Pulmonary Atresia
This defect is a form of Tetralogy of Fallot in which there is complete obstruction of the Pulmonary Artery resulting in total diversion of blood from the right ventricle into the aorta. Survival depends on the ductus remaining open in the early days of life (in order for blood to reach the lungs), or on the presence of other connecting blood vessels between the Aorta and the Pulmonary Arteries in the lungs (Collaterals). Most babies will need a 'Shunt' operation during infancy, involving insertion of a tiny piece of artificial tube (made from Goretex) between the Aorta, or a branch (usually one of the arm arteries), and one of the branch Pulmonary Arteries. Complete Repair is carried out at two to three years. Complete repair for Pulmonary Atresia is usually carried out after the first year of life, though sometimes it may be performed earlier.
Partial Situs Inversus
I could not find any pictures of this anomaly. Essentially, situs inversus is the transposition of the internal organs. The heart is on the right side of the body (instead of the left like the rest of us), the liver, stomach, etc. are also reversed. McKenna's condition is partial because, as noted in the diagram below, only half of her heart inverted. The left atrium is over the right ventricle and the RA is over the LV.
Transposition of the Great Vessels (TGV)
In this congenital heart defect, the aorta (the main artery that carries blood to the body) originates from the right ventricle and the pulmonary artery (the artery that carries low oxygen blood to the lungs) from the left ventricle, resulting in two separate circulation?s.
Because the great arteries are reversed, the aorta carries blood from the right ventricle. This low oxygen rich blood and likewise the pulmonary artery carries blood from the left ventricle. This is already oxygen rich blood that is being carried back to the lungs. In order for the infant born with transposition of the great arteries to survive, they must have some communication between the right and the left sides of the heart to allow oxygen rich blood to reach the body. This mixing of blood is possible through any of the following: ASD, VSD, PDA. Even though there is mixing of oxygenated and de-oxygenated blood, it is often not adequate to sustain life for an extended period of time. Babies with transposition are extremely blue at birth.
The most common surgical procedure to correct this defect is called an arterial switch operation. That is, the major arteries are "switched". The aorta is connected to the left ventricle. This allows oxygen rich blood to be pumped to the body. The pulmonary artery is connected to the right ventricle. This allows low oxygen blood to go to the lungs where it can be oxygenated. Other surgical defects may also be needed to correct the communication between the left and right sides of the heart that was once needed for survival.
McKenna's heart depicted by Dr. Singh
The following are the abbreviations used in the diagram: AO - aortaRPA/LPA - right/left pulmonary arteryPDA - Patent ductus arteriosusPV - pulmonary veinSVC/IVC - superior/inferior vena cavaRA/LA - right/left atriumRV/LA - right/left ventricleASD - atrial septal defectVSD - ventrical septal defect
It is somewhat ironic that with all of the problems that McKenna has, she probably would not have survived if any one of them did not exist (although things would be great if none of them did :-).
As you can see the blood coming back from the body/lungs goes to the correct atria. The atria then feed the wrong ventricles - which is fine because the aorta and pulmonary artery are attached to the wrong ventricles. This does create a problem, however, because the right ventricle is smaller that the left and is meant to push blood the small distance to the lungs and not throughout the body. This will probably need correction before (or during) McKenna's final surgery.
The next problem is the lack of a pulmonary valve. This does not allow blood to flow from the heart to the lungs. To correct this, the PDA (or some other collateral means) allows blood to flow from the heart to the pulmonary arteries. Because all blood flows out of the heart through the aorta (and because the PDA allows such a small amount of blood to the pulmonary arteries, the aorta is much larger than normal and the pulmonary arteries are much smaller.
Anyway, the blood that flows back from the body would not be able to get to the lungs, or return to the body, if the ASD/VSD were not present. Because they are, the blood from the body is able to cross over to the opposite atrium/ventricle and mix with the oxygenated (red) blood from the lungs and flow back to the body.
Yes, I realize that all of this is a repeat of what is discussed for each of the problems McKenna's heart has. However, the problems listed above identify (relatively) easy fixes. Because of the number of issues in McKenna's heart, the fix will definitely not be an easy one. The cardiologists are not even sure yet what they are going to do to eventually repair the defects. The first step, though, will be to find a reliable means of getting blood to the lungs - the central shunt.
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