Low incidence of atrial septal defects in nonmammalian vertebrates

Abstract

The atrial septum enables efficient oxygen transport by separating the systemic and pulmonary venous blood returning to the heart. Only in placental mammals will the atrial septum form by the coming-together of the septum primum and the septum secundum. In up to one of four placental mammals, this complex morphogenesis is incomplete and yields patent foramen ovale. The incidence of incomplete atrial septum is unknown for groups with the septum primum only, such as birds and reptiles. We found a low incidence of incomplete atrial septum in 11 species of bird (0% of specimens) and 13 species of reptiles (3% of specimens). In reptiles, there was a trabecular interface between the atrial septum and the atrial epicardium which was without a clear boundary between left and right atrial cavities. In developing reptiles (four squamates and one crocodylian), the septum primum initiated as a sheet that acquired perforations and the trabecular interface developed late. We conclude that atrial septation from the septum primum only results in a low incidence of incompleteness. In reptiles, the atrial septum and atrial wall develop a trabecular interface, but previous studies on atrial hemodynamics suggest this interface has a very limited capacity for shunting. evolution, heart, patent foramen ovale, septationThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

TheTale‐TellHeart: Evolutionary tetrapod shift from aquatic to terrestrial life‐style reflected in heart changes in axolotl (Ambystoma mexicanum)

“…Evolution of the ability to breathe air goes together with the establishment of pulmonary circulation and the separation of the oxygen‐rich and oxygen‐poor blood within the heart 42,43 . This strategy formed the success of terrestrial life‐style in ectothermic tetrapods 44 .…”

“…Evolution of the ability to breathe air goes together with the establishment of pulmonary circulation and the separation of the oxygen-rich and oxygen-poor blood within the heart. 42,43 This strategy formed the success of terrestrial life-style in ectothermic tetrapods. 44 Respiration in amphibians comes in several different modes: cutaneous respiration (skin breathing), gill respiration, and lung respiration, and even combinations of these.…”

Cor Triatriatum Dexter Associated with an Ostium Primum Atrial Defect and Left-Sided Opening of the Coronary Sinus in a Stillborn Fetus

“…Most cases with known etiology are believed to be caused by genomic abnormalities, including mutations in genes important for heart development such as transcription factors [ 29 ] or structural heart genes [ 30 ], but also maternal environmental factors such as diabetes [ 31 ], a high-fat diet [ 32 ], ethanol abuse [ 33 ] or exposure to other teratogens including prenatal viral infections (recently reviewed in [ 28 ]). The defects of atrial septation, as noted in our case, are far more common in mammals than in other vertebrates, probably due to its higher complexity with primary and secondary septa [ 34 ].…”

Heart morphology during the embryonic development ofPodocnemis unifilisTrosquel 1948 (Testudines: Podocnemididae)

“…The early cardiac development seen in reptiles (Hanemaaijer et al, 2019; Jensen, Moorman, & Wang, 2014; Jensen, van den Berg, et al, 2013; Jensen, Wang, et al, 2013) is similar to that of other amniote vertebrate groups, including birds and mammals (Jensen, Wang, & Moorman, 2019). Vertebrates share some events during cardiogenesis, such as a looping or folding process of the heart tube responsible for the positioning of future heart chambers (Männer, 2009), the formation of septa and valves by cushioned mesenchymal structures or atrioventricular endocardial cushions (Deepe et al, 2020), and atrial septation by a single septum primum or first septum covered by a mesenchymal cap and dorsal mesenchymal protrusion (Jensen, Joyce, et al, 2019; Jensen, Wang, & Moorman, 2019).…”