Atrial Septal Defect
In a heart with an Atrial Septal Defect (ASD) there is communication between the right and left atria which causes a left to right shunting of blood due to the lower pressure in the pulmonary circulatory system. Consequently there is a mixing of oxygenated (systemic) and deoxygenated(pulmonary) blood.
There are two types of ASD:
• Primum type involves the endocardial cushions.
• Secundum type involves septum primum or septum secundum.
Persistent Atrioventricular Canal
The persistent atrioventricular canal results from the failure of the superior and inferior cushions to fuse. Thus there is a single atrioventricular canal in which all four chambers may freely communicate. Because the cushions do not fuse the atrial and ventricular septa cannot fully form as they rely on the cushions to form the membranous portions of these septa.
Ventricular Septal Defect (VSD)
The ventricular septal defect is the most common of all congenital heart anomalies. It may be caused by any of the four malformations:
• Deficient development of the proximal conus swellings.
• Failure of the muscular portion of the interventricular septum to fuse with the free edge of the conus septum. (Membranous VSD)
• Failure of the endocardial cushions to fuse.
• Excessive diverticulation of the muscular septum-perforations in the muscular interventricular septum. (Muscular VSD)
In the case of a VSD there is a massive left to right shunting of blood and pulmonary hypertension is also observe. The absence of the interventricular septum results in a Common Ventricle.
Transposition of the Great Vessels
Transposition is a condition in which the aorta arises from the right ventricle and the pulmonary trunk from the left. This anomally is due to the failure of the truncoconal swellings to grow in the normal spiral direction. There is also a ventricular septal defect and a patent ductus arteriosus.However, these secondary defects make life possible as they provide a way for oxygenated blood
to reach the entire body.
Persistant Truncus Arteriosus
A persistent truncus arteriosus results when the truncoconal swellings fail to grow. The single artery, the truncus arteriosus, arises from both ventricles above the ventricular septal defect,allowing pulmonary and systemic blood to mix. Distally, the single artery is divided into the aorta and pulmonary trunk by an incomplete septum.
Tetralogy of Fallot
This condition results from a single error i.e. the conus septum develops too far anteriorly giving rise to two unequally proportioned vessels — a large aorta and a smaller stenotic pulmonary trunk. The four main characteristics of Tetralogy of Fallot are:
• pulmonary stenosis
• ventricular septal defect (VSD) of the membranous portion (the septum is displaced too far anteriorly to contribute to the septum)
• overriding aorta (the aorta straddles the VSD)
• right ventricular hypertrophy due to the shunting of blood from left to right. (The pressure in the right ventricle is increased causing the walls of the right ventricle to expand.)
Dextrocardia
Dextrocardia is an anomaly in which the primitive heart tube folds to the left in a mirror image of a normal bulboventricular loop. This usually occurs when all the organ systems are reversed, a condition called situs inversus.
In a heart with an Atrial Septal Defect (ASD) there is communication between the right and left atria which causes a left to right shunting of blood due to the lower pressure in the pulmonary circulatory system. Consequently there is a mixing of oxygenated (systemic) and deoxygenated(pulmonary) blood.
There are two types of ASD:
• Primum type involves the endocardial cushions.
• Secundum type involves septum primum or septum secundum.
Persistent Atrioventricular Canal
The persistent atrioventricular canal results from the failure of the superior and inferior cushions to fuse. Thus there is a single atrioventricular canal in which all four chambers may freely communicate. Because the cushions do not fuse the atrial and ventricular septa cannot fully form as they rely on the cushions to form the membranous portions of these septa.
Ventricular Septal Defect (VSD)
The ventricular septal defect is the most common of all congenital heart anomalies. It may be caused by any of the four malformations:
• Deficient development of the proximal conus swellings.
• Failure of the muscular portion of the interventricular septum to fuse with the free edge of the conus septum. (Membranous VSD)
• Failure of the endocardial cushions to fuse.
• Excessive diverticulation of the muscular septum-perforations in the muscular interventricular septum. (Muscular VSD)
In the case of a VSD there is a massive left to right shunting of blood and pulmonary hypertension is also observe. The absence of the interventricular septum results in a Common Ventricle.
Transposition of the Great Vessels
Transposition is a condition in which the aorta arises from the right ventricle and the pulmonary trunk from the left. This anomally is due to the failure of the truncoconal swellings to grow in the normal spiral direction. There is also a ventricular septal defect and a patent ductus arteriosus.However, these secondary defects make life possible as they provide a way for oxygenated blood
to reach the entire body.
Persistant Truncus Arteriosus
A persistent truncus arteriosus results when the truncoconal swellings fail to grow. The single artery, the truncus arteriosus, arises from both ventricles above the ventricular septal defect,allowing pulmonary and systemic blood to mix. Distally, the single artery is divided into the aorta and pulmonary trunk by an incomplete septum.
Tetralogy of Fallot
This condition results from a single error i.e. the conus septum develops too far anteriorly giving rise to two unequally proportioned vessels — a large aorta and a smaller stenotic pulmonary trunk. The four main characteristics of Tetralogy of Fallot are:
• pulmonary stenosis
• ventricular septal defect (VSD) of the membranous portion (the septum is displaced too far anteriorly to contribute to the septum)
• overriding aorta (the aorta straddles the VSD)
• right ventricular hypertrophy due to the shunting of blood from left to right. (The pressure in the right ventricle is increased causing the walls of the right ventricle to expand.)
Dextrocardia
Dextrocardia is an anomaly in which the primitive heart tube folds to the left in a mirror image of a normal bulboventricular loop. This usually occurs when all the organ systems are reversed, a condition called situs inversus.
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