Dextro-transposition of the great arteries (or d-Transposition of the great arteries; abbreviated dextro-TGA or d-TGA) is a potentially life-threatening birth defect in the large arteries of the heart. The primary arteries (the aorta and the pulmonary artery) are transposed. A d-TGA baby will exhibit indrawing beneath the ribcage and "comfortable tachypnea" (rapid breathing); this is likely a homeostatic reflex of the autonomic nervous system in response to hypoxic hypoxia. The infant will be easily fatigued and may experience weakness, particularly during feeding or playing; this interruption to feeding combined with hypoxia can cause failure to thrive.
Simple and complex d-TGA
d-TGA is often accompanied by other heart defects, the most common type being intracardiac shunts such as atrial septal defect (ASD) including patent foramen ovale (PFO), ventricular septal defect (VSD), and patent ductus arteriosus (PDA). Stenosis of valves or vessels may also be present.
When no other heart defects are present it is called 'simple' d-TGA; when other defects are present it is called 'complex' d-TGA.
Although it may seem counterintuitive, complex d-TGA presents better chance of survival and less developmental risks than simple d-TGA, as well as usually requiring fewer invasive palliative procedures. This is because the left-to-right and bidirectional shunting caused by the defects common to complex d-TGA allow a higher amount of oxygen-rich blood to enter the systemic circulation. However, complex d-TGA may cause a very slight increase to length and risk of the corrective surgery, as most or all other heart defects will normally be repaired at the same time, and the heart becomes "irritated" the more it is manipulated.
Treatment
Life-saving heart surgery is always required. It is ideally performed on an infant between 8–14 days old.
The heart and vessels are accessed via median sternotomy, and a cardiopulmonary bypass machine is used; as this machine needs its "circulation" to be filled with blood, a child will require a blood transfusion for this surgery. The procedure involves transecting both the aorta and pulmonary artery; the coronary arteries are then detached from the aorta and reattached to the neo-aorta, before "swapping" the upper portion of the aorta and pulmonary artery to the opposite arterial root. Including the anaesthesia and immediate post operative recovery, this surgery takes an average of approximately six to eight hours to complete.
Some arterial switch recipients may present with post-operative pulmonary stenosis, which would then be repaired with angioplasty, pulmonary stenting via heart cath or median sternotomy, and/or xenograft.
thumb|right|One day post-operative (Jatene procedure) d-TGA + VSD neonate
Atrial switch
In some cases, it is not possible to perform an arterial switch, either because of late diagnosis, sepsis, or a contraindicative coronary artery pattern. In the case of sepsis or late diagnosis, a delayed Arterial Switch can sometimes be made possible by PAB, which may also require a concomitant construction of an aortic-to-pulmonary artery shunt. Both methods involve creating a baffle to redirect red and blue blood flow to the appropriate artery. Since the late 1970s the Mustard procedure has been preferred.
Post-operative
Following corrective surgery, but prior to cessation of anaesthesia, two small incisions are made immediately below the sternotomy incision which provide exit points for chest tubes used to drain fluid from the thoracic cavity, with one tube placed at the front and another at the rear of the heart.
The patient returns to the ICU post-operatively for recovery, maintenance, and close observation; recovery time may vary, but tends to average approximately two weeks, after which the patient may be transferred to a Transitional Care Unit (TCU), and eventually to a cardiac ward.
Post-operative care is very similar to the palliative care received, with the exception that the patient no longer requires PGE or the surgical palliation procedures. Additionally, the patient is kept on a cooling blanket for a period of time to prevent fever, which could cause brain damage. The sternum is not closed immediately which allows extra space in the thoracic cavity, preventing excess pressure on the heart, which swells considerably following the surgery; the sternum and incision are closed after a few days, when swelling is sufficiently reduced.
Follow-up
The infant will continue to see a cardiologist on a regular basis. Approximately one million people worldwide are currently living with a CHD.Having a child with a CHD increases an individual's chances of having another child with a CHD from 1% to 3%. Subsequent children born with a CHD increase that individual's chances further.
See also
- Levo-Transposition of the great arteries
- Transposition of the great vessels