EXPLANATION


Double-outlet right ventricle (DORV) is a conotruncal defect in which both great arteries arise from the morphologic right ventricle, semilunar valves are not in fibrous continuity with either atrioventricular valve, and a ventricular septal defect (VSD) is commonly present (the only egress for blood to exit the left ventricle). The Society of Thoracic Surgeons (STS) Congenital Heart Surgery Nomenclature and Database Project Committee, the European Association of Cardiothoracic Surgery, and the European Association of Cardiologists have classified DORV into the following subtypes:


(1) VSD type (DORV with subaortic or doubly committed VSD without right ventricular outflow obstruction (RVOTO);


(2) Tetralogy of Fallot type (DORV with subaortic or doubly committed VSD with RVOTO);


(3) Transposition of the Great Arteries (TGA) type (DORV with subpulmonary VSD with or without RVOTO/Taussig-Bing Anomaly);


(4) Remote VSD type (DORV with uncommitted VSD with or without RVOTO);


(5) DORV and Atrioventricular septal defect.


Types 1 and 2 comprise approximately 65% of DORV while group 3 is present in approximately 25% of DORV. Group 4 and 5 make up the remainder of DORV. Associated defects seen with DORV include atrioventricular septal defects, aortic arch obstruction, ventricular hypoplasia, heterotaxy, mitral valve abnormalities, subaortic stenosis, pulmonary stenosis, and coronary artery anomalies. The position of a ventricular septal defect in relation to the great arteries and other associated anomalies determines the physiologic consequences of DORV, potential surgical repair, and dictates the appropriate anesthetic management.


In 1949, Taussig and Bing described a type of DORV with side-by-side position of the great arteries in which both great vessels arose from the right ventricle with supporting bilateral coni and a ventricular septal defect underlying both coni. The original definition has evolved over the years to include other variants of DORV with a subpulmonary VSD. In TGA type DORV/ Taussig-Bing Anomaly (TBA), the aorta may be located slightly anterior and rightward (d-transposition) or side-by-side with the pulmonary artery. Thus, the great vessels are parallel to each other and do not spiral around each other, as with normal anatomy. As a consequence of great vessel position and septal malalignment, there is preferential blood flow from the left ventricle through the VSD to the pulmonary artery and thus TGA physiology. TBA is also frequently associated with aortic arch obstruction, often resulting in discrete aortic coarctation, aortic arch hypoplasia or interrupted aortic arch.


Primary arterial switch operation (ASO) has become the first-line treatment for TBA without RVOTO. However, mortality is estimated to be 5-6%, which remains higher than the ASO for d-TGA. A study by Vergnat and colleagues reported a mortality rate of 5.8% in 69 patients with TBA. Most children who died in the immediate post-operative period or within the first postoperative year had an abnormal coronary pattern, specifically a looping or extended/prolonged course. Prolonged cardiopulmonary bypass (CPB) time was also a risk factor for mortality. These findings are like those reported in a 2023, single-institution study of 225 TBA patients by Gu et al. Overall 30-day mortality was 12.9%. Thirteen children died due to complications related to the coronary arteries (all within 48 hours after surgery). While intramural coronary anatomy did not reach statistical significance, it did tend to be a risk factor for mortality (adjusted OR 4.81, 95% CI 0.927-24.9, p = 0.062). In a sub-group analysis, a left circumflex artery originating from sinus two (Leiden convention) and looping behind the native pulmonary artery also tended to have a higher mortality. In normal coronary anatomy, the right coronary originates from sinus two and the left coronary artery originates from sinus one, eventually dividing into the left circumflex and left anterior descending coronary arteries. Prolonged CPB time was also noted to be a risk factor for mortality.


Reintervention remains common after the ASO in patients with DORV and TBA, with a reported incidence between 25 to 55% at 15 years. Most reinterventions are related to either RVOTO (neopulmonary) or left ventricular outflow tract obstruction (LVOTO). Right-sided reinterventions are mostly related to the subneopulmonary conus or pulmonary artery stenosis. On the left side, subneoaortic stenosis from muscular tissue, residual aortic arch obstruction and neo-aortic valve regurgitation are reported as the main reasons for reintervention. Several risk factors have been identified in the literature and seem to vary across studies for reintervention. These include aortic arch obstruction, preoperative subaortic RVOTO, side-by-side arteries and aortic to pulmonary artery (PA) size mismatch. Aortic arch obstruction may result in a higher pulmonary artery-to-aorta diameter ratio and a dilated neo-aortic root with a higher risk of neo-aortic insufficiency. However, neither side-by-side arteries, nor obstruction along the LVOT have been reported as risk factors for mortality in TBA patients.


REFERENCES


Mavroudis, C., Backer, C.L. and Anderson, R.H. . Double-Outlet Right Ventricle. In Mavroudis C, Backer CL. Eds. Pediatric Cardiac Surgery. 5th Edition. John Wiley & Sons Ltd. 2023. Pp. 499-537


Spaeth JP. Perioperative Management of DORV. Semin Cardiothorac Vasc Anesth. 2014;18(3):281-289. doi: 10.1177/1089253214528048


Vergnat M, Baruteau AE, Houyel L, et al. Late outcomes after arterial switch operation for Taussig-Bing anomaly. J Thorac Cardiovasc Surg. 2015;149(4):1124-1132. doi: 10.1016/j.jtcvs.2014.10.082


Fricke TA, Konstantinov IE. Arterial Switch Operation: Operative Approach and Outcomes. Ann Thorac Surg. 2019;107(1):302-310. doi: Fricke TA, Konstantinov IE. Arterial Switch Operation: Operative Approach and Outcomes. Ann Thorac Surg. 2019;107(1):302-310. doi: 10.1016/j.athoracsur.2018.06.002


Gu M, Hu J, Dong W, et al. Mid-Term Outcomes of Primary Arterial Switch Operation for Taussig-Bing Anomaly. Semin Thorac Cardiovasc Surg. 2023;35(3):562-571. doi: 10.1053/j.semtcvs.2022.06.001


Alsoufi A, Cai S, Williams WG, Coles JG et al. Improved results with single-stage total correction of Taussig-Bing Anomaly. Eur J Cardiothorac Surg. 2008;33(3) 244-250. doi: 10.1016/j.ejcts.2007.11.017