A novel iron bioresorbable scaffold: a potential strategy for pulmonary artery stenosis

Abstract

A big diameter bioresorbable scaffold is expected to be used for treatment of vessel stenosis of children with congenital heart disease to adapt the growth characteristics of vessel of children and avoid the late adverse events of permanent stent implanted in children. However, it is challenging to fabricate a big diameter bioresorbable scaffold that is appropriate for percutaneous implantation with enough mechanical performance and can be smoothly delivered in children's small vessel. In this study, a novel iron big and bioresorbable Scaffold (BBS) for pulmonary artery stenosis of children with congenital cardiovascular diseases was fabricated and evaluated. The BBS was made of nitrided iron tube and processed by laser cutting and polishing. The testing results of radial strength, recoil, shortening, maximal expansion diameter and side-branch accessability illustrated the BBS has good mechanical performance. The animal study showed that the percentage of area stenosis of BBSs was 18.1 ± 8.6%, 20.2 ± 5.9% and 20.4 ± 6.1% at 28, 90 and 180 days after implantation in 17 rabbits, and no malposition, thrombus, dissection or tissue necrosis in the rabbit model was detected by micro-CT, STEM and histological examinations. An φ8 × 23 mm BBS was implanted into a 55-month-old child with left pulmonary stenosis, and multiple spiral CT was conducted. No lumen area loss appeared at 1- and 2-year follow-ups in this first-in-man study. It suggested that the BBS might be a new strategy for the therapy of pulmonary artery stenosis in children.

Keywords: big and biodegradable scaffold; congenital heart diseases; intervention; nitrided iron; pulmonary artery stenosis.

Graphical abstract

Figure 1.

(A) The BBS mounted on the balloon. (B) After balloon inflation.

Figure 2.

(A) HAADF-STEM image of the nitrided iron tube. (B) EDS mapping of Fe. (C) EDS mapping of N. (D) Bright field TEM images of a Fe₄N grain from (A) viewed in the zone axis of [011]. (E) SAED pattern of the Fe₄N grain in (D).

Figure 3.

The relationships between the N concentration and the tensile strength of the nitrided iron tube.

Figure 4.

(A) Typical radial compression curve of the BBS. (B) The effects of the N concentration on the radial strength of the BBS.

Figure 5.

Evaluation of the side-branch accessability of a BBS with a size of φ 8.0 × 38 mm. (A) A fenestrated mock vessel, (B) the BBS was deployed with a cell at the window of the fenestrated mock vessel, (C) the cell was then dilated with a φ 8.0 mm balloon and (D) measuring of the inner diameter of a cell after dilation.

Figure 6.

Typical Micro-CT 2D images of the BBSs after (A) 28 days, (B) 90 days and (C) 180 days implantation in rabbit pulmonary arteries.

Figure 7.

(A) HAADF-STEM image of the degradation products of the BBS after 6M implantation. (B) SAED pattern of the area 1 shown in (A). (C) SAED pattern of the area 2 shown in (A). (D) High-magnification HAADF-STEM image of the area 1 shown in (A). (E) and (F) EDS mapping of the area shown in (D). (G) High-magnification HAADF-STEM image of the area 2 shown in (A). (H–K) EDS mapping of the area shown in (G).

Figure 8.

Typical histopathology images of the BBSs after (A) 28 days, (B) 90 days and (C) 180 days implantation in rabbit pulmonary arteries. (D–F) High-magnification images of (A–C).

Figure 9.

First-in-human implantation of the BBS. (A) DSA image before the procedure. (B) DSA image after the BBS implantation. (C) CT image at 1-year follow-up. (D) CT image at 2-year follow-up.

Figure 10.

The mechanical performance of CoCr, Mg, Zn, Fe alloys and PLLA.