Atrioventricular conduction tissues in univentricular hearts of left ventricular type with absent right atrioventricular connection ('tricuspid atresia').

Abstract

SUMMARYThe atrioventricular conduction tissues in 14 hearts with absence of the right atrioventricular connection ('tricuspid atresia') were studied by serial sectioning. In all cases, the atrioventricular node lay in the floor of the right atrium, posterior to the tendon of Todaro, but in all but one case it extended anteriorly either medial or lateral to the insertion of the tendon in a way not seen in the normal heart. The common bundle frequently arose from the anterior or lateral extensions of the node and, after penetration of the central fibrous body, came to lie on the right wall of the main ventricular chamber at the point of junction with the septum separating this chamber from the outlet chamber. In all but 3 cases, branching of the bundle occurred posterior to the outlet foramen. The distribution of the left bundle characteristically favoured the posterior part of the main chamber and the right bundle passed inferior to the outlet foramen to ramify in the trabecular zone of the outlet chamber.Although these findings differ in some respects from those previously described in univentricular hearts with an outlet chamber and 2 atrioventricular valves, we believe that they are consistent with our view that the majority of hearts with absence of the right atrioventricular connection come within the category of the univentricular heart.In recent years, the outlook for patients with atresia or absence of the right atrioventricular orifice has been improved by the use of corrective surgical procedures such as that developed by Fontan and Baudet (1971). During such procedures, the conducting tissue may be at risk during closure of the atrial septal defect, during closure of the outlet foramen, and when enlargement of the outlet foramen is required because the aorta arises from the outlet chamber. The disposition of conducting tissue also has implications for the morphology and classification of the anomaly.Anderson and his colleagues (1977) have expressed the view that atresia (or absence) of the right atrioventricular orifice is, in most cases, associated with the ventricular morphology of a univentricular heart, usually with an anterior rudimentary chamber. They recognised, however, that in a small num-1RHA is supported by the Joseph Levy Foundation together with the British Heart Foundation.

Atresia of the right atrioventricular orifice with atrioventricular concordance.

“…In the cases presently described, the atrioventricular bundle is related to the inlet septum in a fashion directly comparable to that seen in isolated ventricular septal defect with atrioventricular concordance. In contrast, in examples of 'tricuspid atresia' with absent right atrioventricular connection, the ventricular conducting tissues are arranged as in univentricular hearts of left ventricular type with 2 atrioventricular valves ('single ventricle with outlet chamber') (Dickinson et al, 1979 Fig. 5.…”

Systemic ventricular morphology-associated increased QRS duration compromises the ventricular mechano-electrical and energetic properties long-term after the Fontan operation

“…In addition, an immature and/or abnormally developed conduction system, common in patients with single ventricle complexes [18][19][20], may contribute to the electrical conduction delay thereby prolonging the SV action potential. These possibilities emphasize the importance of early elimination of ventricular volume overload and hypoxia to prevent deterioration of SV function, at least, that component arising through MEI problems in patients with single ventricular physiology, especially in non-LV SV patients.…”

Development of the Myocardium of the Atrioventricular Canal and the Vestibular Spine in the Human Heart

“…This condition resembles the heart in the 6th week of development. The normal closure of the primary atrial foramen and relatively normal position of the atrioventricular node 33 indicate that development of the vestibular spine is normal in the setting of tricuspid atresia. Incomplete expansion of the ventricular connections of the canal musculature produces overriding and straddling of the tricuspid valve, intermediate between double-inlet and the normal heart.…”