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Tetralogy of Fallot Video Series
This video series explains Tetralogy of Fallot (TOF), a congenital heart malformation in which blood flow is blocked from entering the lungs. Fetal Heart Program and Cardiac Center staff discuss how they diagnosis the condition before birth, monitor babies through pregnancy and delivery, and surgically repair the defect.
Videos in this Series
Transcript: What is Tetralogy of Fallot (TOF)?
Thomas Spray, MD: All of heart surgery is 50 years old, and we've come from a situation of being able to treat nothing to being able to at least deal with most, if not the vast majority, of congenital heart defects in a way that allows children to grow into adulthood.
Jack Rychik, MD: We live in an era where there are very few things that we really can't take care of.
Thomas Spray, MD: Tetralogy of Fallot was one of the first significant congenital heart defects to be addressed surgically.
Gil Wernovsky, MD: It has been surgically managed since the 1940s, so there's actually some 40- and 50-year-old patients.
Thomas Spray, MD: So there are many people out there with Tetralogy of Fallot who are in their 30s, 40s, 50s, had children of their own who are doing fine, who have had repairs of that particular heart defect.
Jack Rychik, MD: Tetralogy of Fallot is a form of congenital heart disease initially described by Etienne Fallot, who was a French pathologist in mid-1800s. He identified four specific, associated features with this particular form of congenital heart disease.
J. William Gaynor, MD: The most important features are that there's a ventricular septal defect, or a hole between the two pumping chambers of the heart and blockage of blood flow getting out to the lungs. In some children there's almost no blockage, and they can actually have too much blood flow to the lungs. In other children the blockage can be so severe that there's not enough blood flow, and they're very sick after birth. And sometimes there's a complete blockage, or what's caused pulmonary atresia.
Jack Rychik, MD: In order to understand and comprehend any of the different forms of heart disease that exist, it's very important to make sure we understand what the healthy or the normal heart looks like. The normal heart has two sides--a right side and a left side and four chambers--the top receiving chambers or atria and the lower chambers, which are thick-walled pumping chambers, called ventricles. The red blood cell will come from either the superior vena cava or the inferior vena cava and enter into the right atrium. The blood then flows across the tricuspid valve to the right ventricle. The right ventricle then squeezes and ejects that blood cell into a vessel called the pulmonary artery. The pulmonary artery splits into two vessels, each going to the lungs. As that red blood cell makes its way through the lung, it returns through the pulmonary veins to the left atrium. That blood is now oxygenated. It's picked up oxygen then goes across the mitral valve into the left ventricle, which does most of the work, in terms of delivery of blood flow to the body. That blood cell is now ejected into the aorta to some organ or muscle or skin in the human body. Now, there are some significant differences between the heart in the newborn and the heart in the fetus.
Elizabeth Goldmuntz, MD: The heart actually is-- assumes its almost complete anatomy often before a woman would even know she was pregnant.
J. William Gaynor, MD: The heart is actually functioning and pumping blood to the baby throughout most of fetal life.
Jack Rychik, MD: Because the lungs are collapsed in the fetus and it's really the placenta through which much of the oxygenation takes place through the mother, there are various bypass pathways within the fetal heart that direct blood away from the lung. The first is a structure called the foramen ovale. That's a communication between the two top chambers of the heart that allows for blood to go from the right atrium to the left atrium. In fact, because there is very little blood that's returning from the lung, which would normally go to the left side, the majority of blood that fills the left atrium and left ventricle is coming across the foramen ovale from the right side. Because the lungs are collapsed, there's high pressure, high resistance in the lungs as blood is ejected out the right ventricle and enters into the main pulmonary artery. Very little goes down into the lungs themselves. The majority goes into a structure called the ductus arteriosus, which is the second point in communication between the pulmonary artery and the descending aorta. The third structure that's important that connects the umbilical vein to the fetal circulation is a site, a junction, called the ductus venosus. That acts as somewhat of a resistor, if you will, in terms of controlling the return of blood from the placenta to the fetal circulation. Birth is a wonderful process and an amazing process, and there's a dramatic change that takes place in what we call the fetal transition. This transition of the circulation from a fetal life to neonatal life. As soon as the cord is clamped, the ductus venosus ceases to carry blood to the heart, and it begins to constrict within the first few hours or days of life. The very first thing that happens when the fetus is born is it takes its first breath, the lungs expand, and so the resistance or pressure in the lungs drop and that promotes blood flow into the lung itself. The ductus arteriosus begins to constrict and is typically fully closed within 24 to 48 hours of life, and blood is now then fully directed into the lung. As the blood returns to the left side of the heart after traversing the pulmonary circulation and picking up oxygen, pressure in the left atrium rises just a bit and the trapdoor of the foramen ovale, which was open before birth, now begins to close, usually within the first few days of life.
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