Implantation of personalized, biocompatible mitral annuloplasty rings: feasibility study in an animal model

Abstract

Objectives: Implantation of an annuloplasty ring is an essential component of a durable mitral valve repair. Currently available off-the-shelf rings still do not cover all the variations in mitral annulus anatomy and pathology from subject to subject. Computed tomography (CT) and echo imaging allow for 3-D segmentation of the mitral valve and mitral annulus. The concept of tailored annuloplasty rings has been proposed although, to date, no surgically applicable implementation of patient-specific annuloplasty rings has been seen. The objective of this trial was to prove the concept of surgical implantation of a model-guided, personalized mitral annuloplasty ring, manufactured based on individual CT-scan models.

Methods: ECG-gated CT angiography was performed in six healthy pigs under general anaesthesia. Based on the individual shape of the mitral annulus in systole, a customized solid ring with integrated suturing holes was designed and manufactured from a biocompatible titanium alloy by a rapid process using laser melting. The ring was implanted three days later and valve function was assessed by intraoperative echocardiography. The macroscopic annulus-annuloplasty match was assessed after heart explantation.

Results: CT angiography provided good enough image quality in all animals to allow for segmentation of the mitral annulus. The individually tailored mitral rings were manufactured and successfully implanted in all pigs. In 50%, a perfect matching of the implanted ring and the mitral annulus was achieved. In one animal, a slight deviation of the ring shape from the circumference was seen postoperatively. The rings implanted in the first two animals were significantly oversized but the deviation did not affect valve competence.

Conclusions: CT image quality and accuracy of the dimensions of the mitral annulus were sufficient for digital modelling and rapid manufacturing of mitral rings. Implantation of individually tailored annuloplasty rings is feasible.

Figure 1:

Process of ring manufacturing. (A) Cardiac CT images (0.3 × 0.3 × 0.3 mm³ resolution, end systolic); (B) manual placement of 24 landmarks on the mitral annulus; (C) 3-D shape of the mitral annulus before and (D) after smoothing; (E) computed model of annuloplasty ring following the modelled annulus; (F) ring model shown in CT images; (G) assignment of suturing holes; (H) final ring model.

Figure 2:

Ring implantation. (A) Atrial view on mitral valve; (B) preparation of sutures; (C) implanted ring; (D) explanted annulus with ring.

Figure 3:

(A) Custom-made ring for Pig 5; (B) comparison between four rings manufactured for Pigs 3–6.