The Mesenchymal Cap of the Atrial Septum and Atrial and Atrioventricular Septation

In this publication, dedicated to Professor Robert H. Anderson and his contributions to the field of cardiac development, anatomy, and congenital heart disease, we will review some of our earlier collaborative studies. The focus of this paper is on our work on the development of the atrioventricular mesenchymal complex, studies in which Professor Anderson has played a significant role. We will revisit a number of events relevant to atrial and atrioventricular septation and present new data on the development of the mesenchymal cap of the atrial septum, a component of the atrioventricular mesenchymal complex which, thus far, has received only moderate attention.

Genetic testing for atrioventricular septal defect

Atrioventricular septal defect (AVSD) is a congenital heart defect characterized by a shared atrioventricular junction coexisting with deficient atrioventricular septation. The main morphological characteristic of AVSD is a common atrioventricular canal. The prevalence of AVSD is estimated at 0.31/1000 live births and is higher among subjects with PTPN11 mutations. ASD may have autosomal dominant or autosomal recessive inheritance. This Utility Gene Test was prepared on the basis of an analysis of the literature and existing diagnostic protocols. It is useful for confirming diagnosis, as well as for differential diagnosis, couple risk assessment and access to clinical trials.

Atrioventricular septal defect with coexisting tricuspid atresia

We describe two infants having an atrioventricular septal defect in the setting of a double inlet atrioventricular connection, but with patency of the left-sided valvar orifice and an imperforate right-sided valvar component, and a further case with atrioventricular septal defect and an imperforate Ebstein's malformation, all producing the haemodynamic effect of tricuspid atresia. We make comparisons with the arrangement in trisomy 16 mice, in whom deficient atrioventricular septation is seen at times with the common atrioventricular junction exclusively connected to the left ventricle, a situation similar to that seen in two of our infants. We also review previous reports emphasising the important theoretical implication of the findings despite their rarity.

Surgical Anatomy of Atrioventricular Septal Defect

This review aims to describe the anatomic spectrum of hearts classified with the collective term atrioventricular septal defect. Despite their anatomical variety, hearts with the stigmata of atrioventricular septal defect share the characteristic feature of a common atrioventricular junction guarded by a 5-leaflet valve. The lack of normal atrioventricular septation makes the aorta un-wedged, resulting in an elongated outlet length on the left ventricular surface (known as inlet-outlet disproportion). The major determinant of anatomic variations is the relationship of the bridging leaflets to the septal structures. This important relationship determines not only the level of intracardiac shunting (interatrial only, interventricular only, or both) but also the propensity for left ventricular outflow tract obstruction. Furthermore, the location of the atrioventricular node, which is posteroinferiorly displaced from the tip of the triangle of Koch, is also affected by this relationship. Understanding the cardiac anatomy in this malformation is an absolute prerequisite for successful surgery, and should be facilitated by recognizing the fundamental nature of the morphology.

The morphology and diagnosis of atrioventricular septal defects

SummaryIn this review, we discuss and describe those features which distinguish hearts with abnormal atrioventricular septation from the normal heart. The hearts, best described as atrioventricular septal defects, are unified by having a common atrioventricular junction guarded by a valve having five leaflets. The left component has three leaflets and cannot be interpreted in terms of a cleft in a normal mitral valve. The papillary muscles supporting this valve are also markedly dissimilar from the arrangement seen in normal hearts. The subaortic outflow tract is displaced superiorly compared to the normal heart, and is no longer wedged between the left valve and the septum. There is marked discrepancy in the inlet and outlet lengths of the ventricular mass, these dimensions being equal in hearts with normal atrioventricular septation. Although having the above features in common, atrioventricular septal defects show anatomic variations related to the arrangement of the bridging leaflets and their relationship to the septal structures. There may be a common valvar orifice or separate right and left orifices. The anatomic potential for shunting may be at atrial or ventricular levels, or both. Rarely, the septal structures may be intact. Other important features include ventricular dominance, the left ventricular outflow tract, and the disposition of the atrioventricular conduction tissues.

Atrioventricular septal defect—the need for a flexible surgical approach in a lesion with markedly individual features

Hearts with biventricular connections and deficient atrioventricular septation are readily recognizable from their characteristic morphology.1As yet, however, there is still no consensus on precisely what to call them,2how to categorize them, and, perhaps most importantly, how to approach their surgical repair.