title: Discordances between the different types of atrial arrangement and the positions of the thoraco-abdominal organs.
abstract: Numerous investigations have addressed the most appropriate anatomical structures to be used for the identification of segmental arrangement ("situs"). Variations from normal have been termed "heterotaxy syndromes". The assumption is frequently made that, in such instances, all the organs in a given individual case follow the same rules for segmental morphology. This leads to confusion. The starting point for cardiac analysis is the structure of the atriums. On this basis, we can define viscero-atrial discordance when, in usual arrangement, mirror imagery, and heterotaxy, the atriums and their appendages are no longer concordant with the remaining thoracic and abdominal organs. With this in mind, we examined a large number of autopsied specimens to identify all possible variations of thoracic structures and abdominal organs relative to atrial arrangement. We analyzed 1100 malformed hearts. Of these, 1046 had usual arrangement with normally situated heart (95%); 10 cases had usual arrangement with right-sided heart (0.90%); 25 showed mirror imagery (2.27%), and 19 were found with heterotaxy (1.72%). There was a total of 54 hearts of usual arrangement with right-sided heart, mirror imagery and heterotaxy, (4.90%) and, amongst them, 17 showed viscero-atrial discordances (31.48%). In those having usual arrangement with right-sided heart, there were 2 cases (20%); 8 in those with mirror imagery (32%); and 7 in heterotaxy (36.8%). In the 1046 cases of usual arrangement with normally situated heart, there were 12 examples of viscero-atrial discordances (1.14%). In all, we found a total of 29 cases of viscero-atrial discordances. Taken together, the discordances are best dealt with by describing separately, in every case of normal or abnormal atrial arrangement, the thoracic structures, the atrial appendages, and the abdominal organs. In the final analysis, the diagnosis of the cardiac arrangement rests on the location and morphology of the atriums and their appendages.
authors.affiliation: Unidad de Estudio de la Patología Cardiovascular del Niño, Instituto de Anatomía Patológica, Universidad Central de Venezuela, Caracas.
authors.forename: I
authors.initials: I
authors.lastname: Machado-Atias
authors.forename: G
authors.initials: G
authors.lastname: Anselmi
authors.forename: I
authors.initials: I
authors.lastname: Machado-Hernandez
authors.forename: C
authors.initials: C
authors.lastname: Febres
mesh_terms: D000015:Abnormalities, Multiple / Q000473:pathology*; D020517:Atrial Appendage / Q000002:abnormalities* / Q000473:pathology; D002102:Cadaver; D006325:Heart Atria / Q000002:abnormalities* / Q000473:pathology; D006801:Humans; D008099:Liver / Q000002:abnormalities / Q000473:pathology; D008168:Lung / Q000002:abnormalities / Q000473:pathology; D012857:Situs Inversus / Q000473:pathology*; D013154:Spleen / Q000002:abnormalities / Q000473:pathology; D014682:Vena Cava, Inferior / Q000002:abnormalities / Q000473:pathology