Morphology of the atrioventricular valve in asplenia syndrome: A peculiar type of atrioventricular canal defect.

The high risk of atrioventricular (AV) valve regurgitation is a major point of concern in the natural history of patients with atrioventricular canal defect (AVCD) and asplenia syndrome (AS). The morphology of the common AV valve in patients with AVCD and AS was therefore studied and compared with the anatomy of patients with AVCD but with atrial situs solitus. We compared the anatomic features of hearts with common AV valve (ventricular loop; AV valve alignment on ventricles; number of leaflets; number and morphology of papillary muscles and relationship of the bridging leaflets with the ventricular septum) in the hearts of 33 patients with AVCD and asplenia syndrome (Group 1) with those of 44 patients with common AV valve, complete AVCD, and atrial situs solitus (Group 2). Hearts featuring asplenia syndrome showed a significantly higher occurrence of anomalies of the ventricular loop (p < .0001), right ventricular dominance (p < .01), and a reduced number of valvular leaflets and papillary muscles (p < .0005). On the contrary, hearts with situs solitus of the atria showed a significantly higher frequency of balanced ventricles (p < .0001) and a common AV valve with five leaflets and five papillary muscles (p < .000001). These data suggest that AVCDs in association with asplenia syndrome present morphologic peculiarities that may be considered as the substrate for the abnormal regurgitation. Recognizing the presence of these features could be of great value for the planning of a specific surgical treatment. These anatomic differences support the hypothesis of a genetic heterogeneity of AVCDs.