Related Experiment Videos
Embryological observations on the formal pathogenesis of double-outlet left ventricle with a right-ventricular
Insights
Double-outlet left ventricle (DOLV) is a congenital heart defect where both great arteries arise from the left ventricle. This study reveals that a misaligned ventricular septum, not abnormal great artery positioning, causes DOLV in chick embryos.
Area of Science:
- Developmental biology
- Cardiovascular embryology
- Congenital heart defects
Background:
- Double-outlet left ventricle (DOLV) is a complex congenital heart malformation.
- Previous theories attributed DOLV to abnormal embryonic conotruncus development.
- Modern research questions these traditional explanations for DOLV pathogenesis.
Purpose of the Study:
- To investigate the embryological basis of DOLV in a chick fetus model.
- To challenge existing theories on the pathogenesis of double-outlet left ventricle.
- To elucidate the role of ventricular septal alignment in DOLV.
Main Methods:
- Examination of a chick embryo exhibiting double-outlet left ventricle.
- Analysis of the positioning and dimensions of embryonic conotruncus derivatives.
- Detailed assessment of ventricular septum orientation and its relationship to great arteries.
Main Results:
- The embryonic conotruncus derivatives were normally positioned and sized in the studied DOLV case.
- A misaligned ventricular septum, oriented frontally anterior to great artery origins, was identified as the primary anomaly.
- This misalignment resulted in the separation of the right-ventricular infundibulum from the great arteries.
Conclusions:
- DOLV can result from ventricular septal misalignment, challenging prior topogenesis theories.
- Embryonic conotruncus septation involves at least two distinct septa: one for the conus and one for the truncus arteriosus/aortic sac.
- Misalignment of the embryonic conus septal anlagen likely causes the ventricular septal defect leading to this type of DOLV.
Abstract:
The term 'double-outlet left ventricle' (DOLV) denotes congenital heart malformations in which the aorta and the pulmonary trunk both arise entirely or predominantly above the morphologically left ventricle. In the past, the formal pathogenesis of DOLV was explained by an abnormal topogenesis of the origin of the great arteries, which could be caused by an excessive leftward shift of the embryonic conotruncus, or by errors in differential conal growth or absorption. However, modern embryological and pathological research is casting doubt on the validity of these concepts. In the present paper we demonstrate a case of DOLV found in a chick fetus. In this heart the main derivatives of the embryonic conotruncus (right-ventricular infundibulum and proximal portions of the great arteries) principally are in the normal position and of normal dimensions. The anomaly leading to DOLV under these conditions is a misalignment of the ventricular septum. The subarterial portion of the ventricular septum above the crista supraventricularis is not oriented in the normal oblique plane between the pulmonary and aortic valve, but is oriented in a frontal plane anterior to the origin of both great arteries. The consequences of this anomaly are the separation of the right-ventricular infundibulum from the origin of both great vessels (DOLV) and a lack of continuity between the malpositioned portion of the ventricular septum (posterior wall of the right-ventricular infundibulum) and a septum dividing the semilunar valve level. The infundibulum of the right ventricle is derived from the upstream portion of the embryonic conotruncus (conus) whereas the semilunar valves and great arteries are derived from its downstream protion (truncus arteriosus) and the aortic sac. Therefore, our findings suggest that the division of the conotruncus is performed by at least two different septa, one dividing the conus and another dividing the truncus arteriosus and aortic sac. The misalignment of the ventricular septum leading to the presented type of DOLV could result from a misalignment of the septal anlagen of the embryonic conus, the conus ridges. Our findings are discussed with respect to human cases of DOLV and with respect to a recent concept on the septation of the embryonic conotruncus.