Unguarded mitral orifice, mirror-imaged atrial arrangement, and discordant atrioventricular connections

Abstract

We report two autopsy proven cases of unguarded mitral orifice associated with mirror-imaged atrial arrangement, discordant atrioventricular connections, double outlet right ventricle, pulmonary valvar stenosis or atresia, and atrialisation of the morphologically left ventricle. The morphologically left atrioventricular junction was devoid of valvar leaflets, and there was no tension apparatus within the ventricle. To the best of our knowledge, this is the first description of this rare cardiac malformation.

A potential new constellation of defects: Unguarded mitral orifice associated with double-outlet right ventricle {I, D, D} and pulmonary atresia/stenosis

“…atrioventricular discordance associated with DORV and pulmonary atresia in situs inversus. Unexpectedly, all 4 cases, including ours, were male, and all had the identical, above-mentioned segmental set and alignment (DORV {I, D, D}) and similar associated malformations (pulmonary atresia or stenosis) [1,2]. Therefore, these limited case series might imply that the consistent association of 2 uncommon anomalies-UMO and DORV {I, D, D} with pulmonary atresia/stenosisrepresents a previously unsuspected causal relation and possibly constitutes a new constellation of defects with unique clinical implications.…”

“…The only previously reported cases in the English literature were 2 autopsy cases described by Yasukochi et al [1] in 1999 and 1 case reported by Earing et al [2] in 2003. Notably, all 4 cases, including ours, were male, and all had the same segmental set and alignment of DORV {I, D, D} and similar associated malformations of pulmonary atresia or stenosis (Table 1) [1,2]. Although the third case had no identifiable spleen, mirror-image atrial sidedness and systemic veins were present, which probably basically indicated atrial situs inversus [2].…”

“…

Unguarded mitral orifice (UMO) is an extremely rare congenital cardiac anomaly characterized by the complete absence of mitral valvar leaflets and tensor apparatus (chordae tendineae and papillary muscles) at the mitral annulus and severe thinning of the left ventricular (LV) free wall [1,2]. To our knowledge, only 3 cases have been reported [1,2].

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“…To our knowledge, only 3 cases have been reported [1,2]. We report here the possible fourth case occurring in the setting of double-outlet right ventricle (DORV) {I, D, D} (visceroatrial situs inversus [I], D-loop ventricles [D], and D-malposition of the great arteries [D]) associated with pulmonary atresia, i.e.…”

“…This process is accompanied by invagination of the atrioventricular sulcus [4]. To explain UMO, Yasukochi et al [1] hypothesized that abnormality in undermining of the myocardium could be introduced by either maldevelopment of the mesenchymal tissue or apoptosis of the myocardial cells of the LV. If this happens before the valvar leaflets separate from the embryonic ventricular myocardium, the valvar leaflets in the afflicted ventricle could fail to delaminate and the ventricular wall becomes thinned.…”