Bidirectional Glenn (Cavopulmonary Anastomosis)

Purpose and physiologic intent

The bidirectional Glenn (BDG) routes superior vena cava (SVC) return directly to the branch pulmonary arteries (PAs), thereby removing SVC-related volume work from the single ventricle and providing steady, nonpulsatile pulmonary blood flow (PBF). Staging with BDG lowers ventricular end-diastolic volume, improves ventriculoarterial coupling, and optimizes energetic efficiency for the subsequent total cavopulmonary connection (TCPC/Fontan) [1]. Historically introduced to make “high-risk” patients better Fontan candidates, BDG is now broadly used as the standard stage-II palliation in most single-ventricle pathways [2, 4].

Patient selection and prerequisites

• Anatomy. Unobstructed, adequately sized branch PAs; an SVC of sufficient length without stenosis; and absence of large systemic-to-pulmonary venous collaterals that could elevate post-BDG venous pressure.
• Hemodynamics. Programs commonly target low pulmonary vascular resistance (PVR index ≤2–3 WU·m²) and a mean PA pressure in the low-teens; higher PVR is consistently associated with worse outcomes after BDG and diminished progression to Fontan (e.g., PVRi > 3 WU·m² increased mortality in multivariable analyses) [3]. Elevated mean PA pressure has repeatedly emerged as an adverse predictor for stage-II and stage-III outcomes [2, 4].
• Rhythm/conduction. Sinus rhythm is preferred; protect the sinoatrial (SA) node and its arterial supply during SVC–RA separation.
• Antegrade PBF. If native MPA flow, a systemic-to-pulmonary shunt, or an RV–PA conduit is present, most centers restrict or eliminate antegrade PBF at BDG to avoid overcirculation; evidence on intentional residual antegrade flow is mixed (see “Variations”) [7, 8].

Operative setup and cannulation

BDG is commonly performed on cardiopulmonary bypass (CPB) to facilitate a dry field and cerebral protection during SVC clamping. Typical cannulation: aortic arterial cannula; venous drainage via the right atrium (or IVC) plus high SVC cannulation to decompress the head and neck during SVC division; ligate the azygos vein to prevent SVC “bypass.” Off-pump BDG with temporary veno-venous shunting is feasible in selected patients and yields comparable early and mid-term outcomes to on-pump strategies [6].

Eliminate antegrade pulmonary flow (as indicated)

To prevent excessive PBF and V/Q mismatch, divide or oversew the main pulmonary artery (MPA) and takedown any shunts or RV–PA conduits that would otherwise deliver uncontrolled antegrade flow. Some programs purposefully retain a limited trickle; contemporary series suggest that, when used judiciously, additional antegrade PBF does not worsen early outcomes and may raise saturations (see below) [7, 8].

SVC–RA separation (protecting the SA node)

Divide the SVC–RA junction and oversew the right atrial stump, taking care to remain posterior–superior to the sulcus terminalis to avoid SA-node injury and preserve sinus rhythm.

Preparing the pulmonary artery recipient site

Snare the branch PAs. Create a longitudinal arteriotomy on the right PA (RPA) aligned with the inflow vector from the SVC to enable an in-plane, tension-free end-to-side anastomosis. Perform patch plasty if the RPA is small or crowded to ensure a wide, non-constricting hood and minimize shear-related stenosis.

The cavopulmonary anastomosis

Construct an end-to-side SVC–RPA anastomosis with continuous monofilament suture.

• Geometry. Maintain a gentle SVC curve without torsion; avoid kinks at the heel.
• Caliber match. If SVC and RPA sizes differ, lengthen the arteriotomy (heel-to-toe) or add a small hood patch rather than “snugging down” the SVC—avoid purse-string narrowing that produces fixed stenosis and pressure gradients.
• De-airing. Allow controlled back-bleeding and irrigate before closing the anterior wall.

Reperfusion and assessment

Release snares sequentially—PA first, then SVC—to re-establish Glenn flow smoothly. Confirm:

• SVC–PA gradient. Expect a low or negligible step-up; a significant gradient suggests anastomotic narrowing, distal PA obstruction, or high collateral return.
• Systemic venous pressure. “Glenn pressure” typically settles in the low- to mid-teens with adequate ventilation and normothermia.
• Oxygenation. Saturations in the mid- to high-80s are typical early after BDG.

Separation from bypass and immediate management

Wean with strategies that lower PVR: lung recruitment, avoidance of atelectasis, normocapnia or mild hypocapnia, and judicious FiO₂; these principles reflect the preload-limited nature of cavopulmonary physiology [9]. Maintain adequate preload, sinus rhythm, and use only gentle inotropes if needed—excess tachycardia shortens diastole and impairs passive venous return. Before closure, reconfirm a stable Glenn pressure, satisfactory saturations, and absence of a technical gradient.

