Defecto septal atrial. Estudio morfopatológico, embriológico / Atrial septal defect. A morphopathological and embryological study

To contribute to a better understanding of the morphopathology of atrial septal defects (ASD), we describe and classify topographically a series of hearts obtained from necropsies. We performed an anatomo-embryological correlation to gain insight on the pathogenesis of this type of congenital heart disease. Seventy-one hearts with ASD and twenty-three normal hearts with patent foramen ovale from the collection at the Instituto Nacional de Cardiologia lgnacio Chavez were studied morphologically; segmental sequential analysis was used. The topography of the interatrial septum was determined on the basis of the structures related to it in order to classify the ASD. The FS area was projected on the right septal surface using pins. To stablish the anatomo-embryological correlation, the ASD's anatomy was compared with the embryological processes that take place in atrial septation. The most frequent ASD was the OO type (FS) with 64.78%, followed by common atrium, true FS, FP, superior and inferior sinus venosus, types each one with 2.81% and one coronary sinus venosus type (1.40%). The FS area was projected below the superior vena cava. The morphologically and topographically knowledge of atrial septal defect is useful to interpret the imaging studies of this cardiopathy and is basic for the surgeon and the interventionist cardiologist. Abnormal apoptosis and retarded developmental growth are proposed as pathogenic mechanisms.

[Atrial septal defect. A morphopathological and embryological study]. / Defecto septal atrial. Estudio morfopatológico, embriológico.

To contribute to a better understanding of the morphopathology of atrial septal defects (ASD), we describe and classify topographically a series of hearts obtained from necropsies. We performed an anatomo-embryological correlation to gain insight on the pathogenesis of this type of congenital heart disease. Seventy-one hearts with ASD and twenty-three normal hearts with patent foramen ovale from the collection at the Instituto Nacional de Cardiologia lgnacio Chavez were studied morphologically; segmental sequential analysis was used. The topography of the interatrial septum was determined on the basis of the structures related to it in order to classify the ASD. The FS area was projected on the right septal surface using pins. To stablish the anatomo-embryological correlation, the ASD's anatomy was compared with the embryological processes that take place in atrial septation. The most frequent ASD was the OO type (FS) with 64.78%, followed by common atrium, true FS, FP, superior and inferior sinus venosus, types each one with 2.81% and one coronary sinus venosus type (1.40%). The FS area was projected below the superior vena cava. The morphologically and topographically knowledge of atrial septal defect is useful to interpret the imaging studies of this cardiopathy and is basic for the surgeon and the interventionist cardiologist. Abnormal apoptosis and retarded developmental growth are proposed as pathogenic mechanisms.

Behavior of septum primum mobility in third-trimester fetuses with myocardial hypertrophy.

OBJECTIVES: The mobility of the septum primum (SP) in the fetus is a diastolic phenomenon and could be related to left atrial pressure. We studied the linear displacement of the SP in the left atrium in fetuses of diabetic mothers (FDM) with and without septal hypertrophy (SH) and in normal fetuses of normoglycemic mothers. In this study we set out to test the hypothesis that the linear displacement of the SP flap valve is less marked in fetuses with SH than in those without SH. METHODS: The ratio between the linear displacement of the flap valve and the left atrial diameter (excursion index (EI)) was compared in ten FDM with SH, eight FDM with normal septal thickness and eight normal fetuses of non-diabetic mothers. Atrioventricular flow velocities were also compared in the three groups. RESULTS: Comparison of the three groups showed that in FDM with SH, the mean EI was 0.36 +/- 0.09, in FDM without SH it was 0.51 +/- 0.09 (P = 0.001) and in the control fetuses it was 0.49 +/- 0.12 (P = 0.03). There was a significant negative correlation between septal thickness and EI in FDM with SH. There was no correlation between septal thickness and atrioventricular flow velocities. CONCLUSION: Mobility of the SP in FDM with SH is reduced and there is an inverse correlation between the linear displacement of the SP and septal thickness. These findings may be related to changes in left ventricular diastolic function secondary to myocardial hypertrophy.

Myocardial interatrial septum loses its epithelial organization by mesenchymal influence. Structural and ultrastructural study.

During atrial septation, the septum primum fuses with the atrioventricular endocardial cushions and myocardial-mesenchymal interactions occur. In order to evaluate the cellular events that take place during this particular interaction a structural, ultrastructural and histochemical study was performed. Our findings indicate that from the fourth day of development, the distal myocardium of the interatrial septum, which interacts with mesenchymal tissue, loses its appearance of an epithelial sheet and becomes a loosely organized tissue. The distal myocytes of the interatrial septum which get progressively separated show features of migratory cells, the final localization of which is the mesenchymal tissue of the adjacent endocardial cushions. These tissue changes involve basal membrane disruption, reduction in the number of desmosomes and intercalated discs with the subsequent appearance of large intercellular spaces between myocytes, myofibrillar disarrangement and acquisition by myocytes of a secretory phenotype characterized by numerous cytoplasmic vesicles. These events occur in a similar way in the atrioventricular canal, where a myocardial-mesenchymal interaction also occurs. In both regions the mesenchymal endocardial cushions and its associated extracellular matrix seem to direct the dissociation of the myocardial tissue and the subsequent migratory cellular behaviour of the interacting myocytes. This is an interesting, and little known, example of a cellular phenotypic transformation during cardiac development.

