusions

This study demonstrates that midframe underexpansion is relatively common and is associated with worse clinical outcomes at one year. Postdilation appears effective in reducing both the incidence and extent of underexpansion. However, further prospective studies are needed to confirm these findings, as the current analysis is limited by its retrospective design.

Original Title: Clinical Impact of Midframe Underexpansion Following TAVR Using a Self-Expanding Transcatheter Heart Valve.

Reference: Kim, W, de Backer, O, Renker, M. et al. Clinical Impact of Midframe Underexpansion Following TAVR Using a Self-Expanding Transcatheter Heart Valve. J Am Coll Cardiol Intv. 2025 Apr, 18 (8) 1028–1041. https://doi.org/10.1016/j.jcin.2025.02.013.