Tricuspid Atresia — Type II (Malposed/Transposed Great Arteries)

Date
September 20, 2025
URL
https://x.com/WithAScalpel/status/1969371425619251460
Categories
Tricuspid AtresiaSingle Ventricle

Tricuspid Atresia — Type II (Malposed/Transposed Great Arteries)

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Definition and segmental set

Tricuspid atresia (TA) is congenital absence of the right-atrium–to–right-ventricle (RA–RV) connection; systemic venous return must cross an interatrial communication to reach the left atrium (LA) and left ventricle (LV) [1]. In Type II TA, the great arteries are malposed—classically d-TGA—so the LV ejects to the pulmonary artery (PA) and the aorta (Ao) arises from a diminutive RV (ventriculo-arterial discordance) [2].

Anatomic substrate

  • Right heart. Atretic tricuspid valve with a hypoplastic RV composed largely of outlet tissue [1].
  • Interatrial level. An obligatory right-to-left shunt through a patent foramen ovale or atrial septal defect (ASD) permits systemic venous blood to enter the LV [1].
  • Ventricular level. A ventricular septal defect (VSD)—the bulboventricular foramen—is the sole route from LV to RV outflow/aorta; its caliber may decrease with muscular hypertrophy, creating progressive subaortic obstruction [2,3].
  • Outflow tracts. LV→PA and RV→Ao; diminished fetal antegrade Ao flow is associated with ascending aortic and arch hypoplasia (± coarctation) [2].

Core physiology

  1. ASD as the “inflow valve.” Adequate atrial shunting is essential for LV preload; restriction compromises pulmonary venous return and output [1].
  2. Systemic output set by the VSD/RVOT. The LV must drive systemic flow across the VSD into the RV outflow and Ao; restriction at the bulboventricular foramen and/or subaortic/RVOT produces systemic outflow obstruction [2,3].
  3. Pulmonary blood flow (PBF) set by subpulmonary obstruction. Unrestricted LV→PA flow causes pulmonary overcirculation and heart failure, whereas severe pulmonary stenosis/atresia yields ductal-dependent PBF with profound cyanosis [1,2].
  4. Ao hypoplasia. Low fetal Ao throughput predisposes to a small ascending aorta and arch; coarctation may coexist and worsen systemic afterload [2].

Type II subtypes (by pulmonary outflow)

  • IIa — Pulmonary atresia: PDA-dependent PBF; severe cyanosis [1].
  • IIb — Pulmonary stenosis: PBF varies with stenosis severity; phenotype ranges from cyanotic to balanced circulation [1].
  • IIc — No pulmonary stenosis: Excess PBF with tachypnea/poor feeding and failure to thrive from pulmonary overcirculation [2].

Clinical presentation

Cyanosis is universal (greatest in IIa/IIb); signs of heart failure dominate in IIc. A single, loud S2 is typical; murmurs reflect VSD/RVOT or pulmonary outflow lesions. Differential upper–lower saturation is unusual unless arch obstruction is present [1,2].

Diagnostic evaluation

  • Echocardiography delineates atrioventricular discontinuity, VSD size/location, great-artery relationships, RVOT and pulmonary valve status, and arch dimensions [1].
  • Oximetry and blood gases profile Qp:Qs balance and guide early titration of oxygen/ventilation [2].
  • Cross-sectional imaging/catheterization is reserved for unresolved questions (arch/coarctation, coronary origins, or quantification of VSD/RVOT gradients) [2,3].

Initial stabilization

  • Prostaglandin E1 (PGE1) when either circulation is ductal-assisted:

    • – Low PBF (IIa/critical IIb): maintain ductal patency to supply the lungs.

    – Compromised systemic output from a restrictive VSD/subaortic narrowing or significant arch hypoplasia: maintain ductal Ao flow while planning definitive relief [1,2].

  • Oxygen/ventilation are titrated to avoid exacerbating pulmonary overcirculation in IIc; diuretics treat heart-failure symptoms [2].
  • Early attention to coarctation/arch hypoplasia is critical to protect systemic output and cerebral perfusion [3].

Operative strategy (single-ventricle pathway)

Goal: achieve balanced Qp:Qs in the neonatal period, then stage cavopulmonary connections toward Fontan completion.

