Myocardial Afterload Is a Key Biomechanical Regulator of Atrioventricular Myocyte Differentiation in Zebrafish

Heart valve development is governed by both genetic and biomechanical inputs. Prior work has demonstrated that oscillating shear stress associated with blood flow is required for normal atrioventricular (AV) valve development. Cardiac afterload is defined as the pressure the ventricle must overcome in order to pump blood throughout the circulatory system. In human patients, conditions of high afterload can cause valve pathology. Whether high afterload adversely affects embryonic valve development remains poorly understood. Here we describe a zebrafish model exhibiting increased myocardial afterload, caused by vasopressin, a vasoconstrictive drug. We show that the application of vasopressin reliably produces an increase in afterload without directly acting on cardiac tissue in zebrafish embryos. We have found that increased afterload alters the rate of growth of the cardiac chambers and causes remodeling of cardiomyocytes. Consistent with pathology seen in patients with clinically high afterload, we see defects in both the form and the function of the valve leaflets. Our results suggest that valve defects are due to changes in atrioventricular myocyte signaling, rather than pressure directly acting on the endothelial valve leaflet cells. Cardiac afterload should therefore be considered a biomechanical factor that particularly impacts embryonic valve development.

Mitral degenerative valve leaflets suspected as primary valvular tumor: a case report

Introduction: Echocardiography plays an important role in the diagnosis of heart disease. However, sometimes misdiagnosis information is also provided. Methods and Results: We report a rare case of preoperative echocardiography misdiagnosed as a primary mitral valvular tumor with severe regurgitation. During the surgery procedure, the true lesion was found to be mitral valve leaflet prolapse due to degenerative mitral valve disease. Conclusions: For individual patient, it may need to combine clinical symptoms and wide use of echocardiography and CT or MRI to make the optimal clinical decision.