CYANOTIC CONGENITAL HEART DEFECTS

Congenital heart defects is also referred to as CHD.  The heart is improperly formed as a result of abnormal development of the cardiac structures during early embryonic life.  These issues occur very early in pregnancy, often times before the women are even aware of being pregnant.

The cause for congenital heart defects is unknown, but is believed to arise from multiple, interacting environmental and genetic factors, such as:

• Maternal diabetes, poor glucose control very early in pregnancy raise risk
• Family history of CHD
• Fetal exposure to rubella virus in the first trimester
• Exposure to substances- fetal exposure to street drugs, alcohol, environmental toxins, meds
• Chromosomal defects (Down Syndrome Edward’s Syndrome, Marfan Syndrome)

Acyanotic Congenital Heart Defects

Acyanotic Defects include the defects that allow the normal flow of blood through the heart:

• Aortic Stenosis (AS) aortic valve between aorta and left ventricles is narrowed. Creates reduced blood flow out to the body and increased pressures in the lungs, left atrium, left ventricle, possibly resulting in heart failure and pulmonary edema.
• Pulmonary stenosis (PS) pulmonary valve, between pulmonary artery and right ventricle, is narrowed. Blood flow to the lungs is reduced, and workload of the right ventricle is increased, possibly resulting in heart failure.
• Coarction of the aorta- a section of the aorta is narrowed, sometimes resulting in reduced blood flow to the lower body and increased blood pressure in the oppeer body. The heart must work harder, and may be so much that the heart fails.

Shunting Congenital Heart Defects

Shunting defects include defects that permit abnormal communication between cardiac structures, such as an opening in the septum between heart chambers. Generally blood is forced into the right side of the heart from the left because the left side pressure is generally higher. This causes a circulatory overload of the lungs, resulting in pulmonary edema and heart failure.
Shunting defects include:

• Atrial septal defect (ASD), an opening in the septum between the 2 atria
• Ventricular spetal defect (VSD), opening in septum between 2 ventricles, most common type of CHD.
• Atrioventricular canal or AV septal defect (AVSD) an abnormal opening where all four chambers come together in the center of the heart, often as an extension of ASD and/or VSD.
• Patent ductus arteriosus (PDA)- ductus arteriosus vessel, a fetal circulatory structure connecting the pulmonary artery and aorta, fails to close spontaneously within several days following birth. Blood then flows through this vessel from aorta to pulmonary artery and into lungs possibly causing pulmonary edema and heart failure.

Cyanotic Congenital Heart Defects

Cyanotic defects cause deoxygenated blood to flow out into the body, rather than to the lungs. This produces pronounced cyanosis, and affected neonates were often referred to as “blue babies.” These associated defects are lifesaving, as they permit the addition of oxygenated blood to the de-oxygenated blood in the left ventricle and aorta until surgical correction occurs.

• Transposition of the great arteries (TGA)—the aorta and pulmonary artery are reversed in position, with the aorta arising from the right ventricle and the pulmonary artery arising from the left ventricle.  This results in two completely separate circuits, the pulmonary circulation and the systemic circulation. In the systemic circulation, deoxygenated blood from the right ventricle enters the aorta, circulates through the body, and returns to the right atrium without being routed to the lungs. In the pulmonary circulation, oxygenated blood from the left ventricle enters the pulmonary artery, travels to the lungs, and then back again to the left atrium without circulating through the body. Clearly, this condition would be incompatible with life unless another defect, such as ASD, was present to allow the addition of oxygenated blood to the systemic circulation. Surgical correction is indicated to move the vessels to their normal locations.
• Hypoplastic left heart syndrome- the left side of the heart is underdeveloped and unable to pump blood out to the body. PDA is essential to life for these neonates, as this allows blood to flow into the aorta to the body. Prostaglandin is used to keep the PDA from closing until treatment occurs, which involves a 3-stage surgery or a heart transplant.

NORMAL CIRCULATION
A major event in the life of every neonate is the dramatic switch from fetal circulation to air-breathing circulation at the moment of birth. Because the lungs do not function inutero, fetal circulation is designed to shunt blood away from the solid lung tissue, instead receiving oxygen and nutrients from the placental blood supply. At the moment of birth, however, when the newborn takes his or her first breath and the lungs inflate, pulmonary vascular pressure decreases, allowing blood flow into the lungs. This permits the establishment of normal, adult-type circulation. From the lungs, oxygenated blood travels through the pulmonary veins to the left atrium, then to the left ventricle, and out to the body through the aorta. After circulating through the body, deoxygenated blood flows into the right atrium, to the right ventricle, and through the pulmonary arteries to the lungs, where oxygen is picked up and waste products removed. Any deviation in the function or structure of these processes can create significant problems in perfusion and oxygenation.