Variations and special scenarios

• Off-pump BDG. Comparable early morbidity, length of stay, and survival to on-pump BDG in appropriately selected patients [6].
• Bilateral/left-sided Glenn. A persistent left SVC is common; unilateral vs bilateral BDG shows no adverse difference in outcomes, and cannulation strategy or presence of antegrade PBF were not independent risk factors in large series [5].
• Hemi-Fontan vs BDG. Both provide superior cavopulmonary connection; choice is center-specific. Large single-center BDG series support excellent staged outcomes across morphologies when PA pressure is controlled [4].
• Antegrade PBF at BDG. Evidence is mixed: early data indicate no detrimental effect on composite outcomes [7], and some cohorts report higher postoperative saturations and a longer interval to TCPC—potentially permitting PA growth and a larger extracardiac conduit at Fontan [8]. Programs should balance these benefits against the risks of SVC hypertension and overcirculation.

Pitfalls and how to avoid them

1. Anastomotic stenosis. Use a generous arteriotomy/patch and precise heel–toe geometry; re-check for a gradient before leaving the OR.
2. Tension/torsion on SVC. Mobilize adequately; ensure a natural lie to avoid SVC syndrome.
3. PA hypoplasia. Patch-enlarge small RPA segments upfront to prevent high Glenn pressures and protect cerebral venous outflow.
4. Persisting antegrade PBF. Residual shunts can drive overcirculation and ventricular volume loading—eliminate them when classic BDG physiology is intended, or document a deliberate “trickle” strategy with tight surveillance [7, 8].
5. Hemodynamic risk factors. Elevated central venous pressure (CVP) and transpulmonary gradient, prolonged CPB time, and right-ventricular morphology correlate with longer drainage, prolonged stay, and complications [5]. Higher pre-operative PA pressures are linked to more inotrope use and longer ventilation [10].

Early postoperative priorities

• Ventilation strategy. Prevent atelectasis, avoid hypercarbia and acidosis, and use gentle PEEP to keep PVR low [9].
• Volume and rhythm. Maintain euvolemia; treat junctional rhythms promptly if they compromise passive flow.
• Surveillance. Track Glenn pressure trends, head/neck edema, and oxygenation. A new SVC–PA gradient or rising venous pressure warrants early imaging and consideration of catheter intervention.
• Programmatic outcomes. Contemporary multi-institution and single-center series confirm good survival to Fontan but emphasize ongoing attrition; careful attention to PVR, PA pressure, and perioperative factors remains key [3–5, 10].

References

[1] Tanoue Y, Sese A, Ueno Y, Joh K, Hijii T. Bidirectional Glenn procedure improves the mechanical efficiency of a total cavopulmonary connection in high-risk Fontan candidates. Circulation. 2001;103(17):2176-2180.

[2] Bridges ND, Jonas RA, Mayer JE, Flanagan MF, Keane JF, Castaneda AR. Bidirectional cavopulmonary anastomosis as interim palliation for high-risk Fontan candidates. Early results. Circulation. 1990;82(5 Suppl):IV170-IV176.

[3] Alsoufi B, Manlhiot C, Awan A, Alfadley F, Al-Ahmadi M, Al-Wadei A, McCrindle BW, Al-Halees Z. Current outcomes of the Glenn bidirectional cavopulmonary connection for single ventricle palliation. Eur J Cardiothorac Surg. 2012;42(1):42-48.

[4] Tanoue Y, Kado H, Boku N, Tatewaki H, Nakano T, Fukae K, Masuda M, Tominaga R. Three hundred and thirty-three experiences with the bidirectional Glenn procedure in a single institute. Interact Cardiovasc Thorac Surg. 2007;6(1):97-101.

[5] Kogon BE, Plattner C, Leong T, Simsic J, Kirshbom PM, Kanter KR. The bidirectional Glenn operation: a risk factor analysis for morbidity and mortality. J Thorac Cardiovasc Surg. 2008;136(5):1237-1242.

[6] LaPar DJ, Mery CM, Peeler BB, Kron IL, Gangemi JJ. Short and long-term outcomes for bidirectional Glenn procedure performed with and without cardiopulmonary bypass. Ann Thorac Surg. 2012;94(1):164-170.

[7] Berdat PA, Belli E, Lacour-Gayet F, Planché C, Serraf A. Additional pulmonary blood flow has no adverse effect on outcome after bidirectional cavopulmonary anastomosis. Ann Thorac Surg. 2005;79(1):29-36.

[8] van Slooten YJ, Elzenga NJ, Waterbolk TW, van Melle JP, Berger RMF, Ebels T. The effect of additional pulmonary blood flow on timing of the total cavopulmonary connection. Ann Thorac Surg. 2012;93(6):2028-2033.

[9] Gewillig M, Brown SC, Eyskens B, Heying R, Ganame J, Budts W, La Gerche A, Gorenflo M. The Fontan circulation: who controls cardiac output? Interact Cardiovasc Thorac Surg. 2010;10(3):428-433.

[10] François K, De Groote K, Vandekerckhove K, De Wilde H, Van Nooten G, et al. Current outcomes of the bi-directional cavopulmonary anastomosis in single ventricle patients: analysis of risk factors for morbidity and mortality, and suitability for Fontan completion. Cardiol Young. 2016;26(2):288-297.