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Cardiac Defects with a Right to Left Shunt (Cyanotic)
In cardiac abnormalities with right-left shunts oxygen-poor blood gets from the right half of the heart into the left side and thus into the systemic circulatory system. In most of the defects with right-left shunts the physiologic shunts present before birth remain functional because no reversal of pressure happens following birth.
- RV outflow obstruction
- RV Hypertrophy
- Overriding AAorta
II. Pulmonary valve atresia
This abnormality is very rare and accounts for only 1-3%. The pulmonary valve is atretic and there is no exit from the right ventricle. Thus, all of the blood flows into the left atrium via the foramen ovale and the lungs only get perfused via a very wide ductus arteriosus.
IIII. Tricuspid atresia
Incidence of 3%. Through atresia of the tricuspidal valve a connection between the right atrium and the right ventricle is missing. Since this abnormality is mostly combined with a VSD, its effects depend on the size of the VSD.
IV. Hypoplastic Left Heart Syndrome
A special case is the Hypoplastic left heart syndrome, a rare (only 2% of all cardiac abnormalities) that includes a poorly developed (hypoplastic) left ventricle that is often only a few millimeters thick. The aortic and mitral valves are constricted (stenotic) or completely closed (atretic). Only the right ventricle supplies both the pulmonary and systemic circulation system with blood. The arterial blood from the left atrium gets into the right atrium and ventricle via the patent foramen ovale (PFO) (L-->R shunt). The ascending aorta is filled retrograde by the blood of the ductus arteriosus (Rß L shunt). This way, the coronaries etc. are supplied with blood flowing retrograde via the PDA, the only way survival is possible for a short time.
Hypoplastic left ventricle
The left ventricle is hypoplastic. Through an open foramen ovale the blood gets to the right side and mixes with the O2 unsaturated venous blood. This left-right shunt via the foramen ovale as well as the right-left shunt via the ductus arteriosus are necessary for survival. Such children are cyanotic.
- Anatomy & Anomalies, Children’s Heart Center, Johns Hopkins University
- Heart Embryology, University of Toronto
- Cardiovascular Embryology, Dept. of Anatomy, Indiana University
- Human Embryoloogy, Organogenesis
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