In Vivo Feasibility and Growth of Atrioventricular Partial Heart Transplantation in a Porcine Model

Pediatric mitral valve replacement remains a significant challenge due to the lack of growth-capable prostheses, often necessitating multiple reoperations. Partial heart transplantation (PHT) has shown promise in the semilunar position but has not been studied in the atrioventricular (AV) position. This study evaluates the feasibility and growth potential of AV PHT in an in vivo porcine model.

Three Yorkshire piglets underwent AV PHT, with the donor mitral valve implanted into the tricuspid position due to animal intraoperative tolerance limitations. The first 2 animals were used to refine surgical technique. The third piglet was designated for 2-month survival with serial echocardiographic monitoring. Donor valves were procured on the day of surgery to minimize ischemic time. Postoperative immunosuppression included tacrolimus, mycophenolate mofetil, and methylprednisolone.

The survival animal tolerated the procedure well and remained clinically stable. Echocardiography demonstrated significant growth of the PHT mitral annulus from 2.0 cm to 4.3 cm, compared with 2.4 cm to 3.0 cm in the native annulus. The length of the PHT leaflet increased from 1.3 cm to 2.4 cm, whereas the length of the native leaflet increased from 1.1 cm to 1.9 cm. Nonprogressive moderate regurgitation was observed without stenosis. Gross examination confirmed excellent tissue integration without calcification or fibrosis.

This study demonstrates the in vivo feasibility and growth potential of AV PHT, representing a promising step toward growth-capable valve replacement for pediatric patients with irreparable mitral valve disease.