Differences in extra-cellular matrix and myocyte homeostasis between the neonatal right ventricle in hypoplastic left heart syndrome and truncus arteriosus

Objective: The right ventricle in hypoplastic left heart syndrome (HLHS) works at systemic pressure and large volume loading before and after first stage palliation. There is a paucity of information regarding the intrinsic characteristics of the right ventricle in HLHS. We studied extra-cellular matrix composition, myocyte homeostasis and gene expression in right ventricular biopsies obtained from patients with HLHS undergoing neonatal first stage palliation and from patients undergoing neonatal truncus arteriosus repair. Methods: Tissue was evaluated using histological and real-time PCR techniques using the truncus group as a comparative group. Mean difference in outcomes between the HLHS and truncus groups was estimated using linear regression models in unadjusted and age-adjusted analyses. Results: Markers of cell proliferation, apoptosis and fibronectin were significantly higher in the right ventricular myocardium of patients with hypoplastic left heart syndrome compared to truncus arteriosus. Type I collagen content and NKX2.5 expression were significantly lower in HLHS than the truncus group. Conclusion: The neonatal right ventricle in HLHS demonstrates a number of intrinsic differences compared to the right ventricle in truncus arteriosus including relative immaturity of the extra-cellular matrix, inappropriately low transcription factor expression and increased myocyte apoptosis.