https://orcid.org/0000-0002-5831-7954
Abstract
We report the case of successful biventricular repair after left ventricular rehabilitation in an infant with transposition of the great arteries with an intact ventricular septum, pulmonary stenosis, a large atrial septal defect and a borderline small left ventricle (mitral annulus z-score: −3.6). This baby presented to us at 2 months of age after having a modified Blalock-Taussig shunt at another hospital. We restricted the atrial septal defect with the child on cardiopulmonary bypass. Ten weeks later, the mitral annulus z-score increased to −1.5, and the transpulmonary peak pressure gradient increased to 87 mmHg. Subsequently, we performed the aortic root translocation. The patient is currently an active 4-year-old boy.
This study was approved by the Konkuk University Medical Center Ethics Committee (KUMC 2022–05-017), which waived written informed consent.
A full-term baby, weighing 3.1 kg, was born at another hospital. He had complex cardiac anomalies, including transposition of the great arteries with an intact ventricular septum, pulmonary stenosis, an unrestricted atrial septal defect (ASD) and a borderline small left ventricle (LV). That hospital performed a modified Blalock-Taussig shunt with a 3.5-mm graft with the child on cardiopulmonary bypass 3 days later.
When the child was 2 months of age, the parents were advised by their hospital that the baby's next operation should be a bidirectional cavopulmonary shunt. Seeking a second opinion, they visited our service to ask if there was an alternative procedure for a 2-ventricle repair. The infant weighed 4.2 kg with 82% room air oxygen saturation. The data demonstrated a well-formed LV apex and well-functioning LV and mitral valve (MV) but a small mitral annulus (z-score: −3.6) (Fig. 1A, B). Moreover, an unrestrictive ASD was noted. We restricted the ASD using interrupted sutures from 15 mm to 4–5 mm using a Hegar dilator with the child under cardiopulmonary bypass. However, an immediate widening to 6 mm using the appropriately sized Hegar dilator was needed due to desaturation and acidosis (the oxygen saturation fluctuated, with a high of 88% and an FiO2 of 0.4 and a low approaching 70%). After 10 weeks, the mitral annulus size increased to a z-score of −1.5, and the transpulmonary valve peak pressure gradient from 60 mmHg to 87 mmHg (Video 1 and Supplementary Table S1). The patient weighed 5.2 kg with 80% oxygen saturation.
Two-dimensional echocardiogram at the end-diastolic phase, before (A, B) and after (C, D) the atrial septal defect restriction (asterisk), then 3 years after aortic root translocation (E, F). LV: left ventricle; RV: right ventricle.
Subsequently, we performed an aortic root translocation. The pulmonary valve was bicuspid with subvalvular fibrotic tissue, and the annulus was Hegar dilator size 4. After removing the most stenotic segment, an incision down to the interventricular septum facilitated our ability to introduce a Hegar size 8 into the LV outflow tract. Then, we mobilized the 2 main stem coronary arteries in a short segment. The aortic root was developed with a sleeve of right ventricle muscle, which matches up the widened interventricular septum without an additional patch. With the LeCompte manoeuvre, the main pulmonary artery was directly anastomosed to the right ventricular outflow tract using a transannular patch without a cusp anteriorly. The remnant ASD was closed. The early postoperative course was smooth with a short period of a low-dose vasodilator (milrinone) and 2 days on mechanical ventilation.
Cardiac computed tomography showed good alignment in both ventricular outflow tracts and good biventricular function 4 months postoperatively (Fig. 2). The latest echocardiogram revealed both ventricles to be well functioning (Fig. 1E, F and Video 1).
Contrast-enhanced computed tomogram before (A) and after (B) the aortic root translocation. Note the valvular and subvalvular pulmonary stenosis (* the subvalvular diameter of 6.2 mm) on preoperative images (A), which improves after aortic root translocation (the subvalvular diameter of 12.9 mm) (B). AAo: ascending aorta; LV: left ventricle; MPA: main pulmonary artery; RV: right ventricle.
Transthoracic echocardiogram before and after atrial septal defect restriction, then 3 years after aortic root translocation.
DISCUSSION
The surgical management of transposition of the cardiac arteries with pulmonary stenosis with or without a ventricular septal defect (VSD) is generally agreed upon [1, 2]; it includes a routine arterial switch operation with pulmonary stenosis relief, aortic root translocation, double-root translocation, réparation à l’ètage ventriculaire, or the Rastelli procedure. However, a small LV makes it a matter of triage on single versus biventricular repair.
Several situations may affect the adequacy of the LV as a systemic ventricle. First, in a heart with a concordant ventriculoarterial (VA) connection without a VSD and with a small MV, the small LV demonstrated adequate growth, mitigating the mitral inflow obstruction [3]. Second, with a discordant VA connection without a VSD, training the regressed LV by pressure overload was proposed as a guideline [4]. Third, in a complex heart with VSD and a borderline hypoplastic right or left ventricle, the growth of the ipsilateral ventricle by ASD restriction made the biventricular repair possible [5].
In this case, the combination of a discordant VA connection, no VSD, pulmonary stenosis, an unrestricted ASD and a small MV was unique and uncommon. In the fetal stage, pulmonary stenosis might train the LV by pressure overload, and the unrestricted ASD with a small mitral annulus would make the LV smaller than normal. Based on outside data, one might consider the LV inadequate as a systemic ventricle; therefore, the baby would have had a single ventricular physiology as recommended by the first hospital. However, the well-formed LV apex, good ventricular contractility and good MV leaflet motion with a small annulus encouraged us to try to challenge the volume of the small LV via ASD restriction.
Challenged volume in the morphologic LV may depend on the systemic–pulmonary shunt and final ASD size. In our experience, determining the precise size of the remnant ASD occurred via trial and error. Therefore, more data and experience sharing might be needed for solid decision making in determining the ASD size for this kind of complex anatomic substrate. A left atrial pressure line might be useful for immediate postoperative haemodynamic monitoring, although the Doppler gradient across the residual ASD could also help estimate the left atrial pressure. The relative size of the remnant ASD with respect to the increasing body surface area may decrease. And, more volume may be loaded into the LV, resulting in a higher transpulmonary pressure gradient. This scenario happened within 10 weeks after the ASD restriction in our case, leading to complete anatomic repair.
Our case may be another good example of the possibility of rescuing the borderline small LV through rehabilitation.
Funding
No funding was provided for this study.
Conflict of interest: none declared.
Data Availability
All data are incorporated into the article and its online supplementary material.
