New Aspects of the Dilation Process during a Valve in Valve Procedure

Background: The introduction of TAVI for the replacement of failing heart valves is one of the great stories of the last decades. Millions of patients have already been treated with transcatheter valves. Unfortunately, these prostheses do not have an unlimited durability and have to be replaced after an average of approximately 10 years. Reliable long-term data, however, are still not available. Open surgical replacement with biological valve prostheses also leads to valve malfunction after 10 to 15 years necessitating new valve replacement. To avoid re-do surgery TAVI valve in valve has become an often used option for replacement. The inner diameter of the degenerated valve, however, defines the limit for the size of the newly implanted valve. Therefore, strategies are being sought to increase the inner diameter before implantation to avoid a prosthesis mismatch. In this study, we examined the expansion process of various prostheses using different balloons and a spreader device.

Methods: We used a specifically manufactured testing device (TD) including a high precision inverse drill chuck and a digital dynamometric key to measure the forces necessary to expand various established biological heart valves by deforming/braking of the stable structures. Increase in inner and outer diameter was measured using a caliper. Furthermore we tested which of the valves could be widened by a pressure balloon (PB) pressurized up to 20 bar. High-speed videos of the expansion process were recorded using a high-speed camera.

Results: Excellent results were achieved with the Edwards Inspiris Resilia that could be expanded significantly without critical structural damage to the stent structure. Interestingly some valve prostheses could be expanded at significantly lower pressures in the drill chuck compared with the balloons (Labcor 21 mm: TD 2.65 bar versus PB 8 bar, Medtronic Hancock TD 3.6 bar, PB 18 bar). Others (Sorin Crown 27 mm) expressed quite comparable forces between both approaches (PB: 10 bar, TD: 9.43 bar). High-speed videos revealed the release of small fragments at the moment of breaking in some valves.

Conclusion: Our results show that expansion is possible by breaking or deforming the stable structures of a prosthetic valve, but the effectiveness depends strongly on the particular valve and its design. For the different valve types, suitable balloons or even expansion devices are needed, which still need to be developed. We are not surprised that fragmentation occurs in such a procedure. It is therefore imperative that such techniques are combined with downstream embolic protection devices.

Publication History

Article published online:
11 February 2025