Anatomical Correction of Transposition of the Great Arteries at the Arterial Level with Dacron Patch Closure of Multiple Ventricular Septal Defects under Integrated Extracorporeal Membrane Oxygenation: A Video Presentation

INTRODUCTION

Transposition of the great arteries is a congenital cardiac malformation that results from the abnormal chamber connections of atrioventricular concordance and ventriculoarterial discordance (SDD). It is generally classified as a type of conotruncal abnormalities, a group of abnormalities that has a common theme of deranged development of the cardiac outflow tract. In D-transposition, the aorta is anterior and to the right of the pulmonary artery. This pattern results in the systemic and pulmonary circulations occurring in parallel rather than in series.^[1,2]

Transposition of the great arteries accounts for 9.9% of infants with congenital heart disease or 0.206/1000 live births.^[3] These patients are subdivided into those with intact ventricular septum (50%), ventricular septal defect (25%), and ventricular septal defect with pulmonary stenosis (25%).^[1,2] Other associated cardiac anomalies include persistent ductus arteriosus and coarctation of the aorta.^[4,5]

The ventricular septal defects are classified based on the surgical anatomy of the interventricular septum and the morphologic definitions as published by Soto et al.^[6] In patients with transposition of great arteries, because of the surgical difficulties that are encountered for ventricular septal defects located at the trabecular septum, Serraf et al. divided the trabecular septum into three components: high (an anterior), mid (centered by the moderator band), and low (or apical).^[7]

Thus, the interventricular septum is composed of six components: Perimembranous, inlet muscular, outlet muscular, and the three trabecular muscular components.^[8,9] The definition of multiple ventricular septal defects is based on the involvement of at least two out of six components of the interventricular septum.^[8,9]

In 1999, Seddio et al. defined “Swiss-Cheese” septum as a localized or general lack of compaction of the interventricular septum.^[10] In 1995, Houyel et al. described the relationship of the great arteries in cases of transposition of great arteries with ventricular septal defect.^[11] In 76% of cases, the aorta and pulmonary artery were in an anteroposterior relationship. A side-by-side relationship was observed in 20% and l-malposition of the aorta was present in 4% of cases.^[12]

Coronary arterial anomalies are more frequent in the transposition of great arteries in ventricular septal defects. Many classification systems have been used to describe the coronary anatomy in transposition of the great arteries.^[5,12-14] The Leiden classification is most commonly used.^[12-16] The most common coronary pattern in D-transposition of the great arteries (68%) consists of the left main coronary artery arising from the leftward coronary sinus giving origin to left anterior interventricular and circumflex coronary arteries. The right coronary artery arises from the right posterior sinus. In 20% of cases, the circumflex coronary arteries arise from the right coronary artery and pass behind the pulmonary artery. In 4.5% of cases, a single right coronary artery arises from the right posterior sinus or a single left coronary artery from the leftward coronary sinus.^[17] Intramural coronary arteries that proceed in the aortic wall for a distance before exiting to the epicardial surface, single coronary ostium, or separate ostia have been described.^[16] The inverted origin of the coronary arteries and inverted origin of the circumflex and right coronary arteries have been described in 3% and 7% of cases, respectively.^[18]

Despite advances in pre-operative diagnosis, improved surgical techniques, and perioperative care, significant mortality still exists in patients undergoing arterial switch operations with multiple ventricular septal defect closure.^[19-21]

Although the spectrum of ventricular septal defect in the transposition of great arteries is different from that of hearts with ventriculoarterial concordance, the principles of surgical repair are nearly similar.^{[7-11,20,22,23]}

There remains considerable controversy regarding the optimal management of these patients with transposition of great arteries and multiple ventricular septal defects.^{[7-11,20,22,23]} Although the present practice is to perform early anatomical repair, the ideal time of surgical intervention, the ideal surgical approach, and one versus two-stage management remains controversial. At present, in patients with transposition of great arteries and multiple ventricular septal defects, the presence of associated aortic arch obstruction without severe hypoplasia, and “Swiss Cheese” defects, a preliminary pulmonary artery banding may be the preferred option.^[7,20-24] The presence of aortic and/or subaortic stenosis, coronary artery coursing between the aorta and pulmonary artery, and closing ductus with a restricted atrial septal defect are contraindications for pulmonary artery banding as initial palliation.

