Edema of the collar zone
Causes of thickening of the collar space. The collision space for heart defects
Identify narrowing of the aortic isthmus in combination with an increase in the diameter of the aorticvalve and the expansion of the ascending arch of the aorta in these embryos makes it possible to suggest that it is the narrowing of the aortic isthmus that is the primary link in the formation of a complex of pathological disorders. The complex of these changes can cause an increase in the collar space, leading to subcutaneous edema as a result of hyperperfusion of the head and neck tissue.
With increasing gestational age the diameter of the aortic isthmus increases faster than the diameter of the aorticvalve and distal part of the ductus arteriosus. In this connection, the degree of expression of the hemodynamic effects described above can gradually decrease. This hypothesis can explain the spontaneous reduction in the size of the collar zone from 80% to 30%, which is found in fruits with trisomy 21 as the pregnancy progresses (from 11 to 20 weeks).
This phenomenon also explains the transient increasecollar space in fruits with an euploid set of chromosomes. A group of these same scientists in subsequent studies evaluated the structure of the heart and major vessels in fruits with a normal karyotype, in which an increase in the collar space was recorded. In 19 out of 21 cases, the anomalies were confirmed. The most frequently observed aortic narrowing in the isthmus region and directly above the aortic valve, which was different from the condition with trisomy 21, in which the narrowing of the isthmus was combined with an increase in the diameter of the aortic valve.
Thus, the results of this of work suggest that the increase in collar space is observed in the presence of cardiac abnormalities and violations of the development of major vessels, even if the fetus does not have a chromosomal pathology.
J.A. Hyett et al. after conducting the most extensive study,analyzed the incidence of heart disease or major vessels in 112 fetuses with trisomy 21,18, 13, and karyotype 45, X0, in whom the diagnosis was suspected after revealing the expansion of the collar space and confirmed by biopsy of the chorionic villi. With trisomy 21, septal defects were most frequently observed, with trisomy 18 - ventricular septal defects and / or multiple valve anomalies, with trisomy 13 - septal defects, valve anomalies, and constriction of the isthmus of the aorta or arterial duct and in karyotype 45, X0 - marked stenosis all divisions of the aortic arch. In the presence of an increase in the collar space in fruits with chromosomal aberrations, narrowing of the aortic isthmus was more pronounced than in those with normal karyotype.
The obtained results testify in favor of hypotheses. according to which narrowing of the aortic isthmus is the main pathogenetic mechanism causing an increase in the collar space.
A. Matias et al. described three cases of diagnostic expansioncollar space in terms of 12-13 weeks of pregnancy in 3 fruits with trisomy 13, 18 and 21. With Doppler ultrasound, a pathological type of venous return was recorded. Severe hemodynamic changes were manifested in the form of high-speed retrograde blood flow in the inferior vena cava, as well as very low rate or reverse flow during the atrial contraction phase and the appearance of the so-called dicrotic pulsating type of blood flow in the cord vein.
These results also confirm that the collar space is an early marker of the presence of heart defects in the fetus.