Objectives. Myocardial blood flow (MBF) in children late after arterial switch operation (ASO) was investigated quantitatively by positron emission tomography (PET). Background. In children with transposition of the great arteries (TGA), ASO is widely accepted as the management of choice. The long- term patency of coronary arteries after surgical transfer to the neo-aorta, however, remains a concern. Methods. Twenty-two normally developed, symptom- free children were investigated by PET with nitrogen-13 ammonia at rest and during adenosine vasodilation 10 ± 1 years after ASO. A subgroup of 15 children (9 ± 1 years; group A) had simple TGA and underwent ASO within 20 days after birth while 7 (13 ± 3 years; group B) had complex TGA and underwent ASO and correction of associated anomalies later after birth. Ten young, healthy adults (26 ± 6 years) served as the control group. Results. Resting MBF was not different between groups. After correction for the rate- pressure product as an index of cardiac work, younger children of group A had significantly higher MBF at rest compared to healthy adults (102 ± 29 vs. 77 ± 16 ml/100 g/min; p = 0.012) while flow in group B was not different from the other groups (85 ± 22 ml/100 g/min; p = NS). Hyperemic blood flows were significantly lower in both groups after ASO compared to normals (290 ± 42 ml/100 g/min for group A, 240 ± 28 for group B, 340 ± 57 for normals; p <0.01); thus, coronary flow reserve was significantly lower in both groups after ASO compared to healthy adults (3.0 ± 0.6 for group A, 2.9 ± 0.6 for group B, 4.6 ± 0.9 for normals; p <0.01). Conclusions. Blood flow measurements suggest decreased coronary reserve in the absence of ischemic symptoms in children late after arterial switch repair of TGA. The global impairment of stress flow dynamics may indicate altered vasoreactivity; however, the prognostic significance of these findings needs to be determined.
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