In 1999, Conte et al. reported internal pulmonary arterial band placement to reduce the risk of pulmonary arterial distortion and coronary compression.^[25] An accurate pre-operative diagnosis is essential for a satisfactory outcome.^{[7-10,20,22-24]}

Although the atrial baffle procedures are associated with a low mortality rate (<5%), they are plagued by long-term complications, namely, baffle leak, supraventricular and ventricular dysrhythmias, systemic venous pathway obstruction, tricuspid valve insufficiency, and right ventricular (RV) failure.^[26-28] The arterial switch operation has largely replaced atrial baffle procedures with excellent mid-term and long-term results.^[26-28] At present, the indications of atrial baffle procedures are limited and are institutionally dependent.^[26-28]

The anatomical correction at the arterial level is the procedure of choice. Improved techniques of coronary transfer, myocardial protection, and neogreat vessel reconstruction have resulted in improved survival statistics that compare favorably with the atrial baffle procedures.^[29-31] Anomalies of the coronary arterial origin and course in transposition of great arteries are common and various innovative techniques have been employed for coronary artery transfer during arterial switch operation.^[29-31]

Numerous attempts have been made to extend the boundaries of the atrial switch operation in children presenting late with intact ventricular septum or restrictive ventricular septal effects and regressed left ventricle. Literature is divided on the usefulness of elective institution of mechanical circulatory support, such as extracorporeal membrane oxygenation (ECMO) or left ventricular assist device (LVAD) for late presenters of d-transposition.^[32-37] Published data support that a primary atrial switch operation can safely be performed as a primary procedure up to 2 months of age, and above this age, left ventricular (LV) mass and LV mass to LV end-diastolic volume ratio may orient toward rapid two-stage or primary atrial switch operation up to 2 years of age. Beyond 2 years, an atrial switch procedure should be considered.^[33-37]

The decision to perform a primary atrial switch operation in our center is based on the values of LV mass >35 g/m² and when between 25 and 35 g/m² on the value of LV mass/LV end-diastolic volume ratio >1.2, LV posterior wall thickness >4 mm in diastole and absence of “D” or “banana” shaped LV cavity.^[34-37]

However, the above-mentioned echocardiographic criteria to calculate LV mass assume the LV to be either spherical or prolate ellipsoid in shape.^[38] However, in transposition, the regressed left ventricle is either “banana” or “D” shaped. Therefore, the criteria of LV mass index <35 g/m² should be used with caution in labeling the regressed left ventricle. The other indications used in our institutions, as well as by others for retraining the regressed left ventricle have been an LV/RV pressure ratio of <0.6 for children more than 3 months or <0.5 in those <3 months.^[39,40]

We have incorporated ECMO in the cardiopulmonary bypass (CPB) circuit as an integrated ECMO – CPB circuit to reduce the cost, minimize the time lag, initiate ECMO to enable LV retraining under normoxemia and controlled loading, avoid low cardiac output state and surgical asepsis.

Several investigators in recent times have used LVAD in the postoperative period after delayed ASO.^[41-43] T-stage ASO although being practiced in several institutions is fraught with its own set of complications with higher interstage mortality and morbidity from neoaortic regurgitation and LV diastolic dysfunction due to subendocardial ischemia.^[44]

The arterial switch operation restores LV to aortic continuity and has not been associated with atrial baffle-related complications as enumerated above. The mid-and long-term results of patients undergoing arterial switch operation are encouraging. In the congenital heart surgeon study on 513 infants (transposition of great arteries with intact ventricular septum, n = 385; transposition of great arteries with ventricular septal defect, n = 129), the 1-month, 1-year, and 5-year survival rates were 84%, 82%, and 82%, respectively.^[45,46] The largest series on 1095 patients from a single institution with long-term follow-up was reported in 2001. At a mean follow-up of 5 years, hospital mortality was 8.6%, survival was 89% at 1 year, and 88% at 10 and 15 years.^[45]

SURGICAL TECHNIQUES

RESULTS

The child was electively placed on integrated ECMO and dopamine 5 μg/kg/min, dobutamine 5 μg/kg/min, adrenaline 0.01 μg/kg/min, and nitroglycerine 0.5 μg/kg/min for 72 h. Subsequently, the child was weaned off ECMO support and discharged home on the 20^th post-operative day. Postoperatively, the child is asymptomatic, on nil medications, and not in cardiac failure, with Ross clinical score of 2. Echocardiographically, the child has normal biventricular function without any residual anatomical lesions.

CONCLUSION

Anatomical correction of transposition with concomitant closure of multiple ventricular septal defects as a one-stage procedure with integrated ECMO is an expedient, safe, and effective surgical strategy, for late presenters beyond 4 weeks of age. The large left-to-right shunt and pulmonary hypertension resulting from the multiple ventricular septal defects (and from the patent arterial duct) may obscure the presence of magnitude of the smaller ones, especially located in the high and mid-trabecular septum. Thus, an accurate pre-operative diagnosis and intraoperative systemic examination are crucial for a successful outcome.