Expanding the Donor Pool in Pediatric Heart Transplant with a Novel 3D Technique

Background: Heart transplantation (HTx) is the ultimate medical treatment for end stage heart failure (HF); however, the donor pool remains limited, especially for pediatric patients, due to size mismatch between donor and recipient. Both excessively under and oversized grafts can lead to poor surgical outcomes. A donor to recipient body weight ratio (DRBW) is clinically used to indirectly predict size. Retrospectively, at a collaborating pediatric hospital, the DRBW range has been 0.7 and 4.0; this range is wider than most current literature. Unfortunately, the DRBW is an indirect and possibly imprecise measurement technique. It is hypothesized that a novel 3D virtual transplant tool will better predict size matching. Methods: A healthy heart library was developed from 3D reconstructions of CT/MR data of hearts from patients weighing less than or equal to 22.5 kg and determined to have morphologically normal hearts. A linear fit model for heart volume was derived. This model, along with pre HTx heart volume, was then used retroactively to predict the ‘ideal’ donor heart volume range and donor weight for 3 infant patients. Pre and post HTx scans of these patients were also reconstructed and compared to the predicted ‘ideal’ hearts. Results: A linear regression model between healthy heart volume body weight achieved a R2=0.983. The model determined an ‘ideal’ donor volume that was outside of the the typical donor range for a recipient with cardiomyopathy. Comparing heart volumes pre and post HTx, along with donor heart volume pre HTx, suggests oversized grafts shrunk and undersized grafts grew over a six month period. Conclusions: 3D reconstructions have great potential to compliment current HTx pre-procedural planning mechanisms. In particular the healthy heart library has potential to improve matching between donors and HTx recipients. The additional findings with regards to the graft size changes between pre and post HTx agree with the “shrink-and-grow” phenomena found in current HTx literature and may suggest the acceptable HTx DBWR is too limiting as the sole donor selection criteria.