Abstract 4366340: Use of 3D Virtual Modeling to Guide Mitral Valve Partial Heart Transplantation in a Pediatric Patient with a Mechanical Mitral Valve

Background: Mitral valve (MV) partial heart transplantation (PHT) is an exceptionally rare and technically demanding procedure, with only one prior case reported using a living donor valve. This case represents the first known MV PHT to replace a mechanical prosthesis. In patients with prior valve replacement, distorted cardiac geometry and absent subvalvular structures pose significant challenges to donor valve implantation. Precise placement and tensioning of donor chordae necessitate accurate spatial measurements that conventional imaging cannot reliably provide. 3D virtual modeling offers a patient-specific solution to quantify anatomic relationships and support high-precision surgical planning for these complex and unprecedented interventions. Methods: A 12-year-old male with a history of VSD closure and supra-annular 21 mm mechanical MV replacement at age 2 presented with severe prosthetic valve stenosis and was evaluated for MV PHT. ECG-gated contrast-enhanced cardiac CT scans were acquired in both systole and diastole (Fig 1A ). 3D digital hearts (DHs) were reconstructed for each phase to include the ventricular myocardium, mechanical valve, and remnant anterolateral papillary muscle (PM) ( Fig 1B ). The resulting DHs enabled direct measurement from the native annular plane to the PM, providing a critical spatial reference to guide intraoperative donor chordae placement. Results: The DHs revealed annular-to-PM distances ranging from 25 to 35 mm ( Fig 1C ). These measurements informed the placement of pledgeted sutures for donor chordae attachment on the LV free wall, ensuring physiologic leaflet tensioning. The DHs also clarified spatial constraints posed by the prior valve and altered LV geometry, assisting surgical decision-making beyond what static imaging allowed. The patient underwent successful MV PHT with serial follow-up echocardiography showing stable MV function with mild regurgitation and preserved biventricular function. Conclusion: This case highlights the critical role of 3D virtual modeling in the planning of MV PHT, enabling precise intraoperative chordal placement in the absence of native subvalvular anatomy. Patient-specific DHs allowed accurate quantification of complex spatial relationships that were otherwise inaccessible, enhancing surgical confidence and procedural precision. Integration of DHs into preoperative workflows may broaden the feasibility of complex reconstructive valve strategies in pediatric and reoperative populations.