Persistent neo-aortic root dilatation and aortic valve insufficiency after arterial switch operation following prior pulmonary artery banding

Abstract

Although there have been great improvements in the short- and medium-term outcomes of the arterial switch operation (ASO) for transposition of the great arteries (TGA), some complications including pulmonary artery stenosis, aortic valve insufficiency, and aortic root dilatation have also been reported. After ASO, the original pulmonary root and valve, which function in the systemic position as the neo-aortic root and valve respectively, are exposed to the systemic blood pressure, resulting in aortic root dilatation and valve insufficiency in some patients. One of the risk factors for these complications is a history of prior pulmonary artery banding (PAB). Complex TGA anatomy, including transposition of the great arteries and ventricular septal defect (TGA-VSD) or double outlet right ventricle and ventricular septal defect (DORV-VSD), is also an independent risk factor for neo-aortic dilatation and aortic valve regurgitation. Aortic valve and root replacement is sometime necessary for the patients with these pathologies long-term after ASO. Here, we present a patient who had persistent aortic sinus dilatation and aortic valve insufficiency since ASO and necessitating aortic root and valve replacement 15 years after ASO preceded by PAB. The patient underwent Bentall operation and his clinical course was favorable. Histological findings after root replacement revealed no remarkable structural difference between neo-aortic wall (originally pulmonary artery) and original aortic wall.

Introduction

Since the introduction of the arterial switch operation (ASO) in 1975 [1], it has been widely embraced as an acceptable standard treatment for patients with transposition of the great arteries (TGA). A plethora of studies dealing with the long-term outcomes of ASO have revealed late complications, including branch pulmonary artery stenosis, aortic valve insufficiency, and aortic root dilatation that might necessitate surgical intervention in some patients [2–4]. A number of studies have explained certain etiologies of these pathologies as well as some of their potential risk factors [5]. The timing of surgical intervention in patients with aortic valve insufficiency and root dilatation after ASO remains controversial, because not only one is hesitant to implant artificial valves and grafts in young children and adolescents, but also it is likely that these patients potentially have large pulmonary trunk which would be used as systemic outflow after ASO. The left ventricular volume is not so dilated and is often preserved in these patients with moderate aortic valve regurgitation. The pulmonary trunk is originally dilated in patients with complex anatomy such as transposition of the great arteries and ventricular septal defect (TGA-VSD), double outlet right ventricle and ventricular septal defect (DORV-VSD), and the patients who receive pulmonary artery banding (PAB) as palliation. This originally dilated pulmonary trunk is used as neo-aortic trunk after ASO. Because of this etiology, the risk of dilated aortic root rupture or dissection is uncertain after ASO. In the present study, we report a case of aortic root and valve replacement for uniquely shaped aortic root dilatation, valve insufficiency, and left ventricular enlargement late after ASO and prior PAB. The validity of surgical intervention in these patients is propounded.

Case report

The patient was a 16-year-old boy who had been diagnosed with TGA and ventricular septal defect (VSD). PAB had been performed during the neonatal period followed by the ASO at 8 months of age. The following strategies were adopted by the surgeon: Trap door technique was used as coronary artery implantation procedure and Lecompte maneuver was used for pulmonary artery reconstruction, as well in the ASO. At the time of ASO after PAB, there was already a large discrepancy between the diameter of aortic and pulmonary trunk. Neo-aortic root dilatation was also observed 3 years after the ASO, which led to further aortic root dilatation (Fig. 1A, B) and valve insufficiency at the age of 12 years. He had a history of echocardiographically detected moderate aortic regurgitation, but left ventricular function was preserved without left ventricular enlargement since ASO. When the patient was 16 years old, the aortic root dilatation was still present (Fig. 1C, D), with a further deterioration in his aortic valve insufficiency and left ventricular enlargement (left ventricular end diastolic/systolic dimensions—55.3/37.6 mm, respectively) on echocardiography, which necessitated surgical intervention. Hence, the Bentall operation was performed at that time. During the surgery, the coronary arteries were reconstructed according to the Piehler method. The aortic trunk was replaced with an artificial graft and mechanical valve. The artificial graft was interposed between the main pulmonary artery and its right branch. The postoperative clinical course was uneventful, and histological examinations after the operation revealed no remarkable differences between the originally pulmonary arterial wall (neo-aortic wall) and the original aortic wall (just proximal to aortic arch) and focal myxoid degeneration was found in each aortic wall. He was discharged from the hospital without any complications.

Fig. 1.

