Illustrations of different types of CHD

Ventricular Septal Defects (VSD): This is a hole (defect) in the wall (septum) between the two pumping chambers (ventricles). These defects are usually noticed early in life. Very small holes make very loud noises (think of poking a small hole in a taught water balloon) because the ventricles pump at high pressure.

The amount of difficulty caused by the VSD is, once again, dependent upon the size of the defect. If there is a lot of blood being forced across a large hole, or many tiny holes, there is more difficulty for the patient.

Once again, blue blood enters the right heart and is pumped out into the lungs as previously explained. The red blood returns to the left heart from the lungs, but as it comes into the high-pressured LV, some of the blood meant to be pumped out to the body is forced across the VSD into the RV. There the extra blood is pumped out to the lungs. Over time, the lungs see more blood volume than they should, and the body sees less oxygen rich blood than it should.

These sorts of defects are generally closed by surgery if they are big enough to cause problems. Tiny holes are often left untouched, as they are not harmful. Some institutions are closing select VSD s in the cardiac catheterization lab.













In a normal heart, oxygen-poor (blue) blood returns from the body to the right atrium, and is pumped by the right ventricle through the pulmonary artery into the lungs. In the lungs the blood receives oxygen (and gives up carbon dioxide), then returns to the left atrium on the left side of the heart. The left ventricle pumps the oxygen-rich blood through the aorta out to the body.

But in truncus arteriosus, oxygen-poor (blue) and oxygen-rich (red) blood mixes in the common truncal vessel. Some of the mixed blood flows through the branch that becomes the pulmonary artery and on to the lungs, and some of it goes into the aortic branch and continue to the body.

The mixed blood that goes to the body doesn’t have as much oxygen as the body needs, and causes varying degrees of cyanosis (blue color of the skin, lips and nailbeds).

Open heart surgery to separate the pulmonary artery and the aorta is needed, and is usually performed in the first few weeks of the baby’s life.

  • Babies with truncus arteriosus also have a ventricular septal defect (VSD), an opening in the wall of tissue (ventricular septum) that normally separates the right and left ventricles. The VSD is closed at the time of surgical correction of the truncus arteriosus.
  • Often, the valve of the single vessel is defective in form and function, with abnormal leaflets that allow leakage (regurgitation) and/or obstruction of blood flow.


  • Truncus arteriosus can be associated with chromosomal disorders such as velo-cardio-facial syndrome (also known as 22q11 deletion syndrome or DiGeorge syndrome).

(D-) Transposition of the Great Vessels: This occurs when the great vessels (aorta and pulmonary artery) are reversed. Some cardiologists say that the circulation is “in parallel” rather than “in series”. This means that the blue blood, which is pumped through the right side of the heart, bypasses the lungs, going directly out the aorta. The red blood comes directly from the lungs into the left side of the heart, where it gets pumped back to the lungs.

This defect is not compatible with life, unless there is a hole somewhere within the heart, or if the ductus stays open. These “defects” allow the two circulations to “mix” until the heart defect can be definitively fixed by surgery.

Aorta (AO)
Pulmonary Artery (PA)
Right Atrium (RA)
Left Atrium (LA)
Right Ventricle (RV)
Left Ventricle (LV)

Tetralogy of Fallot (ToF): “Tetra” means “four”; therefore, there are four defects that make up this form of heart disease. Due to abnormal closure of the ventricular septum in the fetus, the patient is left with a ventricle septal defect (VSD), an over-riding aorta (where the aorta lives over the ventricular septum), pulmonary stenosis (PS), and a thick, muscle-bound right ventricle due to all the work created pumping against the tight pulmonic valve (PV).

Blue blood returns to the right heart as usual, but has some difficulty getting out to the pulmonary arteries, depending on the tightness or narrowness of the pulmonary valve, and the area underneath the pulmonary valve. The degree to which the patient appears blue depends upon how much blood can get out to the lungs to pick up oxygen. Some of the blue blood can get pushed across the VSD into the left ventricle (LV) and circulated out to the rest of the body.

