Semilunar valves in pediatric orthotopic heart transplants grow at a slower rate than controls

Background: Partial heart transplantation is a novel approach to deliver a growing donor valve in pediatric recipients needing valve replacements. Objective data on the rate of growth of semilunar valves in patients following orthotopic heart transplantation (OHT) is necessary to set expectations for partial heart transplant semilunar valve growth. Methods: A retrospective cohort study was performed, which included twelve infants who underwent OHT and twelve controls with ventricular septal defects (VSD). Semilunar valve annulus absolute dimension over serial echocardiograms was recorded, Z-scores were calculated, and mixed-effects models were applied to the absolute dimension (mm) and scaled dimension (Boston Z-score). Results: Aortic and pulmonary valve annuli in OHT patients grow. There is a downward trend in aortic valve annulus Z-score over time for OHT patients compared to population norms and controls with VSDs (difference in slopes: -0.119 Z-score/y, 95% CI: [-0.209, -0.029], p = 0.011); there is a non-significant difference for the pulmonary valve annulus (difference in slopes: -0.067 Z-score/y, 95% CI: [-0.155 0.022], p = 0.140). Conclusions: Semilunar valves in pediatric OHT patients grow at a slower rate than controls. There was no semilunar valve obstruction in our cohort. While the described difference in valve growth may not be clinically significant for pediatric OHT recipients, these growth rates inform the anticipated growth trajectory for the partial heart transplant graft.