Midterm assessment of the reconstructed arteries after the arterial switch operation.

Background: The arterial switch operation is the preferred treatment for transposition of the great arteries (TGA), but there are concerns on the fate of the neoarterial trunks.

Methods: Ninety-three children were reviewed for functional and morphologic assessment of both reconstructed arteries after the arterial switch operation. Longitudinal analysis focused on neoaortic valve function, neoaortic obstruction, and neopulmonary stenosis as well as on the time-related size changes of both roots, with its clinical implications.

Results: Within a mean follow-up of 4.8 +/- 3.9 years, aortic regurgitation of 2 or greater developed in 10% in TGA with intact ventricular septum (IVS) versus 23% in TGA with ventricular septal defect (VSD). A VSD and major pulmonary to aortic annulus size discrepancy were main precursors of early neoaortic valve dysfunction, whereas development of aortic regurgitation of 2 or greater was additionally promoted by the duration of follow-up. Presence of a VSD enhanced neoaortic root enlargement, resulting in a mean root z-score of 3.25 in TGA/VSD versus 1.96 in TGA/IVS. Root dilation was more severe in case of aortic regurgitation of 2 or greater (z = 3.38). Neoaortic obstruction occurred in 8%, mostly at the neosinotubular anastomosis, and correlated with prior pulmonary to aortic ratio greater than 1.5. Concerning the neopulmonary tract, increased flow velocity was observed in 24%, primarily at the supravalvular level. Two patients with pulmonary annulus hypoplasia (z < -2) required early reintervention. Regarding clinical outcome, freedom from reintervention at 1, 5, and 10 years was, respectively, 98%, 96%, and 96% for TGA/IVS, versus 65%, 63%, and 63% for TGA/VSD. A VSD and aortic arch obstruction were significant predictors for reintervention.

Conclusions: After arterial switch operation, the neoaortic root is usually enlarged, but with a growth pattern comparable to that of a normal population. The association of a VSD and major arterial root size discrepancy predisposes to both neoaortic valve dysfunction and root enlargement. Severe root dilation appears to be closely related to significant neoaortic valve regurgitation, mainly as a result of a time-depending and reciprocal process. Neopulmonary stenosis is a frequent finding, but rarely has clinical consequences. Because the factor "time" is the principal determinant of late neoaortic valve dysfunction and root dilation, strict serial surveillance after arterial switch operation is mandatory.