Open Access

ARTICLE

Characterization of Malalignment between Atrial and Ventricular Septa in Overriding/Straddling Tricuspid and Mitral Valves

Mika Saito^1,2, Dragulescu Andreea^1,2, Shi-Joon Yoo^1,2,3,*

1 The Labatt Family Heart Centre, The Hospital for Sick Children, University of Toronto, Toronto, Canada
2 Division of Cardiology, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Canada
3 Department of Diagnostic Imaging, The Hospital for Sick Children, University of Toronto, Toronto, Canada

* Corresponding Author: Shi-Joon Yoo. Email:

Congenital Heart Disease 2021, 16(1), 1-16. https://doi.org/10.32604/CHD.2021.011694

Received 05 May 2020; Accepted 12 October 2020; Issue published 23 December 2020

Abstract

Objective: Overriding/straddling of an atrioventricular valve is a consequence of atrial-ventricular septal malalignment. We sought to characterize the malalignment by analogizing it to a flap-door and using structured approach. Methods: The echocardiograms and magnetic resonance images of 35 patients with overriding/straddling tricuspid or mitral valve were evaluated to assess the following modifiers; the malaligned part of the septum, the reference structure, and the mechanism, direction and severity of malalignment. Results: The pathology included classic overriding tricuspid valve in 15, classic overriding mitral valve in 12, and overriding tricuspid valve with left juxtaposition of atrial appendages in 8. In classic overriding tricuspid valve, the ventricular septum was hinged to the anterior interventricular groove and its insertion to the posterior interventricular groove was displaced toward the right ventricle. The VSD primarily involved the inlet but also extended toward the anterior interventricular groove. In classic overriding mitral valve, the ventricular septum was hinged to the posterior interventricular groove and crux cordis. Its insertion to the anterior interventricular groove was displaced toward the left ventricle. The VSD primarily involved the anterior part but also extended toward the inlet. Overriding tricuspid valve with left juxtaposition of atrial appendages had a mild degree of malalignment with displacement/rotation of the atrioventricular junction. Evenly spaced short-axis images were most helpful in characterizing the pathology. Conclusions: Overriding/straddling atrioventricular valves can be easily understood by analogizing the atrial-ventricular septal malalignment to a flap-door and describing the pathology in a structured manner. Contrary to what has previously been known, the VSD is not limited to the inlet or outlet part of the ventricular septum.

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