Letter: Beyond frame expansion: interpreting the implications of routine post-dilatation

We read with great interest the study by Husain et al1 and applaud the authors for this elegant and methodologically rigorous investigation. The authors combined benchtop and in vivo evaluations of routine “double-tap” post-dilatation at nominal volume following transcatheter aortic valve implantation with a balloon-expandable valve (BEV). Using a fluoroscopic calibration of valve commissural post height, they demonstrated that nominal-pressure reinflation increased frame expansion by approximately 9% across all SAPIEN 3 Ultra (Edwards Lifesciences) valve sizes, without excess procedural or 30-day adverse events1.

In a study from our group (Leone et al2), we evaluated a similar concept solely focusing on the 23 mm SAPIEN 3 Ultra, a size particularly susceptible to clinically relevant underexpansion and prosthesis-patient mismatch (PPM). Quantitative frame assessment was performed using pigtail-based fluoroscopic calibration, referencing the 10 mm spacing between radiopaque markers. This method provides a wider calibration baseline and minimises proportional measurement error compared with catheter width-based methods3. Nonetheless, this technique is inherently subject to interobserver variability, and unlike the commissural post height method, no correlation with computed tomography is available4. Distinct from the DOUBLE-TAP protocol, our trial protocol allowed additional volume of the delivery balloon during the “double-tap” (+1-2 mL in 37% of patients) and selective use of non-compliant balloons. Compared with a control group without routine post-dilatation, this strategy yielded greater valve expansion, lower transvalvular gradients, and a reduced incidence of PPM. The haemodynamic benefit was primarily observed in patients with normal flow, while those with low-flow physiology derived little measurable improvement.

Both studies, albeit with different methodologies, converge on the principle that optimisation of frame geometry may favourably influence forward-flow haemodynamics. This effect is likely most pronounced in smaller valves and in patients with a larger body surface area, where even modest gains in frame expansion can improve transvalvular gradients and attenuate PPM (non-structural valve dysfunction)5. By contrast, in larger valve sizes, post-dilatation may have little measurable impact on immediate haemodynamics yet could still mitigate leaflet malcoaptation and pinwheeling related to underexpansion − phenomena that can exacerbate leaflet stress, induce asymmetric coaptation, and predispose patients to hypoattenuated leaflet thickening over time; these mechanisms are plausibly linked to structural valve degeneration and impaired durability67. Taken together, these considerations reinforce the idea that not all valves or patient anatomies require routine post-dilatation for immediate haemodynamic optimisation, while the potential long-term benefit on leaflet durability remains an open and important question for future study.

Nevertheless, direct evidence linking optimised expansion to improved durability remains inferential. The recent PARTNER 3 data demonstrated that, despite post-dilatation in only ~21% of cases, the mean gradient at 7 years remained stable at 12 mmHg, and the cumulative reintervention rate was 6% between years 1 and 78. Although these data imply that routine post-dilatation may not be essential for maintaining favourable long-term valve function and durability, both our data and the DOUBLE-TAP findings confirm that there is little to no price to pay in terms of adverse events, thus, a tailored yet liberal approach could be reasonable to adopt.

While we commend the authors for highlighting the prevalence of BEV underexpansion, the clinical significance of nominal-volume “double-tapping” remains to be proven beyond geometric correction. Extended durability will be essential to determine whether routine post-dilatation should evolve from an optimisation tool into a standardised procedural step.

Conflict of interest statement

A. Latib has served on the advisory board for Medtronic, Abbott, Boston Scientific, Edwards Lifesciences, Shifamed, NeoChord, V-dyne, and Philips. The other authors have no conflicts of interest to declare relevant to the contents of this paper.