Valves in pulmonary veins: New approach for the heterotopic treatment of mitral regurgitation

Abstract

Introduction

Severe mitral regurgitation (MR) can be surgically addressed when the operative risk is considered acceptable. If not, several percutaneous approaches have been developed, including percutaneous mitral valve replacement and edge-to-edge repair. However, there is still an unmet need for a procedure to manage patients who are too frail for cardiac surgery and for whom current percutaneous options are contraindicated or have failed. We hypothesized that the implantation of percutaneous valves within the pulmonary veins (PV) could protect the patient from the consequences of a severe MR.

Objective

To design a synthetic valve that can be implanted in PVs for the heterotopic treatment of severe MR and test its performance in restoring cardiac output (CO) in a phantom model.

Method

An innovative process to produce customizable synthetic prosthetic valves was developed: molds of a valve prosthesis designed to be inserted in a PV were 3D-printed and used to produce prostheses made of polyvinyl alcohol hydrogel. Subsequently, in vitro tests have been conducted to evaluate the performance of the prosthetic valves under physiological conditions. The phantom includes 6 main components mimicking a left atrium (LA) with 3 PVs, a 5 mm diameter orifice as depressurization system (DS), an anatomically correct mitral valve, a dynamic left ventricle, an aortic valve, and an aorta (Figure 1). The coaptation of the mitral valve leaflets was adjusted to simulate levels of MR. Four different conditions were tested three times each: 1) No MR, no valve in PVs and DS closed (control position); 2) Severe MR, no valve in PVs and DS closed; 3) Severe MR, valves inserted in each PV and DS closed; 4) Severe MR, valves inserted in each PV and DS open to mitigate a rise in LA pressure (LAP). Forward cardiac output (CO) and mean LAP were assessed.

Results

In the control condition mimicking a healthy subject, the CO was 3.96 ± 0.05 L/min and the mean LAP was 2.8 ± 1.2 mmHg. When severe MR was induced (condition 2), the CO dropped to 2.16 ± 0.16 L/min and the mean LAP increased to 4.0 ± 1.1 mmHg. Once prosthetic valves were added in the PVs (condition 3), the CO rose up to 3.37 ± 0.33 L/min and the mean LAP up to 31.7 ± 1.3 mmHg. With the DS opening (condition 4), the mean LAP dropped to 22.9 ± 1.5 mmHg with a slight reduction in CO (2.98 ± 0.04 L/min).

Conclusion

This proof-of-concept study successfully demonstrates that implantation of valves in PVs can restore CO in presence of severe MR and that a DS can mitigate the resulting rise in LAP.