Transposition of the great vessels pathophysiology: Difference between revisions
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==Pathophysiology== | ==Pathophysiology== | ||
In normal cardiac anatomy, the aorta is positioned posterior and to the right of the main pulmonary artery. | Dextro-TGA- | ||
* In normal cardiac anatomy, the aorta is positioned posterior and to the right of the main pulmonary artery. Aorta being positioned anterior and slightly rightward of the pulmonary artery. These changes cause the aorta to arise from the right ventricle and the pulmonary artery from the left ventricle (ventriculoarterial discordance). | |||
* In Uncorrected D-TGA the systemic and pulmonary circulations are parallel circuits which means that the deoxygenated systemic venous blood comes to the right ventricle and inplace of going to the lungs, drains back to the systemic circulation via the aorta. Similarly, oxygenated pulmonary venous blood is recirculated to the lungs via the pulmonary artery. | |||
* This parallel circulation is incompatible to life. | |||
* For a child with dextro-TGA to survive, a communication between the two parallel circuits is necessary. | |||
* Various connections that allow mixing in these patients are: patent foramen ovale, ventricular septal defect, atrial septal defect,patent ductus arteriosus or the bronchopulmonary collateral circulation. | |||
** Ventricular septal defect (VSD) occurs (in about 50%) of patients with D-TGA. Patients with a VSD may have other cardiac anomalies like pulmonary stenosis or atresia, overriding of atrioventricular valve, and coarctation of aorta. | |||
** Left ventricular outflow tract obstruction is common in D-TGA and is present in up to 25 percent of patients. | |||
Physiology in-utero | |||
The fetus circulation in-utero is different compared to the extra-uterine circulation. The fetus tolerates the in-utero circulation of D-TGA without much difficulty. Oxygen-rich blood from the umbilical vein is largely directed from the right atrium across the fossa ovalis and into the left ventricle, where it is pumped into the pulmonary artery and across the ductus arteriosus (DA) into the systemic circulation. The vascular resistance provided by the placenta is lower than the pulmonary capillary bed, which allows for right-to-left blood flow through the ductus arteriosus (DA) and into the descending aorta. However, one potential fetal problem is the normal flow of oxygen rich blood towards the head and neck vessels is disrupted by the inability to pump the oxygenated blood directly into the ascending aorta from the left ventricle (figure 2). (See "Physiologic transition from intrauterine to extrauterine life", section on 'Fetal circulation'.) | |||
==References== | ==References== |
Revision as of 19:25, 10 August 2011
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [2]; Cafer Zorkun, M.D., Ph.D. [3]; Keri Shafer, M.D. [4]; Assistant Editor(s)-In-Chief: Kristin Feeney, B.S. [5]
Overview
Pathophysiology
Dextro-TGA-
- In normal cardiac anatomy, the aorta is positioned posterior and to the right of the main pulmonary artery. Aorta being positioned anterior and slightly rightward of the pulmonary artery. These changes cause the aorta to arise from the right ventricle and the pulmonary artery from the left ventricle (ventriculoarterial discordance).
- In Uncorrected D-TGA the systemic and pulmonary circulations are parallel circuits which means that the deoxygenated systemic venous blood comes to the right ventricle and inplace of going to the lungs, drains back to the systemic circulation via the aorta. Similarly, oxygenated pulmonary venous blood is recirculated to the lungs via the pulmonary artery.
- This parallel circulation is incompatible to life.
- For a child with dextro-TGA to survive, a communication between the two parallel circuits is necessary.
- Various connections that allow mixing in these patients are: patent foramen ovale, ventricular septal defect, atrial septal defect,patent ductus arteriosus or the bronchopulmonary collateral circulation.
- Ventricular septal defect (VSD) occurs (in about 50%) of patients with D-TGA. Patients with a VSD may have other cardiac anomalies like pulmonary stenosis or atresia, overriding of atrioventricular valve, and coarctation of aorta.
- Left ventricular outflow tract obstruction is common in D-TGA and is present in up to 25 percent of patients.
Physiology in-utero
The fetus circulation in-utero is different compared to the extra-uterine circulation. The fetus tolerates the in-utero circulation of D-TGA without much difficulty. Oxygen-rich blood from the umbilical vein is largely directed from the right atrium across the fossa ovalis and into the left ventricle, where it is pumped into the pulmonary artery and across the ductus arteriosus (DA) into the systemic circulation. The vascular resistance provided by the placenta is lower than the pulmonary capillary bed, which allows for right-to-left blood flow through the ductus arteriosus (DA) and into the descending aorta. However, one potential fetal problem is the normal flow of oxygen rich blood towards the head and neck vessels is disrupted by the inability to pump the oxygenated blood directly into the ascending aorta from the left ventricle (figure 2). (See "Physiologic transition from intrauterine to extrauterine life", section on 'Fetal circulation'.)
References
External links
- Diagram at kumc.edu
- Diagram and description at umich.edu
- Royal Children's Hospital, Melbourne
- Mayo Clinic, Arizona - Florida - Minnesota, USA