Can Two Halves Make a Whole? Technical Feasibility of Isolated Parallel Circulation Heterotopic Cardiac Transplantation: A Pre-clinical Study in 3D and Porcine Models

Background and Objectives: To explore a novel application of heterotopic cardiac transplantation for creating isolated parallel circulations in patients with univentricular pump failure, particularly those with Hypoplastic Left Heart Syndrome or severe one-sided ventricular dysfunction. Methods: The surgical technique was developed using 3D instructional anatomical modeling and subsequently performed in an ex-vivo porcine model (n=3). We assessed the anatomical feasibility of the "parallel" configuration, where the donor and native hearts function independently to support the systemic and pulmonary circuits. Results: Anatomical feasibility was demonstrated in all three porcine preparations. Key surgical maneuvers included extensive mobilization and anterior transposition of the branch pulmonary arteries and pulmonary vein (PV) rerouting to the donor left atrium. Anastomoses remained patent and leak-free under static fluid loading. Conclusions: Heterotopic cardiac transplantation with isolated parallel circulations may offer a novel therapeutic option for patients with complex congenital heart conditions or severe univentricular pump failure who are unsuitable for conventional orthotopic transplantation. This approach could potentially expand the pool of donor hearts available for transplantation and improve outcomes for this challenging patient population. However, further research, including clinical trials, is necessary to assess the safety, efficacy, and long-term outcomes of this innovative technique. This study lays the groundwork for future exploration and could represent a significant advancement in the field of cardiac transplantation. Central Message: This study introduces a pioneering surgical concept of utilizing heterotopic cardiac transplantation to establish isolated parallel circulations in patients with failing single ventricles. Supported by ex vivo simulations and novel anatomical reconstructions, it lays foundational work for potentially expanding donor heart availability and expanding therapeutic options in complex congenital heart disease. Further preclinical and clinical research is necessary to translate this innovative concept into practice.