Introduction
Patients with unbalanced atrioventricular septal defect, where the common atrioventricular valve is positioned more over one ventricle than the other, account for approximately 10% of the total atrioventricular septal defect patient population. In the case of unbalanced atrioventricular septal defect, there is a significant possibility of hypoplasia in the contralateral ventricle, and the degree of hypoplasia can vary. Reference Cohen and Spray1 When an unbalanced atrioventricular septal defect patient is considered to have a functional single ventricle, the consideration for single-ventricular palliation arises. Reference Owens, Gomez-Fifer and Gelehrter2 However, there is currently no consensus on criteria to determine whether to pursue single-ventricular palliation or biventricular repair.
Case report
A male newborn, diagnosed prenatally with atrioventricular septal defect and coarctation of the aorta was born via emergency caesarean section at full term due to deceleration. Initial echocardiography revealed an unbalanced atrioventricular septal defect with a small left ventricle, moderate degree of atrioventricular valve regurgitation, coarctation of the aorta, and right isomerism. CT was also performed, which confirmed the presence of a vascular ring with a retroesophageal circumscribed aorta. At the age of 5 days, the patient underwent the first surgery, which included coarctoplasty, vascular ring relief, atrioventricular valve repair through coaptation sutures, and pulmonary artery banding. Owing to the inadequate left ventricle size for biventricular repair, the initial plan was a staged approach towards the Fontan procedure.
The day after surgery, low cardiac output syndrome occurred, and insertion of central venoarterial extracorporeal membrane oxygenation was performed. However, the patient’s condition improved afterwards, and venoarterial extracorporeal membrane oxygenation weaning was performed 4 days later. We proceeded with ventilator weaning, but laboured breathing persisted, and effective weight gain remained elusive. Serial echocardiography revealed progression of left ventricle outflow tract obstruction, and the echocardiography performed at 3 months of age showed a narrow left ventricle outflow tract with a confirmed mean pressure gradient of 9.65 mmHg. Therefore, a modified Damus–Kaye–Stansel procedure was performed to increase systemic flow around 3 months of age, creating a surgical aortopulmonary window (Figure 1).
Figure 1. Surgical illustration of a modified Damus–Kaye–Stansel procedure.
After the modified Damus–Kaye–Stansel procedure, systemic perfusion increased, leading to improvement in cardiomegaly and pulmonary oedema. The post-operative course was favourable, with successful ventilator weaning and appropriate body weight gain. Serial echocardiographic monitoring revealed increasing trends in both left ventricular internal dimension at end-diastole (LVIDd) and the diameter of the mitral valve (MV) annulus (Figure 2). No definite left ventricle outflow tract obstruction was observed. Both ventricular functions were good, and atrioventricular valve regurgitation was trivial. By the age of 7 months, cardiac MRI was performed for left ventricle volume measurement, revealing an left ventricle end-diastolic volume of 20.4 mL (index = 65.8 mL/m2).
Figure 2. Graphs depicting changes in ( a ) MV annulus and ( b ) LVIDd, four-chamber views of echocardiography ( c ) before Damus–Kaye–Stansel procedure and ( d ) 4 months after Damus–Kaye–Stansel procedure.
After a comprehensive evaluation of the results, biventricular repair was determined to be feasible. Therefore, biventricular repair was performed at the age of 7 months. Atrioventricular septal defect repair was performed using a modified one-patch technique. The previous Damus–Kaye–Stansel and pulmonary artery internal banding were removed. Echocardiography performed after biventricular repair showed a balanced size and satisfactory systolic function of both ventricles. The MV annulus measured 9.5 mm (z-score = 12.98), with mild-to-moderate mitral regurgitation and no mitral stenosis. The patient recovered well after biventricular repair and was discharged at the age of 9 months.
Informed consent was provided by the parents on behalf of the patient, and the study was approved by the hospital’s institutional review board (approval no.: H-2403-005-1515).
Discussion
This patient experienced increases in left ventricle volume and MV size following the modified Damus–Kaye–Stansel procedure. Our centre has previously reported cases in which regression of left ventricle outflow tract obstruction occurred following the Damus–Kaye–Stansel procedure, leading to the implementation of staged biventricular repair. In that case report, two patients with Taussig–Bing anomalies and subaortic stenosis underwent initial palliation through the Damus–Kaye–Stansel procedure along with a modified Blalock–Taussig shunt. Subsequently, after observing aortic valve growth and regression of subaortic stenosis, the next surgery involved Damus–Kaye–Stansel take-down and intraventricular repair. Reference Lim, Kim and Lee3 While the exact mechanism remains uncertain, there is a possibility that the increase in forward flow and a reduction in pressure gradient may have facilitated the growth of the ventricle and regression of left ventricle outflow tract obstruction. In cases of atrioventricular septal defect, anatomical factors such as reduced inlet and increased outlet portions of the left ventricle, as well as the anterior displacement of the left ventricle outflow tract, can contribute to the development of subaortic stenosis. Reference Gallo, Formigari and Hokayem4 Timely palliative procedures may help prevent the progression of left ventricle outflow tract obstruction.
van Son et al. suggested that in cases of right-dominant unbalanced atrioventricular septal defect, a pre-operative left ventricle volume of ≥15 mL/m2 enables biventricular repair. Reference van Son, Phoon and Silverman5 The atrioventricular valve index, introduced by Cohen, is determined through echocardiographic measurement of the atrioventricular valve above each ventricle and is represented as the ratio of the left to right valve areas. An atrioventricular valve index <0.67 indicates that a single-ventricular repair approach may be suitable. Reference Cohen, Jacobs and Weinberg6 However, there is currently no consensus on the criteria to determine whether to pursue single-ventricular palliation or biventricular repair. Our centre determines the decision for biventricular repair based on a comprehensive evaluation of not only left ventricle size but also biventricular function, atrioventricular valve morphology, and left ventricle shape. As in this case, it should be considered that in patients with a borderline ventricular size, the left ventricle and MV diameters can increase after a single-ventricular palliation.
The patient has been developing normally up to the current age of 7 years. Recent echocardiograms showed no abnormalities other than a mild-to-moderate degree of MV regurgitation, which did not worsen. Periodic follow-up in the outpatient clinic is necessary to monitor whether valve regurgitation is progressing or if there is any occurrence of left ventricle outflow tract obstruction.
Conclusion
In patients with unbalanced atrioventricular septal defect and borderline ventricular size, staged biventricular repair may be feasible after single-ventricular palliation as the ventricle grows.
Financial support
None.
Competing interests
None.
IRB approval
03/07/2024, H-2403-005-1515.
Informed consent statement
Written informed consent was obtained for the patient in this case report.