[Prenatal echocardiographic study of septum primum redundancy and its relationship to the genesis of atrial extrasystole in the fetus]. / Estudo ecocardiográfico pré-natal da redundância do septum primum e sua relação com a gênese de extra-sístoles atriais no feto.

PURPOSE: To test the hypothesis that the redundancy of the septum primum is more pronounced in fetuses with atrial premature beats than in normal fetuses. METHODS: Twenty-five consecutive fetuses with atrial premature beats detected by prenatal echocardiography as the sole alteration at a mean gestational age of 34 +/- 3.3 (26 to 38) weeks and a mean maternal age of 27 +/- 6.5 (18 to 39) years made up the study group. The control group was formed by 50 consecutive fetuses without rhythm disturbances and normal prenatal echocardiography, examined at a mean gestational age of 33.9 +/- 3 (26 to 39) weeks and a mean maternal age of 31 +/- 5.8 (18 to 43) years. A redundancy index (RI) was obtained as a ratio between the maximal septum primum excursion and the maximal left atrium diameter during atrial diastole, at the 4-chamber projection. Statistical analysis utilized the unpaired Student-Fisher's "t" test. RESULTS: The RI in the study group varied from 0.50 to 1.00 (mean = 0.758 +/- 0.127) and in the control group in ranged from 0.29 to 0.67 (mean = 0.449 +/- 0.080). These differences were statistically significant for p < 0.0001. CONCLUSION: Septum primum is more redundant in fetuses with atrial premature beats than in those with normal regular rhythm. Although it is still speculative that this feature may have a cause-effect relationship, the measurement of the RI during routine fetal echocardiography may allow detection of a potential risk factor FOR developing atrial arrhythmias.

[Juxtaposition of the atria]. / Yuxtaposición de las orejuelas.

Left juxtaposition of atrial appendages is an anomaly of their origin and position which is associated with a high incidence of complex congenital heart defects. We studied six cases of juxtaposed right atrial appendages. They emerged from the anterior wall adjacent to the atrial septum and were situated to the left of the origin of the great arteries. Associated congenital heart defects were: single outlet, right ventricular hypoplasia, absent right atrioventricular connection, ventricular and atrial septal defects and pulmonary outflow obstruction. Other abnormal morphological features present were anatomically corrected malposition of the great arteries, bilateral infundibulum and right aortic arch. Although the association of these malformations with juxtaposed atrial appendages does not per se constitute a syndrome, its presence is an ominous sign of severe cyanotic congenital heart disease which should alert both clinicians and surgeons. There are various possible embryological explanations for the genesis of this malformation. We believe that juxtaposition is the consequence of the ectopic origin of the atrial appendage rudiment, which in the presence of truncal alterations grows behind and to the left of the great arteries.

[Embryologic and anatomic considerations on the normal and pathologic formation of the cardiac septum. I. Interauricular septum]. / Consideraciones embriológicas y anatómicas sobre la septación cardiaca normal y patológica. I. Septum interauricular.

A brief presentation of the normal embryological development of the human interatrial septum is made. The anatomical expression of each of its embryological components is described. Our classification of interatrial septal defect is enriched by their more precise anatomical description and by making a more correct morphogenetic interpretation, based on new information obtained by means of experimental embryology. Emphasis is made that absence of the interatrial septum does not preclude the diagnosis of viscero-atrial situs.

Origin of mesenchymal tissue in the septum primum: a structural and ultrastructural study.

A structural, ultrastructural and histochemical study in chick embryos indicates that the septum primum mesenchymal tissue originate between 3 and 5 days of development and that their origin may be related to an activation of endocardial cells that cover the septum primum. By day 3, endocardial cells display migratory appendages, cell hypertrophy and an increase in secretory and mitotic activity. In later stages (day 4) hypertrophic endocardial cells undergoing division seem to delaminate and translocate toward the subendocardial space to give rise to free mesenchymal-type cells. These results suggest that the endocardium makes up the bulk of the septum primum mesenchymal tissue as has been demonstrated during mesenchymal tissue formation in the atrioventricular canal and outflow tract. Before and during mesenchymal tissue formation an accumulation of extracellular matrix components like proteoglycans can be visualized using tannic acid. These extracellular components might be related to the promotion of cellular events described during endocardial activation. The fusion of the septum primum with the atrioventricular (AV) endocardial cushions which would obliterate the foramen primum, occurs between mesenchymal tissues. Therefore, any alteration in the normal development of these mesenchymal tissues could be related to pathological cases of persistent atrial communications. Light microscopy preliminary observations of embryonic mouse heart indicate that septum primum mesenchymal tissue formation occurs similarly between mouse and chick embryos.