In this anomaly, the aorta arises from the morphological right ventricle (RV), and the pulmonary artery arises from the morphological left ventricle (LV) (ie, there is ventriculoarterial discordance). Complete transposition of the great arteries is also known as d-TGA; the “d-” refers to the dextroposition of the bulboventricular loop (ie, the position of the RV, which is on the right side). The aorta also tends to be on the right and anterior, and the great arteries are parallel rather than crossing as they do in the normal heart( Hornung TS, Derrick GP etal,2002)
D-TGA is one of the most common cyanotic defects seen in newborns, and when the ventricular septum is intact, it is usually cyanotic in the first day of life
Levin DL, Paul MH etal,1997 ).)
If circulatory mixing occurs via a patent ductus, physiological closure of the ductus causes abrupt cyanosis and clinical deterioration. Cyanotic babies may be treated percutaneously with a Rashkind atrial balloon septostomy to create a more sizable atrial septal defect, which may dramatically improve their oxygenation until definitive surgery can be performed(Miller WW,1996).
Atrial switch procedure:
The first atrial switch procedure was performed by Senning in 1958(Somerville J..,1999).
and involves the creation of an atrial baffle from autologous tissue to direct the venous return to the contralateral atrioventricular (AV) valve and ventricle. Thus, deoxygenated blood from the vena cavae is directed to the mitral valve and LV and thence to the pulmonary artery, and pulmonary venous blood is directed into the morphological RV and into the aorta. An alternative operation was subsequently developed by Mustard, who excised the atrial septum and used synthetic material to create the baffle ( Goncalves A ,1999). .
Sometimes an atrial switch is preceded by either the Rashkind balloon atrial septostomy or surgical atrial septectomy( Blalock A, Hanlon CR,1990)
Both atrial switch procedures provide excellent midterm clinical results but in the long term are associated with important sequelae.
Late development of both atrial bradyarrhythmias and tachyarrhythmias is a recognized late complication of atrial baffle surgery and is more likely to occur with longer follow-up( Warnes CA, Somerville J,1997).
Late RV dysfunction is a recognized outcome after the Mustard orSenning procedures because the RV is still the systemic ventricle, Tricuspid regurgitation often coexists, and both lesions increase the propensity for atrial arrhythmias (Dos L, Teruel L, Ferreira IJ etal,2005).
Pulmonary hypertension is a serious complication of atrial switch repairs for d-TGA and occurs in ≈7% of those who survive to adulthood(Kammeraad JA, van Deurzen CH, Sreeram N, etal 2004) The exact cause is not completely clear, but patients appear more likely to develop pulmonary vascular disease when undergoing operation at >2 years of age.( Roos-Hesselink JW,2004)
Arterial Switch Procedure
This operation restores the normal anatomic arrangement of the circulation and, as such, is a more attractive physiological long-term option. From its first description by Jatene in 1976, (Jatene AD, Fontes VF, Paulista PPetal,1976) it has steadily become the procedure of choice when the anatomy is appropriate and is usually performed in the first month of life. It involves transection of the great arteries above the sinuses and detachment of the coronary arteries along with a “button” from the aortic wall. The great arteries are then switched into their new position, with the pulmonary artery brought forward anterior to the aorta and the coronary buttons sutured into the “neoaorta.”
Adult survivors of this procedure are only now appearing in adult congenital heart disease clinics. Complications include distortion of the RV outflow tract and pulmonary arteries and dilatation of the neoaortic root with aortic regurgitation. Coronary stenoses may also occur and cause sudden death or myocardial infarction. (Bonnet D, Bonhoeffer P, Piechaud JF etal,1996). Other coronary stenoses may require surgical or catheter intervention( Prifti E, Bonacchi M, Luisi SV, Vanini V.,2002) Lifetime follow-up is clearly warranted.
This operation is used when d-TGA coexists with a large subaortic VSD and pulmonary stenosis. A patch is placed to direct blood from the LV through the VSD to the aorta. The pulmonary valve is oversewn, and continuity is established between the RV and the pulmonary artery by means of a valved conduit . This operation has the advantage that the LV functions as the systemic ventricle, but conduit degeneration and stenosis are inevitable, necessitating reoperation with all of its attendant risks. Atrial and ventricular arrhythmias are frequent, and sudden death may occur, particularly when significant conduit obstruction exists. RV and LV failure also may occur. Regular clinical and echocardiographic surveillance is necessary, and the development of arrhythmias should prompt a detailed evaluation of the hemodynamics.(Wallace RB, McGoon DC, 2003)