Preclinical Evaluation of a Growth‐Accommodating Transcatheter Pulmonary Valve System for Young Children

Figures

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  Figure 1. IRIS Valve development. A, The completed valve with sewn in ePTFE skirt, leaflets, and stent in a 20 mm size. The stent is laser cut from stainless steel 304 from a 3.4 mm tube and expanded. The ePTFE skirt is laser cut and sewn on inside the wall of the stent to prevent paravalvular leak. B, Demonstration of leaflet coaptation at 20 mm. The valve's leaflets elicit adequate surface area contact for the valve ensuring coaptation is met throughout the 12 to 20 size range of the valve. C, 2D CAD drawing of the IRIS Valve leaflet. Dimensions in millimeters are shown. D, Three newly cut leaflets from the laser cutter are shown. The leaflets are sutured along their curved edges. E, Cross‐sectional diagram depicting change of arc length of the leaflet from 12 to 20 mm as radius expands. At 12 mm, the leaflets have more surface area maintaining coaptation. Radial expansion of the valve causes slack and surface area to decrease while maintaining coaptation of the leaflets. 2D CAD indicates 2‐dimensional computer‐aided design; and ePTFE, expanded polytetrafluoroethylene.

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  Figure 2. Growth accommodation of the IRIS Valve through balloon expansion. From left to right the figure shows the schematics of the IRIS Valve initially deployed at its original size of 12 mm and undergoing balloon expansion to achieve full expansion at 20 mm.

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  Figure 3. IRIS Valve implantation under fluoroscopy. A, The pulmonary valve position location after contrast injection. B, Dilation of the IRIS Valve using the BIB balloon; the waist indicates native valve annulus position, C, Lateral, and D, frontal views gradient of the IRIS Valve. BIB indicates balloon‐in‐balloon.

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  Figure 4. Finite element modeling of IRIS Valve stent. A, Full view of the crimped stent where the location of maximum and minimum von Mises stresses are shown with a red and blue indicators, respectively. The height of the crimped stent is 25.7 mm. B, Coronal cross‐sectional view of stent. C, The location of the maximum stress is shown at the place where the neighboring struts make contact with each other. D, The map of von Mises stress near the middle of the stent. E, Expansion of the stent to 12 mm led to a reduction in height to 24.6 mm. During expansion, the high‐stress regions that were once present between the crimped struts are no longer exist. F, As the stent expands to 20 mm in diameter, its height reduces to 21.3 mm.

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  Figure 5. Fluoroscopic and echocardiography data of animal implantation data. A, Contrast disperses through the implanted valve to verify function and operation. The valve does not leak or regurgitate. B, Echocardiography through color Doppler confirms the absence of regurgitation and leaks for the initial implant of the valve. C, The measured size of the valve after dilation. The valve was expanded to 20 mm in size after at least 6 weeks. D, The valve shows no signs of leakage or regurgitation on echocardiography.

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  Figure 6. Echocardiographic images of the pulmonary annulus and RVOT, where the IRIS Valve is implanted, demonstrates the valve's function. A, At peak systole, Echo‐PIV shows blood flows smoothly through the IRIS Valve into the RVOT, without the formation of large vortices. B, At peak diastole no (or trace) blood flow is observed indicating the valve competence. C, Color Doppler during systole shows the maximum velocity is 71.6 cm/s. D, Color Doppler during diastole indicates no (or trace) regurgitant flow. Echo‐PIV indicates echocardiographic particle image velocimetry; and RVOT, right ventricular outflow tract.

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  Figure 7. Radiographic and pathologic images of 2 IRIS Valve samples within pulmonary artery/RVOT. A, Radiographic image of 40 kg male pig post dilation of valve. Stent fracture is absent from the frame. B, Top view of the inflow tract of 40 kg male pig. C, Top view of the outflow tract of 40 kg male pig. D, Radiographic image of 53.5 kg male pig post dilation of valve with no stent fracture. E, Top view of the inflow tract of 53.5 kg male pig. F, Top view of the outflow tract of 53.5 kg male pig. RVOT indicates right ventricular outflow tract.

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  Figure 8. H&E staining of the IRIS Valve in the RVOT. A, Full field of view shows the stent is fully integrated into the RVOT; B, C, and D, show 4×, 10×, and 20× views of the stent (white label) and suture (yellow dots). The ePTFE skirt is shown by a black arrow. The IRIS Valve's porcine leaflets are in magenta color as indicated with black arrows is (A) with surrounding overgrown tissue (pink). ePTFE indicates expanded polytetrafluoroethylene; and RVOT, right ventricular outflow tract.