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This article provides a review of trends in modern practice in the management and outcome of transposition of the great arteries (TGA) from fetal until adult life. It focuses on simple transposition (isolated ventriculo-arterial discordance or D-TGA) with some references to transposition with a ventricular septal defect (VSD).
DIAGNOSIS IN FETAL LIFE
Antenatal diagnosis of TGA results in better clinical status before surgery,w1 w2 and improved postoperative outcome,1 w3 compared to those diagnosed postnatally. The diagnosis of D-TGA was infrequently recognised by obstetric sonographers in the era of the four chamber view. A detection rate <20% rises with an increased number of routine antenatal scans and a policy of careful training for two outlet echocardiographic views.2 w4 Regions of Paris achieved a detection rate of 72% between 1995 and 2000.3 Disappointingly, the rate is still around 20% in many first world centres.w5
Thus the majority of infants in most centres still present with cyanosis, typically in the first 2 or 3 days, and many require resuscitation. A high preoperative lactate is the most important predictor of poor developmental outcome, along with low gestational age,4 and seizures may occur in around 5% before surgery.w6
Infants with TGA may be at higher risk of cerebral damage than others because of chronically decreased oxygen delivery to the brain in fetal life. Oxygenated blood is preferentially streamed into the lower body and not into the brain as in the normal fetus. Supportive evidence originates from a study of cerebral metabolism in 10 stable infants with TGA before surgical correction, using proton magnetic resonance spectroscopy.5 Cerebral metabolism was altered specifically in the parietal white matter, suggesting a maturational delay, rather than an acute (post-natal) insult.
Key points 1: Diagnosis in fetal life
The fetus with TGA has chronic cerebral hypoxia due to the streaming of oxygenated blood away …