Truncus Arteriosus — Pathophysiology, Risks, and Management

Definition and Anatomy

Truncus arteriosus (common arterial trunk) is a conotruncal malformation in which a single arterial trunk arises from the heart and supplies the systemic, pulmonary, and coronary circulations, almost always in association with a large, nonrestrictive subtruncal VSD. The truncal valve is frequently dysplastic (often tricuspid or quadricuspid) with stenosis and/or regurgitation. Branch pulmonary arteries typically arise from the posterior or lateral aspect of the truncal root, and anatomic variants (Collett–Edwards and Van Praagh) inform operative strategy [1]. This lesion is strongly associated with 22q11.2 deletion (DiGeorge spectrum) [1].

Core Hemodynamics

Obligate mixing and L→R shunting. The large VSD permits streaming of left-sided output into the common trunk.

Pulmonary overcirculation. After birth, the physiologic fall in PVR drives excessive pulmonary blood flow, producing LV volume overload and pulmonary edema [1].

Diastolic runoff and low coronary perfusion pressure. Truncal valve regurgitation lowers aortic diastolic pressure; combined with elevated LVEDP from volume load, this compromises coronary perfusion and can precipitate ventricular dysfunction/ischemia.

Accelerated pulmonary vascular disease (if unrepaired). Sustained overcirculation leads to early pulmonary arteriopathy [1].

Key Risks (Why these patients decompensate)

1. Truncal valve regurgitation (TVR). TVR increases LV volume load (↑LVEDP) and depresses aortic diastolic pressure, threatening coronary flow; moderate–severe TVR is a recognized risk factor for mortality and reintervention [2, 7, 8].
2. Coronary anomalies. Aberrant origins/courses raise ischemic and surgical risk [2].
3. Interrupted aortic arch (IAA)/coarctation. Arch obstruction coexisting with truncus arteriosus magnifies afterload and diastolic runoff and is repeatedly linked to worse perioperative outcomes [2, 3].
4. Progressive pulmonary vascular disease in unrepaired or late-repaired cases due to chronic overcirculation [1].

Associated Findings

• IAA or coarctation in a substantial minority [3, 4].
• Truncal valve dysfunction (regurgitation ± stenosis) is common and often dictates timing/extent of repair [7, 8].
• Coronary artery anomalies (variable prevalence) require meticulous preoperative definition [2].
• 22q11.2 deletion/DiGeorge syndrome—consider genetic testing and related airway, immune, calcium, and vascular issues [1].

Clinical Presentation

Neonates typically present with tachypnea, feeding difficulty, failure to thrive, and signs of heart failure from pulmonary overcirculation; cyanosis may be mild and less conspicuous as PVR falls. A wide pulse pressure suggests significant diastolic runoff from TVR [1].

Diagnostic Work-Up

Echocardiography defines a single truncal root overriding a large VSD, evaluates truncal valve morphology/severity, delineates PA origins/size, and screens for arch obstruction. CT or cardiac MRI clarify complex PA, coronary, or arch anatomy when needed. Genetic testing for 22q11.2 is recommended [1].

Pre-operative Stabilization

Gentle diuresis to relieve pulmonary congestion; judicious afterload management (avoid excessive vasodilation when TVR is significant to preserve coronary perfusion); nutritional support; and prostaglandin E1 if arch obstruction or duct-dependent systemic flow is suspected.

Surgical Principles (Early Complete Repair is Standard)

Timing. Contemporary practice favors neonatal/early-infancy complete repair to prevent pulmonary vascular disease and improve survival [2, 5].

Goals of primary repair. (i) Patch closure of the VSD to route LV outflow exclusively to the truncal/aortic root (neo-aorta); (ii) separation of pulmonary circulation by detaching the PAs from the truncal root and establishing RV–PA continuity with a valved conduit/homograft (select centers may use non-conduit approaches in specific settings); (iii) truncal valve repair when regurgitation/stenosis is significant; and (iv) arch repair when IAA/CoA is present, with careful coronary protection throughout [2, 5].

Intra-/Post-operative targets. Maintain adequate systemic vascular resistance (to preserve diastolic coronary perfusion), avoid excessively high LVEDP (optimize preload/afterload and address residual TVR), and balance Qp:Qs to prevent recurrent pulmonary overcirculation.

Expected Reinterventions and Follow-Up

Conduits do not grow; RV–PA conduit replacement or catheter relief of obstruction is expected during childhood [3, 4, 6]. Truncal valve disease may progress, necessitating later repair or replacement; decisions are individualized based on severity, valve morphology, and ventricular impact [7, 8]. Branch PA stenosis or distortion may require surgical or transcatheter augmentation. Lifelong surveillance is essential.

Prognosis

With contemporary early repair, survival into adolescence and adulthood is favorable, but lifetime reintervention is common—especially for conduits and, when present, truncal valve disease. Outcomes are most influenced by (1) severity/reparability of TVR, (2) coronary anatomy, (3) branch PA caliber/anatomy, and (4) associated arch pathology and genetic comorbidities [3, 4, 6].

References

[1] Chikkabyrappa S, Mahadevaiah G, Buddhe S, Alsaied T, Tretter J. Common Arterial Trunk: Physiology, Imaging, and Management. Semin Cardiothorac Vasc Anesth. 2019;23(2):225-236.

[2] Hanley FL, Heinemann MK, Jonas RA, Mayer JE Jr, Cook NR, Wessel DL, Castaneda AR. Repair of truncus arteriosus in the neonate. J Thorac Cardiovasc Surg. 1993;105(6):1047-1056.

[3] Brown JW, Ruzmetov M, Okada Y, Vijay P, Turrentine MW. Truncus arteriosus repair: outcomes, risk factors, reoperation and management. Eur J Cardiothorac Surg. 2001;20(2):221-227.

[4] Tlaskal T, Chaloupecky V, Hucin B, Gebauer R, Krupickova S, Reich O, Skovranek J, Tax P. Long-term results after correction of persistent truncus arteriosus in 83 patients. Eur J Cardiothorac Surg. 2010;37(6):1278-1284.

[5] Thompson LD, McElhinney DB, Reddy VM, Petrossian E, Silverman NH, Hanley FL. Neonatal repair of truncus arteriosus: continuing improvement in outcomes. Ann Thorac Surg. 2001;72(2):391-395.

[6] Rajasinghe HA, McElhinney DB, Reddy VM, Mora BN, Hanley FL. Long-term follow-up of truncus arteriosus repaired in infancy: a twenty-year experience. J Thorac Cardiovasc Surg. 1997;113(5):869-878.

[7] Martínez-Quintana E, Portela-Torrón F. Truncus arteriosus and truncal valve regurgitation. Transl Pediatr. 2019;8(5):360-362.

[8] Bakar AM, Korsuize AM, d’Udekem Y, Naimo PS, et al. Multicenter Analysis of Truncal Valve Management and Outcomes in Children With Truncus Arteriosus. Ann Thorac Surg. 2020;110(4):1253-1261.