A, B Computed tomography image 12 years after arterial switch operation already showed characteristic aortic root (original pulmonary trunk) dilatation. C, D Computed tomography image 16 years after arterial switch operation showed the same shape of aortic root (original pulmonary trunk). Aortic dilatation and moderate aortic regurgitation were already observed soon after ASO. Aortic sinus aneurysm and valve insufficiency had been preserved since ASO until Bentall operation. ASO, aortic switch operation

Discussion

The ASO has been a standard surgical treatment for TGA, and favorable long-term outcomes have been reported. In this procedure, the original pulmonary valve and root are preserved to function in the systemic position during early stages of life with the assumption that their structures will adapt to the systemic blood pressure. Nonetheless, some studies have reported late complications like pulmonary artery stenosis, aortic valve insufficiency, and aortic root dilatation [5, 6]. Although the total amount of reoperations on the neo-aortic root and valve are still low, neo-aortic operations, including aortic root and valve replacement, are reported to be the second most common reoperations [7]. As a potential risk factor for late aortic valve insufficiency and root dilatation, PAB is presented in these papers. High pressure induced by PAB in pulmonary artery may cause pulmonary artery dilatation. The complex TGA anatomy, including TGA-VSD or DORV-VSD, is an independent risk factor for neo-aortic dilatation and aortic valve regurgitation as well [8, 9]. In patients with these anatomies, pulmonary blood flow is increased and pulmonary artery is relatively larger than aorta before ASO. These reports also revealed that a disproportionate increase of neo-aortic size and aortic valve insufficiency occurred in the first year of ASO. Few histological differences before ASO have been reported in the aortic and pulmonary vascular walls in patients with TGA [10]. In this paper, thinner vascular wall and fewer elastic laminae in the original pulmonary artery were revealed before ASO. These histological findings may be related to aortic root dilatation over long time after ASO for some patients. However, etiology of aortic valve dysfunction is not decisive. Aortic root dilatation and enlargement of aortic valve annulus may be related to valve malfunction. From these points of view, aortic root dilatation and valve insufficiency should be concerning, although they are rare complications.

Our patient exhibited a pear-shaped dilatation of the aortic sinus of Valsalva (original pulmonary trunk) and aortic valve insufficiency (original pulmonary valve) 12 years after PAB followed by the ASO. He had already presented with dilated aortic root and aortic valve insufficiency 3 years after the ASO as well. The large discrepancy between the diameter of aortic and pulmonary root at the time of ASO after the PAB was already observed. The ratio between the dilated aortic root and the ascending aorta had remained unchanged and moderate aortic regurgitation had persisted throughout the follow-up period since ASO. Neo-aortic root dilatation and valve insufficiency had been observed consistently. Additionally, there was no typical histological finding in neo-aortic wall (original pulmonary arterial wall), compared to original aortic wall (just proximal to the aortic arch) in our case, although it was revealed after aortic root and valve replacement. PAB might have caused the sinus dilatation and valve insufficiency in previous period before ASO. TGA-VSD or TGA-DORV anatomy might also have a potential for aortic root dilatation. There was no apparent neo-aortic valve deformation, as aortic root and annulus dilatation can affect neo-aortic valve dysfunction.

Surgical intervention is indicated for aortic valve insufficiency and aortic root dilatation even in patients without congenital heart disease. However, the timing of intervention is controversial in patients with congenital heart disease, because patients with pathologies such as tetralogy of Fallot or TGA potentially have a large aortic root and aortic valve dysfunction to some degree [7] and no aortic dissection and rupture have been reported to date. Although, according to the guidelines of aortic root surgery, if root diameter reaches 55 mm, root replacement should be indicated [11]; anatomical complexity and surgical difficulties including artificial valve implantation and root replacement in children further complicate the decision on the timing of surgical intervention. Re-do surgery is challenging and artificial valve–related complication, including hemorrhage, infarction, and valve malfunction, should be considered with caution for the pediatric patients.

The case presented herein showed aortic valve insufficiency with moderate aortic regurgitation and persistent root dilatation since PAB followed by the ASO. This type of aortic root dilatation after ASO may have different clinical course from other kind of critical aneurysm without congenital heart disease. Thus, an elective and prudent surgical intervention should be considered for the young patients with aortic valve insufficiency and root dilatation who cannot be implanted with artificial valves and grafts. For the patients with aortic valve insufficiency due to aortic root and annulus dilatation, an aortic valve–sparing operation is one of the choices, but surgical outcome is not certain [12]. The superiority of valve repair techniques has been stressed in the literature [13], but because etiology of aortic valve insufficiency of the patients with congenital heart disease is uncertain and valve-sparing techniques are not so reliable, we decided to perform Bentall operation at a time when adequate size artificial valve could be implanted and left ventricular function was not impaired although left ventricular volume enlargement was observed due to moderate aortic valve regurgitation. It might be important to consider the size of neo-aortic diameter when surgical intervention is indicated but in terms of clinical course of neo-aortic dilatation in our case, we would not have chosen neo-aortic root replacement for persistent aortic root dilatation, if only neo-aortic root dilatation had been observed.

Funding

None.

Data Availability

The authors confirm that the data supporting the findings of this study are available within the article [and/or] its supplementary materials.

Declarations

Ethical approval

Our institutional review board made the decision that ethics approval is not needed for this case report.

Consent to participate and for publication

Informed consent was obtained from the patient and the patient’s parents.

Conflict of interest

The authors have no relevant financial support to disclose.

Human and animal right statement

Any animals were not included in this study and any procedure and analysis used in this report were in accordance with the ethical standards of the responsible committee on human experiment.