The red or oxygen-rich blood returns to the left atrium (LA), goes to the LV and is pumped out to the aorta. If the PS is not too severe, some of the red blood can be pushed across the VSD and pumped back into the PA s.

Patients with ToF may never look blue, however some patients can have “tet” spells or hypercyanotic spells. These seem to occur in patients with the thickest, most muscular, narrowest right hearts. The muscle clamps down beneath the pulmonary valve and blood cannot get out into the lungs. The patient appears dark blue, gray, or pale and is often very distressed or (worse) unresponsive. This is an emergency, and parents may push the patients knees to the chest and keep the patient quiet until emergency helps arrives.

Pulmonic Stenosis (PS): This is an abnormality of the pulmonary valve (PV), which is the heart valve that opens up into the pulmonary or lung arteries. If the valve is thick, and does not open properly (and therefore, does not get out of the way of blood flowing into the pulmonary artery, not enough of the blue blood can get out in the lungs to pick up oxygen and return to the heart properly. In its mildest form, PS creates a murmur, which is the sound of turbulent blood flowing out of the right ventricle into the pulmonary arteries (PAs). In its most severe form, blood cannot leave the right ventricle to pick up oxygen, and the valve needs to be fixed immediately in the catheterization lab or the operating room.

Patent Ductus Arteriosus (PDA): The PDA is a normal structure in the fetus, in premature infants and in newborn babies. It usually closes all by itself in the first 2 days of life.

See the diagram, and note that the PDA is a blood vessel, which connects the pulmonary arteries (PAs) to the aorta (AO). In the normal heart, the pressure in the AO is higher than it is in the PA, which means that every time blood is pumped into the AO, some of the blood which, should be circulated to the body (red blood) gets pumped into the PA (blue blood). This extra blood to the lungs can cause problems in premature infants, making it necessary to close the PDA with medicine or by surgery. Overtime, the PDA can cause harm in larger infants and children, although many people have gone through life with small, silent PDAs. PDAs can be closed by cardiac catheterization or by surgery in older babies and children.

In some heart defects, it is necessary for the PDA remain open. In these cases, doctors will give babies a medication known as prostaglandins (PGE1) through an intravenous line (IV).

Hypoplastic Left Heart Syndrome: “Hypoplasia” is a term, which means something is made small. Therefore, in this defects the left ventricle fails to develop normally. As the left ventricle (LV) is the “workhorse” of the heart, patients with this syndrome are not able to live to long without surgical attention. Once again, the severity of the defect depends in how small the left ventricle, mitral valve and aorta (AO) are, how much flow goes through the left heart, and how big the holes are within the heart.

Aorta (AO)
Patent Ductus Arteriosus (PDA)
Right Atrium (RA)
Left Atrium (LA)
Right Atrium (RA)
Right Ventricle (RV)
Left Ventricle (LV)


AO: Aorta
PA: Pulmonary Artery


Please note: Only an enlarged view of the aorta and pulmonary artery are shown in this drawing. The rest of the heart is not shown.

Frequently, the aortic valve is also abnormal when the diagnosis of coarctation is made. However, this particular lesion will not be discussed at present.


There are various forms of coarctation, which is narrowing of either a long or a short segment anywhere along the aorta. It may occur anywhere within the chest or abdomen, although it most commonly occurs in the fashion shown in the diagram. Once again, when a coarctation is diagnosed in a given patient depends on the degree of narrowing and where the coarctation is located along the aorta.


Coarctation is an “obstructive lesion”, as it prohibits flow to the areas beyond the area of narrowing. Because flow cannot get beyond the area of narrowing, the blood pressure builds up in the area before the narrowing. The flow and pressure beyond the narrowing is decreased, meaning that the areas that are served by the lower aorta, such as the kidneys, may not be receiving the appropriate amount of blood.  Coarctation may be repaired in the cardiac catheterization lab, or by surgery.

Atrioventricular canal defect

Right atrium (RA)
Atrial Septal Defect (ASD)
Pulmonary artery (PA)
Aorta (AO)
Left atrium (LA)
Right ventricle (RV)
Ventricular Septal Defect (VSD)
Left ventricle (LV)




A Normal Heart Illustration








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