Rajab, Taufiek Konrad

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.

Despite efforts to improve donor heart allocation policies, geographic disparities, logistical challenges and patient criteria limit organ availability. However, recent surgical innovations offer potential solutions. These include partial heart transplantation and xenotransplantation. Partial heart transplantation is a new procedure with the potential to address several clinical challenges in treating congenital heart defects. Cardiac xenotransplantation involves the transplantation of genetically modified porcine hearts into humans, offering a potential solution to the shortage of donor organs. Although immunologic barriers and ethical concerns remain, ongoing research aims to mitigate the risks and optimize outcomes, providing hope for patients in need. These innovative surgical approaches offer promising avenues for addressing the critical shortage of donor hearts and with ongoing research, may hold the potential to revolutionize heart transplantation, and improve outcomes for patients facing terminal heart failure.