Pulmonary Artery Banding (PAB) #3: PAB in the Single-Ventricle Pathway

1. Core Concept

In single-ventricle physiology, pulmonary artery banding is fundamentally a flow-balancing operation. Its purpose is not simply to lower pulmonary artery pressure, but to restrict excessive pulmonary blood flow (Qp), preserve effective systemic blood flow (Qs), reduce ventricular volume loading, and protect the pulmonary vascular bed for subsequent cavopulmonary palliation [1].

Because both pulmonary and systemic circulations are supplied by the same functional ventricle, total ventricular output can be conceptualized as:

Single-ventricle output = Qp + Qs

When pulmonary vascular resistance falls after birth and pulmonary blood flow is unrestricted, a disproportionate fraction of ventricular output may be directed toward the pulmonary circulation. Systemic arterial oxygen saturation may consequently be relatively high, but systemic perfusion can still be inadequate because excessive cardiac output is being recirculated through the lungs rather than delivered to the systemic circulation.

PAB introduces a controlled resistance into the pulmonary pathway. The objective is therefore to create a balanced parallel circulation, accepting moderate systemic desaturation when necessary in exchange for improved systemic perfusion, reduced ventricular workload, and lower pulmonary vascular pressure and flow.

2. Why Pulmonary Overcirculation Is Harmful

In a circulation with complete or near-complete mixing, pulmonary and systemic vascular beds compete for the output of one functional ventricle. The distribution of flow is strongly influenced by the relative resistances of the two circulations.

As pulmonary vascular resistance normally falls during the neonatal period, unrestricted pulmonary blood flow may increase substantially.

Excessive Qp

Pulmonary overcirculation may produce:

• Tachypnea and increased work of breathing
• Pulmonary congestion or edema
• Feeding difficulty and poor growth
• Cardiomegaly
• Relatively high systemic oxygen saturation
• Low systemic diastolic pressure
• Reduced systemic perfusion reserve
• Metabolic acidosis when systemic output becomes inadequate

Importantly, a saturation in the 90% range is not necessarily desirable in parallel single-ventricle physiology. It may indicate excessive Qp rather than optimal systemic oxygen delivery.

Ventricular Volume Overload

Pulmonary blood flow returns through the pulmonary veins and ultimately re-enters the single ventricle. Excessive Qp therefore produces excessive ventricular preload.

The ventricle must generate both effective systemic blood flow and the large volume of blood repeatedly recirculating through the lungs. Chronic volume loading can contribute to ventricular dilation, increased filling pressures, atrioventricular valve regurgitation, and progressive ventricular dysfunction.

Evidence supporting this physiologic rationale is available from conventional PAB cohorts. Kajihara and colleagues compared two eras of PAB in 68 patients with functionally single ventricles and unrestricted pulmonary blood flow. A strategy of tighter neonatal PAB followed by earlier bidirectional cavopulmonary shunting was associated with lower pre-Glenn ventricular end-diastolic volume—166% versus 212% of normal—and lower pulmonary resistance index—1.9 versus 2.4 U·m² [2].

3. Protection of the Pulmonary Vascular Bed

Preservation of low pulmonary vascular resistance is particularly important because the ultimate single-ventricle pathway depends on passive cavopulmonary blood flow.

After the bidirectional Glenn procedure, superior vena caval blood flows directly into the pulmonary arteries without a subpulmonary ventricular pump. After Fontan completion, essentially the entire systemic venous return must pass through the pulmonary vascular bed using a relatively small pressure gradient.

A pulmonary circulation exposed early to prolonged excessive flow and pressure may therefore become less favorable for later cavopulmonary physiology.

The conventional rationale for PAB is to reduce pulmonary flow and distal pulmonary artery pressure before irreversible pulmonary vascular remodeling develops [1]. However, direct evidence demonstrating that PAB quantitatively improves long-term pulmonary vascular development remains limited. Available studies more commonly use pulmonary artery pressure, pulmonary vascular resistance, pulmonary artery size, Glenn eligibility, and later Fontan progression as indirect markers.

Thus, PAB should be understood as a strategy intended to preserve a low-resistance pulmonary vascular bed, although the magnitude of its long-term effect on pulmonary vascular remodeling has not been precisely defined.

4. Physiologic Effect of PAB

Before banding:

Low pulmonary resistance → excessive Qp → increased pulmonary venous return → ventricular volume overload → reduced systemic perfusion reserve

After appropriately adjusted banding:

Controlled pulmonary resistance → reduced Qp → improved effective Qs → reduced ventricular preload → lower pulmonary pressure and flow

The purpose is not maximal restriction. Pulmonary flow must remain sufficient for adequate systemic oxygenation.

