Growing Heart Valves in Congenital Cardiac Surgery: Mechanisms and Considerations for Tissue-Engineered Heart Valves, Noncryopreserved Homografts, and Partial Heart Transplantation

Abstract: Heart valve abnormalities are present in 30% of congenital heart defects. Additionally, there are acquired conditions like rheumatic heart disease. They often require surgery, and in complex cases, valve replacement becomes unavoidable. The current valve replacement options, either mechanical, bioprosthetic, homografts, or autografts, lack key properties for pediatric patient needs: availability, durability, and the ability to grow. Our goal is to review 2 clinically relevant innovations: tissue-engineered heart valves (TEHVs) and partial heart transplantation (PHT). We conducted searches in electronic databases covering the past 25 years using the terms “partial heart transplantation,” “tissue-engineered heart valves,” and their combinations. Decellularized pulmonary homografts outperform cryopreserved homografts and bovine jugular vein conduits in pulmonary valve replacement, showing less stenosis and no infective endocarditis. The European Clinical Study for the Application of Regenerative Heart Valves trial confirmed decellularized pulmonary homograft safety, demonstrating 97.5% freedom from explantation at 5 years. Decellularized aortic homografts showed excellent 97.8% 5-year survival and low endocarditis rates, though increases in transvalvular gradient and regurgitation occurred. Partial heart transplantation uses living valves from donor hearts and accommodates somatic growth. Postoperative immunosuppression in PHT is required but may be limited, as children and valve tissues may possess immune privilege, as evidenced by limited valve injury even in failed orthotopic heart transplants. In a pilot study of 19 infants, with a median follow-up of 26 weeks, increases in annular diameter and leaflet length were observed. Both PHT and TEHVs are promising valve replacement options. While PHT provides a growth-adaptive capability, TEHVs hold the potential for off-the-shelf solutions with minimal immunogenicity.