Eight out of every 1,000 infants is born with a congenital cardiac disease, according to Henry Sondheimer, M.D., professor emeritus at the University of Colorado Denver School of Medicine. One way to classify these diseases is by whether or not the infant is cyanotic. If cyanotic, the infant has a purple or dark blue color to the skin and lips, because not enough oxygen is being distributed. The complex congenital cardiac diseases include tetralogy of Fallot, transposition of the great arteries and tricuspid atresia, all cyanotic diseases.
Cardiac Circulation
The human heart has four chambers; the two upper ones are referred to as atria, while the two lower chambers are the ventricles. Blood normally enters the right atrium, and then passes to the right ventricle. The blood exits the ventricle through the pulmonary artery, so it can get to the lungs to pick up oxygen. The oxygenated blood will go into your left atrium, then your left ventricle, to leave your heart through the aorta. The blood will then circulate through your body, dropping off oxygen, and returning to your right atrium, to start the process again.
Tetralogy of Fallot
Sondheimer writes in "Current Diagnosis & Treatment: Pediatrics," published in 2009, that this is the most common cyanotic, congenital cardiac disease. Infants with this disorder has four problems. First of all, the pulmonary artery is too narrow, which interferes with the free passage of blood to the lungs. But the heart is a muscle, so the right ventricle gets thicker trying to get the blood through the narrowed pulmonary artery. The thickened right ventricle is the second problem. The third problem is that the infant has what is called a ventricular septal defect. In this defect, there is an abnormal opening between the left and right ventricles. Because the right ventricle is abnormally thick, blood with no oxygen passes from the right ventricle to the left ventricle, then out the aorta to circulate throughout the body. And the last problem the infant has is an aorta that covers both ventricles. So again, some deoxygenated blood from the right ventricle will go into the aorta and circulate.
Transposition of the Great Arteries
In this congenital cardiac disease, instead of the pulmonary artery being connected to the right ventricle and the aorta (an artery) being connected to the left ventricle, their positions are switched. So, instead of blood leaving the right ventricle to pass through the pulmonary artery to the lungs, it passes through the aorta and circulates throughout the body. But because this blood did not go to the lungs yet, it is all deoxygenated blood. Thus, no oxygen is being delivered to any tissues or organs. Sondheimer says this disorder is the second most frequent cyanotic, congenital cardiac disease. Infants who are born with this condition are critically ill and cyanotic.
Tricuspid Atresia
As explained by Sondheimer, when blood passes from the right atrium to the right ventricle, it passes through a valve called the tricuspid valve. In tricuspid atresia, the valve is not there. If the infant also has an atrial septal defect, an abnormal opening between the right and left atria, this will allow blood to flow to the left atrium. But, it will be deoxygenated blood. If the infant as a ventricular septal defect, the pressure in the left ventricle will be higher than that in the right, so blood can flow from the left ventricle to the right ventricle, and then to the lungs. In any case, most infants will be cyanotic at birth.
References
- "Current Diagnosis & Treatment: Pediatrics"; William Hay, Jr., M.D., Myron Levin, M.D., Judith Sondheimer, M.D., Robin Deterding, M.D.; 2009
- "Handbook of Pathophysiology"; Elizabeth Corwin, MSN, PhD, FNP; 2000