A useful conceptual endpoint is therefore balanced circulation, in which pulmonary and systemic flows are appropriately matched for the anatomy and stage of palliation.

Conventional guidance has suggested a distal pulmonary artery pressure of approximately 30–50% of systemic pressure in biventricular physiology. In a univentricular circulation, substantially lower pulmonary pressure is desirable, with an idealized target approaching pressures ultimately compatible with Fontan physiology, approximately a mean of 15 mmHg [1]. These values should be interpreted as physiologic guides rather than universal operative thresholds.

5. Qp/Qs Balance: Why Lower Saturation Can Be Better

The central concept is redistribution of a finite ventricular output between Qp and Qs.

An infant with unrestricted pulmonary flow and systemic saturation of 92% may appear well oxygenated, yet a large proportion of total ventricular output may be recirculating through the lungs. Effective systemic output may remain inadequate.

After PAB, saturation may decrease to approximately 75–85%, while systemic blood pressure, urine output, lactate, cerebral and somatic perfusion, and ventricular loading improve.

Therefore:

Higher saturation does not necessarily mean better circulation.

The objective is adequate systemic oxygen delivery, not normalization of arterial oxygen saturation.

This principle has important postoperative implications. Excessive oxygen administration, hyperventilation, respiratory alkalosis, or other interventions that markedly reduce pulmonary vascular resistance may increase Qp and undermine the intended physiologic effect of the band.

6. How Tight Should a Conventional PAB Be?

No single gradient, pressure, or saturation defines successful PAB in every single-ventricle patient.

Ergün and colleagues studied 50 consecutive patients with single-ventricle anatomy and unrestricted pulmonary blood flow after PAB. Thirty-four patients progressed successfully toward Glenn/Fontan physiology, whereas 16 failed to progress. Lower pulmonary arterial pressure after banding was associated with successful progression. The median predischarge band gradient was approximately 60 mmHg in the successful group compared with 47.5 mmHg in the failure-to-progress group [3].

Similarly, the tighter-band strategy reported by Kajihara and colleagues was associated not only with reduced ventricular volume and lower pulmonary resistance, but also with markedly greater achievement of right-heart bypass by 12 months: 81% compared with 19% in the earlier treatment era [2].

These observations support sufficiently restrictive banding, but they do not establish a universal numerical target.

Band adjustment should integrate:

• Systemic arterial oxygen saturation
• Distal pulmonary artery pressure
• Systemic arterial pressure
• Ventricular function
• Atrioventricular valve regurgitation
• Systemic perfusion
• Lactate and acid-base status
• Cerebral and somatic near-infrared spectroscopy when available
• Pulmonary artery anatomy
• Anticipated next stage of palliation

A band that is too loose leaves persistent pulmonary overcirculation and ventricular volume loading. A band that is too tight can cause severe hypoxemia, inadequate pulmonary flow, and compromised oxygen delivery.

7. Conventional Main PAB in the Single-Ventricle Pathway

Conventional main PAB is most applicable when excessive antegrade pulmonary blood flow originates from the functional ventricle and systemic output does not depend on flow through the proximal pulmonary artery.

Potential settings include:

• Tricuspid atresia with unrestricted pulmonary blood flow
• Double-inlet left ventricle
• Unbalanced atrioventricular septal defect committed to single-ventricle palliation
• Selected double-outlet right ventricle anatomies
• Heterotaxy with functional single-ventricle physiology
• Single-ventricle lesions combined with selected forms of systemic outflow or arch obstruction

Contemporary results demonstrate that this remains a viable strategy in selected patients. In a cohort of 73 patients with single-ventricle anomalies and unrestricted pulmonary flow, including 29 undergoing simultaneous arch repair, hospital mortality after initial PAB was 4%. At 2 years, 88% had undergone Glenn palliation, and overall 5-year survival after PAB was 86% [4].

These findings also demonstrate that PAB can be incorporated into a broader staged reconstruction strategy when systemic outflow or arch anatomy requires simultaneous treatment.

8. Bilateral PAB Is a Distinct Strategy

Bilateral pulmonary artery banding must be distinguished from conventional main PAB.

This distinction is particularly important in hypoplastic left heart syndrome (HLHS) and other ductal-dependent systemic circulations.

