P2.C042: Partial Heart Transplant: The Founding Institutional Experience

Background: Patients with irreparable congenital valvular disease require valve replacement. However, while infants receiving state-of-the-art valves continue to grow, their valve implants do not, committing patients to repeat operations until they reach adulthood. Partial heart transplantation (PHT) is a transformative approach that has the potential to revolutionize the treatment of valve replacement in children. Partial heart transplantation includes living root transplant; transplantation of a freshly procured semilunar valve either in the pulmonary position, aortic position, or both. This innovative approach is potentially curative as the transplanted semilunar valve is composed of living tissue and therefore maintains its growth potential. Here, we describe our early experience with this novel technique including the growth of transplanted valves in infants who underwent PHT.

Methods: Children requiring systemic root replacement or right ventricle-pulmonary artery conduit placement were identified and approached for enrollment. Patients underwent living homograft replacement of the pulmonic valve, aortic valve, or both, depending on their specific condition. Patients were closely monitored, immunosuppressive regiments were noted, and valve growth was tracked.

Results: Nine patients underwent PHT at our institution, with five having approximately 6 months of follow-up (Figure 1). Two patients received replacement of both the right ventricular outflow tract (RVOT) and left ventricular outflow tract (LVOT) with pulmonary and aortic valve homografts, respectively. Four patients underwent RVOT replacement with a pulmonary valve homograft, one with an aortic valve homograft for LVOT, and one with an aortic valve homograft for RVOT. Immunosuppressive regiment for our initial PHT consisted of approximately a week of steroids accompanied by mycophenolate mofetil (MMF) and tacrolimus, later transitioning to solely half-dose tacrolimus after a year. Our second PHT required discontinuation of immune suppression due to concern for significant infection at one month. Remaining immunosuppressive regiments transitioned to half-dose of tacrolimus after a month. All valves demonstrated growth over the interval timeframe, tracking along appropriate z scores. This growth continued even in patients without ongoing immunosuppression (Figure 1).

Conclusion: PHT is a transformative approach to valvular replacement and delivers growing heart valves for infants with irreparable valvular disease. Transplanted homografts demonstrate sustained viability and growth with limited, single-agent immunosuppression.