SEM_07_01_Blood cells_PARTE2.docx

Some common heart defects There are many types of congenital heart defects ranging from simple to very complex abnormalities. Some of the most common congenital defects are: Ectopia Cordis (Greek: "away / out of place" + Latin: "heart") is a congenital malformation in which the heart is abnormall...

Some common heart defects There are many types of congenital heart defects ranging from simple to very complex abnormalities. Some of the most common congenital defects are: Ectopia Cordis (Greek: "away / out of place" + Latin: "heart") is a congenital malformation in which the heart is abnormally located either partially or totally outside of the thorax. The ectopic heart can be found along a spectrum of anatomical locations, including the neck, chest, or abdomen. In most cases, the heart protrudes outside the chest through a split sternum. - Ectopia Cordis In parallel with the cranio-caudal folding of the embryo, the two endocardial tubes are drawn ventrally so the developing heart becomes situated inside of the thorax. Interferences in the normal descent may result in abnormals positioning of the heart. Inter-Atrial septal defects. Communications between the atria may be the result of a failure in the closure of the foramen ovale (patent foramen ovale) or a true atrial septal defect due to defective development of the foetal septa and the persistence of a common atrium. Although the patent foramen ovale, potentially results in cyanosis (bluish skin colour) and polycythaemia (increased volume of red blood cells), in some individuals, this condition can remain undetected or it is an incidental finding. The occurrence of atrial septal defects usually causes more serious disturbances in the postnatal circulation. Because in postnatal condition blood pressure is higher in the left chambers than in the right ones, blood shunts from the left atrium to the right atrium, causing a volume overload of the right-sided chambers. The magnitude of shunting depends on the size of the defect, the ratio of pulmonary to systemic vascular resistance, and the relative compliance of the two ventricles. Excessive blood flow through the right-side chambers results in their dilation and hypertrophy. - Patent foramen ovale. If the foramen ovale fails to seal after birth, the blood is shunted from the left atrium to the right atrium, because the pressure is highest in the left chambers of the heart. Ventricular septal defects. These anomalies are usually observed in the membranous part of the interventricular septum. They consist in the persistence of some opening in the wall separating the two ventricles. It may occur in isolation but are more often observed with other developmental anomalies. A small defect is of little consequence, but larger openings result in increased pressure on the right ventricle. Patent Ductus Arteriosus. It occurs if the foetal ductus arteriosus fails to close after birth. The ductus arteriosus is a blood vessel that connects the pulmonary trunk to the aortic arch; it allows the blood plump by the right ventricle to bypass the non-functioning foetal lungs. At birth, the lumen of the ductus arteriosus is functionally obliterated and within the next two to three weeks, the closed vessel is transformed into a fibrous band with no lumen that persists as the ligamentum arteriosum. If the ductus arteriosus remains open after birth, blood from the aorta is forced into the pulmonary artery because, in contrast to the foetal circulation, the postnatal aortic pressure normally exceeds pulmonary artery pressure. The result is a continuous murmur and volume overload of the pulmonary vessels and left cardiac chambers. This condition has been described as a hereditary heart defect in some breeds of dogs. - Patent ductus arteriosus Patent ductus arteriosus is a congenital disorder in which the ductus arteriosus does not close after birth. In this condition, blood is shunted from the aorta to the pulmonary artery. Valve defects. Simple congenital heart defects may also involve the heart valves. Some congenital defects include: Stenosis. This defect occurs if the flaps of a valve thicken, stiffen, or fuse together. As a result, the valve cannot fully open. Thus, the heart must work harder to pump blood through the narrow valve. The most common congenital defect is pulmonary valve stenosis. Atresia. This defect occurs if a valve does not form correctly and the valve orifice fails to develop. The valve is completely closed thereby obstructing the outflow of blood. Valve atresia is generally associated with more complex congenital heart abnormalities. Regurgitation. This defect occurs if a valve does not close tightly. As a result, blood leaks back through the valve. - Congenital heart valve abnormalities Congenital heart valve abnormalities, like pulmonary valve stenosis and tricuspid atresia, are birth defects involving one or more of the heart’s four valves. Tetralogy of Fallot. It is the most common complex heart defect in which there is a combination of four defects:1. Narrowing of the right ventricular outflow tract (pulmonary stenosis).2. Enlargement of the aorta that overrides the right ventricle (dextroposition of the aorta).3. Interventricular septal defect.4. Right ventricular hypertrophy. - Tetralogy of Fallot Tetralogy of Fallot comprises:1. A narrowing of the right ventricular outflow tract.2. Aorta dextroposition. 3. Interventricular septal defect.4. Right ventricular hypertrophy