Anatomy And Physiology

Anatomy Physiology



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Approximately one out of every 125 infants born, will be born with some degree of structural problem with their heart. There are many types of heart defects found in children. Some of them are far more common than others. In addition, the severity of the different congenital heart defects can vary from child to child.

The heart begins development in a fetus at a very young age. Within a the first couple of months after conception, the heart becomes developed to the point where it is capable of beating. When it first begins forming in the fetus, the heart is a straight tube. This tube then twists and turns itself into the structure that we know as the heart. Sometimes these twists and turns do not form properly. This leads to heart defects in children.

Tetralogy of Fallot

The first heart defect seen in children is called the Tetralogy of Fallot, or TOF. This congenital heart defect accounts for up to 7% of all cases of heart defects in children.

TOF involves four distinct problems with the heart. First, the pulmonary valve leading from the heart to the lungs will become dysfunctional. Secondly, the aorta, which is the major vessel leading from the heart to the rest of the body, does not develop properly. Third, the right ventricle, which is the chamber responsible for pumping blood to the lungs, becomes too large. And lastly, there is an inappropriate hole connecting the chambers of the heart known as the ventricles.

The malformations seen in TOF have a small spectrum of severity. The degree of obstruction caused by the defective pulmonary valve is the primary determinant in the severity of the symptoms related to TOF. Some children will present symptoms within hours of being born, while others will not have problems until later in life.

The most common symptoms associated with TOF include lack of oxygen to the tissues of the body, which presents as a condition known as cyanosis. Cyanosis makes a person take on a slightly bluish tinge. In addition rapid breathing is a commonly seen symptom of TOF.

Hypoplastic Left Heart

Hypoplastic left heart syndrome is a serious condition which is a leading cause of death due to heart defects in children. This condition involves a lack of development in the chambers of the heart which pump blood throughout the body. The left ventricle, aortic valve, mitral valve, and the first part of the aorta are underdeveloped to the point of being nonfunctional. This condition prevents blood from being pumped from the heart to the rest of the body.

An infant born with hypoplastic left heart syndrome, will rapidly go in to heart failure after birth. There are surgical corrections available, however they are quite complicated and the success rate is not particularly high.

Patent Ductus Arteriosus

A patent ductus arteriosus is a remnant of fetal circulation which is supposed to change after birth. This is a reasonably common cause of heart defects in children, accounting for up to 10% of all cases of congenital heart disease.

Before birth, there is a small connection between the aorta and the pulmonary artery known as the ductus arteriosus. In a fetus this connection allows proper mixing of the blood, which is necessary as the fetus does not receive oxygen from its lungs. After birth this connection closes via a complex system of hormonal signals. In some cases, this connection does not close, leading to a patent ductus arteriosus.

The symptoms of a patent ductus arteriosus relate to the size of the defect and which way the blood is inappropriately flowing. An infant with a patent ductus arteriosus can go into heart failure, or have difficulty breathing. When listening to the chest of a child with a patent ductus arteriosus, a very distinctive murmur can be heard. There are corrections for a patent ductus arteriosus, first involving the use of medication. If this does not work there are surgical options to correct the abnormality.

Transposition

Transposition of the great arteries is a condition where the two primary arteries leading out of the heart are reversed. In normal people, the aorta comes out of the left side of the heart and supplies blood to your body. The pulmonary artery comes out of the right side of the heart and supplies blood to your lungs. With a transposition these arteries are reversed. This condition is normally fatal, as oxygenated blood is not able to get to the rest of your body. In some cases, infants are able to survive for a short time if there is also a small hole in the heart, which allows blood to mix. If the infant is able to survive for a short time, surgery can be done to correct this abnormality.

Coarctation of the Aorta

Coarctation of the aorta is a narrowing of the primary artery leading out of the heart. The aorta is a large artery which is responsible for supplying blood to virtually the entire body. Coarctation is a narrowing of the aorta. Coarctation can vary in severity, and can be corrected with surgery. There is an association with coarctation of the aorta and Turner's syndrome. Turner's syndrome is a genetic abnormality seen in girls.

Ventricular Septal Defect

Ventricular septal defects occur when there is a small hole in the wall between the two lower chambers of the heart. The lower chambers of the heart are known as the ventricles, and they are typically separated by a wall known as a septum. From time to time, this septum will not develop properly, leaving a small hole that blood can flow through in appropriately.

Most ventricular septal defects will close without medical intervention. By age 10, over 75% of infants born with a ventricular septal defect will have complete resolution of the problem. The severity of the ventricular septal defect is related to how large the hole is. In some cases it may be necessary to perform surgery to close the hole. Ventricular septal defects are by far the most common cause of heart defects in children, accounting for up to 25% of all cases.

Atrial Septal Defect

Atrial septal defects are similar to a ventricular septal defect, however they are seen in the upper chambers of the heart. The two upper chambers of the heart are known as the atria. It is possible for their to be an inappropriate hole in the atria, just like there could be one in the ventricles. Atrial septal defects account for up to 8% of heart defects seen in children, and are far more common in girls.

There are several subtypes of atrial septal defects, and again the degree of severity is related to the size of the hole. Most cases of atrial septal defects will result on their own, or with minimal intervention.

Heart defects in children can be a serious medical issue. This information is meant to be a brief overview of some of the more common heart defects seen in children. It is by no means meant to be complete or comprehensive. If you have any questions about heart defects in children, talk to your doctor.

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