Should We Assume the Performance of a Bioprosthetic Valve to be the Same in Aortic and Pulmonary Position?

Central Picture

The durability and hemodynamic performance of the Inspiris Resilia Valve (IRV) is well-documented in the aortic position, but can we assume the same outcomes when it is implanted in the pulmonary position? Kaneko et al ¹ recently presented the results of their 8-year propensity-matched analysis of the IRV at the 2025 Heart Valve Society meeting, reporting excellent freedom from structural valve deterioration (99.3%) in Resilia tissue compared to non-Resilia tissue. The question is, should we assume the same durability and performance of a bioprosthetic valve in the aortic and pulmonary position? Are the data presented for aortic bioprosthetic valve reassuring enough while implanting the same valve in a pulmonary position?

Perri and colleagues have presented a compelling study on the performance of the IRV in pulmonary position. They retrospectively included 45 patients from 7 to 47 years old with tetralogy of Fallot. They sutured the posterior sewing ring of the IRV to the native pulmonary annulus and used a large bovine pericardial patch to reconstruct the right ventricle outflow track (RVOT) and suture the anterior sewing ring of the IRV. This is a technique commonly used for pulmonary valve surgery using a bioprosthetic valve. They reported 6 cases (13.3%) of bioprosthesis dysfunction. All patients who developed bioprosthetic dysfunction underwent implantation of an IRV size 25 mm.

In this editorial, we explore key hypotheses that still need to be elucidated that may explain why or why not the durability of IRV may differ in the aortic position and in the pulmonary position.

Does the Pulmonary Root Lack Support?

Hypothesis: The pulmonary root is more distensible than the aortic root, because it does not have a fibrous annulus. Indeed, the pulmonary root expands by 33% under normal right ventricle pressure, which could cause leaflet malcoaptation and valvular regurgitation.

Nguyen et al ² present an interesting way of solving that problem by implanting the valve in a conduit, therefore preserving the geometry of the RVOT. They reported better outcomes when the IRV was implanted in a conduit: “valve durability was significantly poorer when implanted in the native RVOT compared with as a composite valve graft” and that “freedom from at least moderate PR […] was also lower when the Inspiris valve was implanted in the native RVOT compared with as a composite valve graft.” ² This finding could support the hypothesis of early prosthesis regurgitation and failure.

Is the VFit Technology to Blame for Early Prosthesis Regurgitation?

Hypothesis: VFit technology of the IRV, present in valve sizes 19 to 25 mm, might expand, causing leaflet malcoaptation. Perri and colleagues corroborate this hypothesis by mentioning that size 27 mm IRV—which does not utilize VFit technology—did not show failure.

However, Nguyen et al ² report regurgitation in size 27 mm IRV—which does not utilize VFit technology—and further states that they “did not observe a difference in the hazard of Inspiris valve failure as a function of valve size, but this may be due to limited sample size within each valve size.” Furthermore, Ragheb et al ³ also report regurgitation in a size 27 mm IVR.

While the VFit technology might not be the main cause of early regurgitation, the flexible alloy frame could have a role to play.

Does the Pulmonary Circulation Generate Enough Pressure to Close a Thicker Valve?

Hypothesis: IRV leaflets, treated with special chemical technology that eliminates free aldehydes, are thicker than other bioprosthesis and might behave differently on the right side. Perri and colleagues’ hypotheses that the lower pulmonary circulation pressure may not be sufficient to close the prosthetic leaflets.

Nguyen et al ² also mention this hypothesis. If this hypothesis is true, it would be difficult to explain why the leaflets in a conduit are able to properly coapt in the pulmonary circulation. This implies that the pulmonary circulation might be able to generate enough pressure to properly close the valve.

Does Using a Patch Create More Turbulence?

We hypothesize that the operative technique described by Perri and colleagues, specifically the use of a pericardial patch to reconstruct the RVOT, might create more turbulence, thus faster prosthesis dysfunction.

Ragheb et al ³ collected data about patched and native RVOT implantation. Unfortunately, they presented this data pooled together. More experimental data are required to confirm or infirm this hypothesis.

Can the Smaller Sewing Cuff Cause Leaflets Restriction?

We hypothesize that the smaller sewing cuff might cause valve tilting when suturing, and the struts might touch native tissue and become engrained with time. This might trap leaflets and cause restriction, thus explaining the regurgitation.

Our hypothesis might also support the findings of Nguyen et al. ² Since implanting a valve in a conduit prevents the struts from touching the native tissue. More experimental data are required to confirm or infirm this hypothesis.

Could Previous Sternotomies Explain Early Bioprosthesis Dysfunction?

The cohort of Perri and colleagues is mainly composed of repeat procedures: “All patients, except 5, underwent at least 1 previous sternotomy.” This represents 88.9% of the cohort. However, no subanalysis was performed for previous sternotomies.

The Inspiris Resilia cohort of Ragheb et al ³ is 97% composed of patients who have had at least 1 previous surgical intervention. No univariable or multivariable Cox regression analysis for moderate pulmonary regurgitation was performed for this variable. ³

The Inspiris Resilia cohort of Nguyen et al ² is 94.2% composed of previous surgical interventions before propensity score matching, and 98.6% after propensity score matching, and no statistical analysis was performed for previous surgical interventions. ²

It is certainly difficult to have a sufficient number of patients without past procedures to compare to patients who had previous sternotomies. However, it would not be farfetched to hypothesize that previous procedures, because of thicker and more fibrotic tissue, might have a role to play in the flexibility of the prosthesis excursion, the flow dynamics, and early prosthesis degradation.

Could Different Pathologies be More Favorable to the Implantation and Durability of IRV?

The cohort of Perri and colleagues is mainly composed of patients with tetralogy of Fallot (62.2%), pulmonary stenosis (22.2%), pulmonary atresia (8.9%), Fallot canal (2.2%), and transposition of the great arteries (2.2%). All these etiologies have a physiopathology unique to them, which raises the question of whether IRV performs better under certain circumstances and worse under others.

Ragheb et al ³ reported no statistical significance between tetralogy of Fallot and valvular pulmonary stenosis or pulmonary atresia for moderate pulmonary regurgitation in a univariable Cox regression analysis (p = 0.25). They also report no statistical significance for right ventricle outlet gradient >26 mmHg (p = 0.14) or reintervention rate (p = 0.74). ³ In other words, IRV's early failure cannot be attributed to the underlying disease.

Furthermore, Nguyen et al ² in their propensity score matched cohort—using diagnosis (tetralogy of Fallot, truncus arteriosus, congenital pulmonary stenosis, pulmonary atresia, etc) as independent variables in their model—reported statistical significance in freedom from valve failure in Inspiris versus non-Inspiris valves, as well as freedom from moderate pulmonary regurgitation. ² This finding further corroborates the hypothesis that IRV has an intrinsic design factor making it more susceptible to early deterioration.

Conclusion

In conclusion, multiple retrospective studies have reported early deterioration of IRV in the pulmonary position compared to other valves and presented multiple hypotheses, without conclusively identifying the main factor. Whatever the case might be, it is certainly related to the valve design and the surgical technique. While IVR might be right for now and ready for tomorrow in the aortic position, it further needs investigation and follow-up data while implanted in the pulmonary position. This editorial does not provide a definitive answer to the early structural deterioration or valve regurgitation but presents an interesting perspective to consider and investigate further. All in all, further research is warranted to study the long-term outcomes of IVR in the pulmonary position and the mechanisms of failure.