In HLHS, right ventricular output enters the pulmonary artery and supplies both pulmonary and systemic circulations. Systemic blood flow reaches the aorta through the patent ductus arteriosus. A conventional main PAB would therefore obstruct not only pulmonary flow but also the pathway required for systemic output.

Instead, the right and left branch pulmonary arteries are individually banded.

The fundamental objective becomes:

Restrict Qp while preserving ductal Qs.

Bilateral PAB can therefore:

• Restrict pulmonary overcirculation
• Preserve systemic output through the ductus
• Reduce pulmonary venous return and ventricular volume loading
• Stabilize systemic perfusion
• Provide time before definitive or second-stage reconstruction

This strategy forms the pulmonary-flow-control component of hybrid palliation, combined with maintenance of ductal patency and an adequate atrial communication.

9. Achieving Balance With Bilateral PAB

Bilateral PAB is technically sensitive because both pulmonary arteries must be restricted sufficiently and relatively symmetrically.

In a 44-neonate series of hybrid bilateral PAB, Suvorov and colleagues compared different intraoperative methods of band adjustment. Overall, a Qp/Qs ratio of approximately 1:1 was achieved in 30 of 44 patients. With the technique incorporating intraoperative assessment of flow characteristics at the banding sites, the target balance was achieved in 21 of 22 patients, or 95.5% [5].

These data reinforce the concept that bilateral PAB should not be viewed merely as placement of two fixed bands. It is an intraoperative hemodynamic calibration procedure.

In HLHS or other ductal-dependent systemic circulation, adequate systemic output additionally requires:

• Unobstructed ductal flow
• Adequate atrial-level decompression
• Preserved right ventricular function
• Acceptable tricuspid valve function
• Symmetric and adequate branch pulmonary artery perfusion

Failure of any component can destabilize the circulation even if the bands themselves are technically satisfactory.

10. Bilateral PAB as Stabilization or Rescue

Bilateral PAB may be particularly valuable when conventional neonatal reconstruction carries excessive immediate risk.

Reported applications include:

• High-risk or unstable HLHS
• Cardiogenic shock
• Low birth weight or prematurity
• Severe extracardiac disease
• Complex arch obstruction
• Borderline ventricular anatomy in which the ultimate pathway remains uncertain

In a series of 66 bilateral-PAB procedures involving complex congenital heart disease, 10 patients underwent banding as rescue therapy for shock, and 8 recovered sufficiently to proceed with further management [6].

Similarly, Guleserian and colleagues reported bilateral PAB with ductal stenting or prostaglandin-dependent ductal maintenance in 24 high-risk single-ventricle infants considered poor candidates for conventional initial palliation. Fifteen patients, or 62.5%, survived to subsequent Norwood reconstruction, comprehensive stage II palliation, or transplantation [7].

Thus, bilateral PAB can function not only as planned hybrid palliation but also as a resuscitative bridge, allowing physiologic recovery before a more extensive operation.

11. Complications and Need for Reintervention

Neither conventional nor bilateral PAB is a benign procedure.

Potential complications include:

• Inadequate restriction and persistent pulmonary overcirculation
• Excessive restriction and severe cyanosis
• Band migration
• Pulmonary artery distortion
• Branch pulmonary artery stenosis
• Unequal right-versus-left pulmonary blood flow after bilateral PAB
• Ductal obstruction in ductal-dependent systemic circulation
• Ventricular dysfunction
• Progressive atrioventricular valve regurgitation
• Need for band adjustment or reconstruction

In the 73-patient conventional PAB series, 16 patients—22%—required 18 operations before Glenn palliation, including shunt placement, Damus–Kaye–Stansel procedures, and PAB adjustment [4].

In the 66-patient bilateral-PAB series, 13 patients—20%—required repeat band surgery, most commonly loosening of an excessively restrictive band, and 11% developed ductal obstruction while awaiting the next stage [6].

These findings emphasize the need for close surveillance. PAB is not a static intervention; somatic growth, falling pulmonary vascular resistance, ductal physiology, and evolving ventricular function can alter the balance achieved at the initial operation.

12. Preparation for Glenn and Fontan Palliation

The ultimate value of PAB is determined by whether it establishes a circulation favorable for subsequent cavopulmonary connection.

In Kajihara's tighter-band era, improved hemodynamics before bidirectional cavopulmonary shunting were accompanied by substantially greater early progression to right-heart bypass [2]. In the larger contemporary cohort reported by Alsoufi and colleagues, 88% had reached Glenn palliation by 2 years. Among patients reaching Glenn, 71% had subsequently undergone Fontan completion by 5 years [4].

