Background While fibrosis seems to be prognostic for adverse outcomes in adults with idiopathic dilated cardiomyopathy (IDC), little is known about the prevalence and development of fibrosis in pediatric IDC hearts. We hypothesize there is less activation of fibrosis at a molecular level in pediatric IDC hearts than in the failing adult heart. Methods and Results Pediatric hearts were analyzed histologically to determine the prevalence of fibrosis. Left ventricular tissue from adult and pediatric IDC hearts and adult and pediatric non-failing (NF) hearts were subjected to qRT-PCR to study the expression of important mRNAs that affect fibrosis. We found age-specific differences between IDC and NF hearts in regulation of non-coding galectin 3, Corin, MMP-2, MMP-9, TIMP-2, and TIMP-3. We also found markers that were similarly altered in both adult and pediatric IDC (ST2L, TIMP-1, and TIMP-4). Finally, microRNAs 29a-c were significantly decreased in the pediatric IDC patients. Conclusion Pediatric IDC patients demonstrate age-specific differences in the molecular pathways implicated in fibrosis in the adult heart. At the ultrastructural level the unique gene expression pattern appears to limit fibrosis in the failing pediatric heart.

Objective To evaluate fibrosis and fibrosis-related gene expression in the myocardium of pediatric single ventricle (SV) subjects with right ventricular (RV) failure. Study design Real-time quantitative polymerase chain reaction was performed on explanted RV myocardium of pediatric SV subjects and non-failing controls. Subjects were divided into 3 groups: SV failing (SV-F, RV failure prior to or following Stage I palliation), SV non-failing (SV-NF, infants listed for primary transplant with normal RV function), and Stage III (Fontan or RV failure following Stage III). In order to evaluate subjects of similar age and RV volume loading, SV-F was compared with SV-NF and Stage III was compared with NF RV. Histologic fibrosis was assessed in all hearts. Mann-Whitney tests were performed to identify differences in gene expression. Results Collagen (Col1α, Col3) expression is decreased in SV-F compared with SV-NF (P = .019 and p=0.035, respectively), and is equivalent in Stage III compared with NF RV. Tissue inhibitors of metalloproteinase (TIMPs1, 3 and 4) are down-regulated in Stage III compared with NF RV (p=0.0047, p=0.013 and p=0.013, respectively). Matrix metalloproteinases (MMP2, MMP9) are similar between SV-NF and SV-F, and between Stage III and NF RV. There is no difference in the prevalence of RV fibrosis by histology in SV subjects with RV failure (18%) compared with those with normal RV function (38%). Conclusions Fibrosis is not a primary contributor to RV failure in infants and young children with SV. Additional studies are required to understand whether anti-fibrotic therapies are beneficial in this population.

The window duct is a rare congenital anomaly that is physiologically similar to an aortopulmonary window but is extrapericardial at the distal pulmonary trunk. The diagnosis is challenging, and surgical management is complex. Our patient is the first and the youngest to be reported with successful closure and diagnosed by magnetic resonance imaging.