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FIG 37.26 Magnetic resonance images from a 23-year-old patient after the arterial switch operation, demonstrating the origins of the right (R) and left (L) coronary arteries Fate of the Neoaortic Root, Valve, and Ascending Aorta In addition to the general concern that the pulmonary valve is not appropriately structured to fulfill its role as an aortic valve, two of its three sinuses will have been incised at the time of the arterial switch to accommodate the coronary arterial buttons These factors, combined with the recognized complication of dilation of the reconstructed aorta, place the patient at risk of neoaortic incompetence, which, in one study, was demonstrated in approximately half of adults previously corrected with the arterial switch procedure Nonetheless, at a mean age of 21 years, none was moderate or greater in severity and none required intervention for this concern.105 Echocardiography can usually assess valvar size and function with accuracy, although magnetic resonance imaging may also play a role, especially when acoustic windows are limited (Fig 37.27) Typically, regurgitation of the neoaortic valve is associated with dilation of the ascending aorta This may, in turn, reflect decreased distensibility of the aorta and augmented reflection of waves within it, as well as an abnormal angulation of the aortic arch after the arterial switch operation.119,120 Interestingly, ascending aortic stiffening has also been found in patients undergoing atrial switch procedures in which the aorta has not be mobilized.121 This raises the question of intrinsic abnormalities of the extracellular matrix in patients with transposition There are increasing reports of significant neoaortic valve dilation and insufficiency leading to surgical reintervention in the second and third decades of life.43 FIG 37.27 Magnetic resonance image from a patient after the arterial switch operation The relationships between the great vessels can be easily identified The right (RPA) and left (LPA) pulmonary arteries straddle the aorta (Ao), typical of the LeCompte maneuver The pulmonary arteries are widely patent Pulmonary Arteries Obstruction to QP is the most frequent residual anatomic problem after the arterial switch operation and is the most frequent indication for reoperation (Fig 37.28) Obstruction can occur at multiple levels Diffuse hypoplasia of the pulmonary trunk commonly results from inadequate mobilization of the pulmonary arteries, leading to tension on, and flattening of, the reconstructed pulmonary channel Circumferential narrowing at the anastomotic margins can cause discrete stenosis, whereas the right or left pulmonary arteries can themselves be stenotic in the setting of a LeCompte maneuver where they are draped over the aorta Such obstruction to QP accounted for more than 40% of all reoperations reported in a large series with an average duration of follow-up of 5 years.109 The majority of reoperations for pulmonary obstruction are required relatively early, within the first year after the arterial switch operation This commonly heralds the need for repeated reintervention Using limited coronary artery buttons as opposed to mobilization of the entire sinus of Valsalva may reduce the incidence of stenosis.122 FIG 37.28 Survival free of reoperation for survivors of the arterial switch operation (A) and hazard functions for reoperation (B) Dotted lines indicate 70% confidence interval (From Losay J, Touchot A, Serraf A, et al Late outcome after arterial switch operation for transposition of the great arteries Circulation 2001;104[suppl I]:I-121–I-126.)
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