However, outcomes depend on more than pulmonary flow restriction. After bilateral PAB, postoperative atrioventricular valve regurgitation, impaired ventricular function, and elevated pulmonary venous wedge pressure have been associated with mortality before bidirectional Glenn palliation [8].

Therefore, successful PAB should be evaluated as part of the entire single-ventricle substrate:

• Pulmonary vascular resistance
• Pulmonary artery architecture
• Ventricular systolic and diastolic function
• Atrioventricular valve competence
• Systemic outflow
• Pulmonary venous pressure
• Systemic oxygen delivery

The procedure creates favorable conditions for the next stage, but it cannot compensate for all adverse features of the underlying anatomy.

13. Surgical and Physiologic Perspective

The fundamental principle of PAB in single-ventricle physiology is:

The goal is not the highest possible oxygen saturation; the goal is the most effective distribution of a limited single-ventricle output.

A successful band converts uncontrolled pulmonary overcirculation into controlled pulmonary blood flow. This reduces pulmonary venous recirculation, decreases ventricular volume loading, preserves systemic perfusion reserve, and seeks to maintain a low-pressure pulmonary vascular bed suitable for later Glenn and Fontan physiology.

Conventional main PAB is primarily used when antegrade pulmonary blood flow is excessive and systemic output does not depend on the proximal pulmonary artery.

Bilateral PAB is fundamentally different and is particularly applicable when the proximal pulmonary artery must remain part of the systemic output pathway, as in HLHS and related ductal-dependent circulations.

The evidence consistently supports the physiologic importance of adequate restriction, but contemporary data remain predominantly retrospective and heterogeneous. No universally validated pressure, gradient, saturation, or Qp/Qs target exists, and direct evidence concerning long-term pulmonary vascular development remains limited.

PAB should therefore be understood not as a procedure defined by a particular band circumference or pressure gradient, but as a deliberate manipulation of Qp/Qs balance, systemic oxygen delivery, ventricular workload, pulmonary vascular loading, and future cavopulmonary physiology.

References

[1] Sharma R. Pulmonary artery banding: Rationale and possible indications in the current era. Ann Pediatr Cardiol. 2012;5(1):40-43. (PubMed Central (PMC))

[2] Kajihara N, Asou T, Takeda Y, Kosaka Y, Onakatomi Y, Nagafuchi H, Yasui S. Pulmonary artery banding for functionally single ventricles: impact of tighter banding in staged Fontan era. Ann Thorac Surg. 2010;89(1):174-179. (PubMed)

[3] Ergün S, Çilsal E, Genç SB, Yıldız O, Tanıdır İC, Onan İS, Güzeltaş A, Haydin S. Univentricular pulmonary artery banding: how tight is tight enough for successful progress? Pediatr Cardiol. 2021;42(4):840-848. (PubMed)

[4] Alsoufi B, Manlhiot C, Ehrlich A, Oster M, Kogon B, Mahle WT, Maher K, McCrindle BW, Kanter K. Results of palliation with an initial pulmonary artery band in patients with single ventricle associated with unrestricted pulmonary blood flow. J Thorac Cardiovasc Surg. 2015;149(1):213-220. (PubMed)

[5] Suvorov V, Zaitcev V, Andrzejczyk K. Effectiveness of bilateral pulmonary artery banding in patients with hypoplastic left heart syndrome and congenital heart defects with a functional single ventricle: a single-center retrospective study. Congenit Heart Dis. 2022;17(3):365-374. (TechScience)

[6] Sakurai T, Sakurai H, Yamana K, Nonaka T, Noda R, Otsuka R, Osawa T. Expectations and limitations after bilateral pulmonary artery banding. Eur J Cardiothorac Surg. 2016;50(4):626-631. (OUP Academic)

[7] Guleserian KJ, Barker GM, Sharma MS, Macaluso J, Huang R, Nugent AW, Forbess JM. Bilateral pulmonary artery banding for resuscitation in high-risk, single-ventricle neonates and infants: a single-center experience. J Thorac Cardiovasc Surg. 2013;145(1):206-214. (PubMed)

[8] Ishii Y, Inamura N, Kayatani F, Iwai S, Kawata H, Arakawa H, Kishimoto H. Evaluation of bilateral pulmonary artery banding for initial palliation in single-ventricle neonates and infants: risk factors for mortality before the bidirectional Glenn procedure. Interact Cardiovasc Thorac Surg. 2014;19(5):807-811. (OUP Academic)