Tuesday, February 5, 2013

Transposition of the Great Arteries (TGA)

Transposition of the Great Arteries (TGA)

In Transpotition of the Great Arteries both, Aorta and Pulmonary Artery are transposed (inverted) and arise from the oposit ventricles. This is a cyanotic congenital heart defect (condition existing at birth) usually detected within the first hours or days from birth.

When TGA is present, there is a deficit of highly oxygenated blood in the body, since deoxygenated (poor in oxygen, blue) blood is being pumped from the Right Ventricle (RV) back to the body through Aorta, which raises from the RV instead of the Left Ventricle (LV).

On the other hand, the rich in oxygen blood (oxygenated, red) coming from the lungs to the LV is pumped back to the lungs through Pulmonary Artery which raises from the the LV instead of the RV.

The baby is not affected by the TGA before birth and may no be affected for some time after birth due to 2 natural conditions.

First is an opening between the atria, the two upper chambers of the heart. This hole is called PFO, Patent Foramen Ovale.

The second is a blood vessel between the Pulmonary Artery and the Aorta, called PDA, Patent Ductus Arteriosus. Both of them allow mixing of the oxygenated and deoxygenated blood while in utero and usually close on their own soon after birth.

One they close, the poor in oxygen blood will be flowing back to the body.
This can be postponed for some time by performing a Rashkind Balloon Septostomy. A catheter with a tiny balloon is inserted to baby's heart through the big vein in baby's groin, led through the PFO, inflated and pulled back through the PFO to enlarge it allowing more blood to mix. The baby will still be blue, but less blue than prior the procedure.

A surgical intervention will eventually be required. The most common procedure is Arterial Switch also called Jatene operation (after Brazilian surgeon Adib Jaten who as first successfully performed dr. Mustard's arterial switch procedure.

During the Arterial Switch the Aorta is cut above coronary arteries and Pulmonary Artery is cut at the same level. Then they are literally switched and sewn respectively the Aorta to the base of Pulmonary Artery and Pulmonary Artery to the base of Aorta allowing for the proper blood flow.

The whole between the atria created during the Rashkind Ballon Septostomy is also closed during this operation by a Gore-Tex patch sawed over it.

About 30%-40% of children with TGA also have VSD and Sub pulmonary Stenosis They both are corrected during the Arterial Switch.

In case severe Pulmonary Stenosis the Rastelli's procedure is performed. A conduit (tube) is placed between the Right Ventricle and Pulmonary Artery to bypass the narrowing, obstruction and at another tunnel is created between the Left Ventricle and Aorta to allow blood flow and close VSD.

All of the above are open heart surgeries during which heart is stopped.

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