Prenatal ethanol exposure impairs the conduction delay at the atrioventricular junction in the looping heart

The etiology of ethanol-related congenital heart defects has been the focus of much study, but most research has concentrated on cellular and molecular mechanisms. We have shown with optical coherence tomography (OCT) that ethanol exposure led to increased retrograde flow and smaller atrioventricular (AV) cushions compared with controls. Since AV cushions play a role in patterning the conduction delay at the atrioventricular junction (AVJ), this study aims to investigate whether ethanol exposure alters the AVJ conduction in early looping hearts and whether this alteration is related to the decreased cushion size. Quail embryos were exposed to a single dose of ethanol at gastrulation, and Hamburger-Hamilton stage 19-20 hearts were dissected for imaging. Cardiac conduction was measured using an optical mapping microscope and we imaged the endocardial cushions using OCT. Our results showed that, compared with controls, ethanol-exposed embryos exhibited abnormally fast AVJ conduction and reduced cushion size. However, this increased conduction velocity (CV) did not strictly correlate with decreased cushion volume and thickness. By matching the CV map to the cushion-size map along the inflow heart tube, we found that the slowest conduction location was consistently at the atrial side of the AVJ, which had the thinner cushions, not at the thickest cushion location at the ventricular side as expected. Our findings reveal regional differences in the AVJ myocardium even at this early stage in heart development. These findings reveal the early steps leading to the heterogeneity and complexity of conduction at the mature AVJ, a site where arrhythmias can be initiated.NEW & NOTEWORTHY To the best of our knowledge, this is the first study investigating the impact of ethanol exposure on the early cardiac conduction system. Our results showed that ethanol-exposed embryos exhibited abnormally fast atrioventricular conduction. In addition, our findings, in CV measurements and endocardial cushion thickness, reveal regional differences in the AVJ myocardium even at this early stage in heart development, suggesting that the differentiation and maturation at this site are complex and warrant further studies.

Congenital discrete subaortic stenosis in pregnancy: case report and literature review

Today's growing numbers of pregnant patients with congenital heart defects presents challenges for cardiologists treating adult patients. The case is presented of a 19-year-old woman who was admitted with a threatened miscarriage in the third trimester and was diagnosed with an incomplete atrioventricular canal, cleft mitral valve with severe regurgitation, and severe congenital subaortic stenosis caused by a subaortic membrane. She was managed conservatively, delivered via cesarean section, and then underwent surgical repair of all defects with good outcome. Here, a review is provided of the literature on the natural course, complications, and treatment strategies of subaortic stenosis, together with a summary of recommendations for the management of the condition.

Complete atrioventricular canal in a dog

This report details a case of complete, type A atrioventricular (AV) canal, also called complete endocardial cushion defect, in a young dog. Complete AV canal is classified as three types: A, B or C depending on the degree of linkage between common AV valve and ventricular chambers. Despite the defect this dog, which did not undergo surgical treatment, remains in ISACHC class Ib 19 months after the initial diagnosis.