Introduction

Various factors may lead to the degeneration of a bioprothesis, including Structural Valve Deterioration (SVD), which affects the durability of the bioprothesis and limits the quality of life and life expectancy of the patient [1]. When patients have a Mitral Valve (MV) that exhibits SVD, they usually need to undergo Mitral Valve Replacement (MVR) again, but a traditional thoracotomy is traumatic, especially for high-risk surgical patients [2]. Transcatheter Mitral Valve-In-Valve Replacement (TMViVR), as an alternative to traditional surgical procedures, may not only rapidly help patients to relieve but also significantly reduce the risk of bleeding and stroke [3]. However, patients undergoing TMViVR still face many challenges, such as postoperative left ventricular outflow tract obstruction, a Paravalvular Leak (PVL), and patient-prothesis mismatch [4]. In this case report, we describe how we printed a 3-Dimensional (3D) model of the anatomical characteristics of a high surgical risk patient before the procedures and conducted simulations to confirm the diagnosis and successfully complete the TMViVR.

Baseline Characteristics and Preoperative Imaging Evaluation

The patient underwent Mitral Valve Replacement (MVR) 11 years ago for mitral stenosis, and he underwent tricuspid valvuloplasty 6 years ago because of tricuspid regurgitation after the MVR. One year ago, the patient developed clinical symptoms again, and Transthoracic Echocardiography (TTE) showed aortic regurgitation combined with stenosis (PG_max=25 mmHg). A transcatheter aortic valve replacement was performed. Two months ago, the patient developed palpitations, shortness of breath, and chest tightness, and the symptoms continued to worsen. Physical examination showed that the Blood Pressure (BP) was 130/75 mmHg and that the was New York Heart Association (NYHA) functional class III; a systolic murmur occurred in the area of the MV osculation. In addition, the N-terminal pro-B-type natriuretic peptide level reached 574.7 pg/mL. Computed Tomography Angiography (CTA) and TTE showed an MV of SVD (anterior leaflet prolapse with incomplete closure); TTE displayed V_max=270 cm/s, PG_max=29 mmHg, PG_mean=9mmHg, Ejection Fraction (EF) = 57%, and massive regurgitation above MV (volume=29 mL) (Figure 1).

Figure 1: Assessment of computed tomography angiography before the procedure using Circle Cardiovascular Imaging CVI42 software (Calgary, AB, Canada). (A) The annular area of the prosthetic mitral valve was 462.9 mm^². (B) The left ventricle was 91.0 mm in the long axis and 61.8 mm in the short axis, and the left atrium was 64.9 mm in the long axis and 59.7 mm in the short axis. (C) The left and right axes of the left ventricle and left atrium were 60.3 mm and 65.6 mm, respectively. (D) By simulating a 26-mm valve, the relationship between the stent and the neo-left ventricular outflow tract could be observed. (E) The area of the neo-left ventricular outflow tract was 573.7 mm² after simulating the process of implanting the valve. (F) The projection angle of the released valve implanted by trans-septal access is RAO55, CAU12.

3-Dimensional Printing and Preoperative Simulation

The Digital Imaging and Communication of Medicine format of the patient’s CTA data was imported into Materialise Mimics version 21.0 (Leven, Belgium) software, and the 3D reconstructed MV model was segmented by the threshold segmentation function. Using Materialise 3-Matic (Leven, Belgium) software, the 3D reconstructed model was digitally processed, including shell extraction, cutting, smoothing, and repair, and the anatomical structures were completely restored (Figure 2A). Finally, the digital model was exported to Standard Tessellation Language format, and the files were imported into the Polyjet 850 multimaterial full-color 3D printer (Stratasys, Inc., Eden Prairie, MN, USA) for printing. The 3D printed MV model was obtained by editing and printing different tissues made from different materials (Figure 2B). When working with the 3D printed MV model, surgeons may intuitively and fully understand the specific anatomical structures of the MV and the adjacent tissues and use the model and the Prizvalve balloon-expandable valve (Newmed Medical Co., LTD., Shanghai, China) to simulate the transatrial septal approach when performing the bench test, which may show the influence of the bioprosthetic coaxiality on the different puncture locations on the atrial septum (Figure 2C-F). In addition, the process of releasing the balloon-expanded bioprothesis can be simulated to formulate the surgical strategy more accurately and effectively, so that the procedures may be carried out smoothly and successfully.

Figure 2: A 3-dimensional printed model was used to simulate the procedure during the bench test. (A) 3-Dimensional reconstructed model in the lateral view. (B-C) The 3-dimensional printed model in the lateral view and the left atrium view. (D-E) TMViVR procedures were simulated: the catheter went through the left atrium and released the balloon-expandable valve successfully. (F) Released valve from the plane of the left atrium. LA: left atrium; LV: left ventricle; MV: mitral valve.

Procedural Steps

The left femoral artery of the patient was taken as the puncture point, and 2 mL of 2% lidocaine was used for local anesthesia. After a successful puncture, a 6F arterial sheath was placed, and 3000 U of heparin was injected intravenously. Transesophageal echocardiography performed before the procedures showed severe paravalvular regurgitation in the MV (Figure 3A). Afterwards, a 6F sheath was placed through the right jugular vein to deliver the pacing lead into the right ventricle. The 6F femoral sheath was inserted into the right femoral vein, and the 9F Cook sheath was replaced. After successfully puncturing the atrial septum, a J wire was inserted into the left atrium, and the puncture site of the atrial septum was dilated with a balloon. The 8F adjustable bendable sheath was inserted into the left atrium to guide the MPA2 catheter, and the loach guide wire was guided to the left ventricle. A Lunderquist guide wire was placed into the left ventricle, and a 26F GORE sheath (W.L. Gore, Newark, DE, USA) was inserted into the femoral vein along the supporting guide wire. According to the preoperative imaging assessment and 3D printing model simulation results, a 26-mm Newmed interventional valve system (NewMed Medical Co., Ltd., Shanghai, China) was selected. Heparin 2000 U was added during the procedures, and the delivery system was sent to the MV along the Lunderquist guide wire (Figure 3B). When the stent coincided with the tangent position of the MV, the pacing was performed 180 times/min to release the stent and deploy the bioprosthesis (Figure 3C, D). After the implant was completed, a DSA scan showed the good position of the bioprosthesis (Figure 3E). Transesophageal echocardiography showed that the MV leaflet opened and closed normally, the blood flow rate was normal, and no PVLs were noted (Figure 3F). The whole procedure went smoothly, ending with 40 mL of intraoperative blood and 35 mL of contrast agent.