congenital heart disease
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What is congenital heart disease?
Congenital heart disease (CHD) is a cardiovascular condition caused by genetic and environmental factors that occurs in approximately 8 out of 1,000 live births.
During the complicated evolution of the heart in embryological development, many different types of congenital defects can occur. Some of these defects may not have an effect until early adulthood, while others may cause death at birth. If left untreated, around 40% of infants born with CHD die during their first year.
CHD is classified into cyanotic and noncyanotic varieties. In cyanotic varieties, a shunt bypasses the lungs, sending venous blood into arterial circulation, causing a blue tinge to the infant's skin. Noncyanotic CHD can cause breathing difficulties and failure to thrive.
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How does congenital heart disease affect the heart's structure?
Congenital heart disease arises from the heart's complex development before birth, with structural impacts varying widely based on the specific defect.
Defects in the atrial septum, the wall between the heart's upper chambers, can cause blood to shunt from left to right, increasing pulmonary blood flow and potentially causing right-side heart failure over time. Ventricular septal defects, holes in the wall separating the lower chambers, can also cause blood shunting and, if large, damage the pulmonary circulation.
Other structural issues include aortic coarctation (narrowing of the aorta), valve abnormalities, and underdeveloped heart chambers, such as in hypoplastic left heart syndrome. These defects can lead to a range of complications, from mild problems to life-threatening conditions.
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What are some common types of congenital heart defects?
Congenital heart disease includes a variety of defects that arise as the heart develops in utero. These defects are classified as either cyanotic or noncyanotic. In cyanotic defects, venous blood bypasses the lungs and enters the arterial circulation, causing a blue tinge to the skin.
Common types of congenital heart defects:
* Atrial Septal Defect An atrial septal defect involves a defect in the atrial septum, which permits blood to shunt from the left to the right side of the heart.
* Ventricular Septal Defect A ventricular septal defect is a defect in the partition between the lower heart chambers.
* Pulmonary Valve Stenosis Pulmonary valve stenosis is a narrowing of the pulmonary valve that obstructs blood flow from the right ventricle to the lungs.
* Tetralogy of Fallot This involves a ventricular septal defect, pulmonary stenosis, deviation of the aorta, and right ventricular hypertrophy.
* Hypoplastic Left Heart Syndrome In hypoplastic left heart syndrome, the left-sided heart chambers are underdeveloped.
* Anomalous Pulmonary Venous Return With anomalous pulmonary venous return, the pulmonary veins connect to the right atrium instead of the left.1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How do these heart defects develop before birth?
Congenital heart disease arises from the heart's complex development during embryogenesis. These abnormalities, present at birth, occur in about 8 out of 1,000 live births and can be caused by genetic factors, such as a single mutant gene or chromosomal abnormality like Down syndrome. Environmental factors, such as a mother contracting rubella during the first three months of pregnancy or the use of certain drugs, can also cause congenital heart disease. In most cases, the causes are a combination of genetic and environmental factors.
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What symptoms might a person with congenital heart disease have?
Congenital heart disease, an abnormality of the heart present at birth, can manifest in a variety of symptoms. Infants may exhibit a blue complexion (cyanosis), breathlessness, or feeding difficulties.
Heart murmurs, detected with a stethoscope, are also common. Depending on the specific defect, symptoms may range from mild to life-threatening. In severe cases, infants may fail to thrive. Some defects cause mixing of oxygenated and deoxygenated blood, leading to a bluish skin color. These symptoms result from obstructions in blood flow or abnormal connections within the heart.
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How can doctors find and treat problems caused by congenital heart disease?
Doctors use several methods to detect congenital heart disease. Sometimes, a heart murmur is the first sign. Ultrasonography and amniocentesis can diagnose abnormalities before birth.
Many congenital heart defects can be corrected with surgery, sometimes without a heart-lung machine. For pulmonary stenosis, doctors may use a balloon catheter to enlarge the valve opening. In 1944, physicians developed a procedure for cyanotic abnormalities, which improved the survival rate of infants, and in the early 1950s, they developed surgical procedures for repair.
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congenital heart disease, any abnormality of the heart that is present at birth. Cardiac abnormalities are generally caused by abnormal development of the heart and circulatory system before birth. Abnormal development can be caused by a variety of factors, including infection and use of certain drugs by the mother during pregnancy. Some congenital cardiac abnormalities are inherited and may be transmitted as autosomal or sex-linked traits. However, for some of the more common abnormalities, there is no obvious heritable relationship, nor is the origin of the disease readily explained.
One common type of congenital abnormality is a simple septal defect, where a hole is found in the partition, or septum, between the right atrium and left atrium or between the right ventricle and left ventricle of the heart. The most common such defect is persistence of the foramen ovale, an opening in the atrial septum that is normal before birth and that should close at birth or shortly thereafter. A hole between the two sides of the heart produces an abnormal mixture of oxygenated blood from the pulmonary circulation and deoxygenated blood from the systemic circulation. It also causes a sort of short circuit to develop where more blood flows through the lungs than through the other organs of the body. Ultimately such a condition may cause thickening of the walls of the pulmonary artery as well as pulmonary hypertension (high blood pressure). Increased stress may be placed on the right ventricle as it tries to pump blood through the pulmonary circuits for oxygenation. Right heart failure may then develop, and the supply of appropriately oxygenated blood to the body tissues may become compromised. Defects of the atrium and ventricle can be repaired surgically with ease and great success as long as severe, irreversible pulmonary hypertension has not developed.
Another type of congenital abnormality affects the heart valves, causing valvular insufficiency or obstruction. As with septal defects, valve defects generally can be repaired by surgery. More-complicated defects, however, often involve a combination of abnormalities. An example can be seen in tetralogy of Fallot, a condition where there is narrowing of the valve to the pulmonary artery (pulmonary stenosis), a ventricular septal defect, an aorta that overrides both the right and left ventricle so that it receives blood from both sides of the heart, and severe thickening of the muscle of the right ventricle (right ventricular hypertrophy). As a result of these defects, the circulating blood is deprived of oxygen, causing the bluish discoloration of the skin known as blue baby syndrome.
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Yet another group of congenital heart defects affects the aorta and the pulmonary artery. In the complex abnormality known as transposition of the great arteries, the aorta, the great conduit of blood to the organs and tissues of the body, rises from the right ventricle, which under normal anatomic configurations pumps blood to the lungs; at the same time, the pulmonary artery, the conduit of blood to the lungs, rises from the left ventricle, which normally pumps blood through the aorta to the body. Another condition is patent ductus arteriosus, where a temporary channel that connects the pulmonary artery and the first segment of the descending thoracic aorta during fetal growth fails to close after birth, causing some mixing of oxygenated and deoxygenated blood. In coarctation of the aorta, the aorta may be narrowed just below the point where the arteries supplying the upper part of the body emerge, thus increasing blood pressure in the upper half of the body and reducing pressure in the lower half of the body.
Depending on the constellation of abnormalities, congenital heart disease is often categorized as either cyanotic (causing a bluish skin colour) or noncyanotic. Cyanosis occurs when a mixture of oxygenated and deoxygenated blood courses through the arteries, bringing on the blue-red-violet hue characteristic of deoxygenated blood in the veins.
Some congenital cardiac defects are associated with high neonatal and infant mortality. One example is hypoplastic left heart syndrome, a very serious condition in which the left ventricle and other structures are underdeveloped, severely compromising blood flow through the body. Fortunately, surgical advances have made it possible to correct many defects, so that some patients who once would have succumbed at a very young age now lead longer and relatively normal lives. For some congenital heart disease patients, a heart transplant or combined heart-lung transplant is an option.