Neonatal stage (individualized to PBF and systemic pathway)

  • Low PBF (IIa/IIb). A modified Blalock–Taussig shunt (mBTS) provides controlled PBF and reliable oxygenation in neonates [4,5,7].
  • Excess PBF (IIc). Pulmonary artery banding (PAB) protects the pulmonary vascular bed and stabilizes symptoms; absorbable materials may permit spontaneous “de-banding” as VSDs become restrictive [6,8].
  • Systemic outflow obstruction. When the bulboventricular foramen becomes restrictive and/or the subaortic pathway is narrow, options include VSD enlargement or a Damus–Kaye–Stansel (DKS) connection (often with arch augmentation) to secure an unobstructed neo-aortic pathway from the LV [2,3].

Superior cavopulmonary connection — Bidirectional Glenn/Hemifontan (≈3–6 months)

Performed once PVR has fallen and pulmonary arteries are adequate; concomitant relief of any residual systemic outflow obstruction (VSD enlargement or DKS) is undertaken if not solved in the neonatal stage [2,3].

Fontan completion (≈2–4 years)

Extracardiac conduit or lateral tunnel—often with a selective fenestration—when pulmonary arteries are well-developed, PVR is low, ventricular function is satisfactory, and AV-valve regurgitation is minimal [1,2].

Recurrent issues and longitudinal surveillance

  • Progressive subaortic (bulboventricular foramen) obstruction: requires serial echocardiography; timely VSD enlargement or DKS before/at Glenn improves downstream outcomes [2,3].
  • Aortic arch hypoplasia/coarctation: treat when gradients or afterload rise [3].
  • AV-valve competence (mitral): preserve to maintain Fontan candidacy [1,2].
  • Thromboembolism/arrhythmias: follow standard single-ventricle surveillance and antithrombotic strategies as indicated [2].
  • Expected outcomes. With contemporary staged management, survival into later childhood and adolescence is high; recent series report ≈80–90% medium-term survival following staged palliation for TA cohorts, consistent with multi-institutional experience [3,9,10].

Clinical pearl

In Type II TA, think of three controllable “valves”: the ASD (inflow), the bulboventricular foramen/subaortic pathway (systemic outflow), and the pulmonary valve/subpulmonary tract (Qp). Neonatal therapy targets these determinants to balance Qp:Qs and prepare the child for Glenn and Fontan [1–3].

References

[1] Rao PS. Tricuspid atresia. Clin Cardiol. 2000;23(5):311–319.

[2] Sumal AS, Gowda S, Bansal A, Hoschtitzky A. Tricuspid atresia: Where are we now? J Card Surg. 2020;35(11):2864–2874.

[3] Alsoufi B, Mahle WT, Schlosser B, et al. Influence of morphology and initial surgical strategy on survival of infants with tricuspid atresia. Ann Thorac Surg. 2015;100(4):1403–1409.

[4] Ilbawi MN, Idriss FS, DeLeon SY, et al. Modified Blalock–Taussig shunt in newborn infants. J Thorac Cardiovasc Surg. 1984;88(5 Pt 1):770–775.

[5] Kiran U, Aggarwal S, Makhija N, Chowdhury UK. The Blalock and Taussig shunt revisited. Ann Card Anaesth. 2017;20(3):323–330.

[6] Tingelstad JB, Feldt RH, Kirchhoff PG, McGoon DC. Pulmonary artery banding in tricuspid atresia without transposed great arteries. Am J Dis Child. 1971;121(5):434–437.

[7] O’Connor MJ, Ravishankar C, Ballweg JA, et al. Early systemic-to-pulmonary artery shunt intervention in neonates: analysis of shunt size and outcomes. J Thorac Cardiovasc Surg. 2011;142(2):336–342.

[8] Bonnet D, Sidi D, Kachaner J, et al. Absorbable pulmonary artery banding in tricuspid atresia. Ann Thorac Surg. 2001;71(2):740–742.

[9] Karamlou T, Silber I, Lao R, et al. Matching procedure to morphology improves outcomes in tricuspid atresia with ventriculoarterial concordance. Ann Thorac Surg. 2005;80(2):642–648.

[10] Dalén M, Dellborg M, Eriksson P, et al. Long-term survival after single-ventricle palliation: a nationwide cohort study. J Am Heart Assoc. 2024;13(9):e031030.