Pulmonary Artery Banding

Updated: Nov 30, 2022
Author: Shabir Bhimji, MD, PhD; Chief Editor: Suvro S Sett, MD, FRCSC, FACS 

Overview

Background

Pulmonary artery banding (PAB) is a technique of palliative surgical therapy used by congenital heart surgeons as a staged approach for operative correction of congenital heart defects. This technique was widely used in the past as an initial surgical intervention for infants born with cardiac defects characterized by left-to-right shunting and pulmonary overcirculation. Within the last two decades, early definitive intracardiac repair has largely replaced palliation with PAB. This trend has evolved because many centers have demonstrated improved outcomes with primary corrective surgery as an initial intervention in the neonate with congenital heart disease. Although the use of PAB has significantly decreased, it continues to maintain a therapeutic role in certain subsets of patients with congenital heart disease.

The primary objective of performing PAB is to reduce excessive pulmonary blood flow and protect the pulmonary vasculature from hypertrophy and irreversible (fixed) pulmonary hypertension. More recently, PAB has played a role in the preparation and "training" of the left ventricle (LV) in patients with dextro-transposition of the great arteries (d-TGA) who are evaluated for a delayed arterial switch procedure. It has found a similar role in training the LV in patients with levo-transposition of the great arteries (L-TGA) who may also be candidates for an arterial switch procedure.

Pulmonary Artery Banding. Safe placement of a pulm Pulmonary Artery Banding. Safe placement of a pulmonary artery band: (A) encircling the aortopulmonary trunk, (B) encircling the aorta, and (C) completing the pulmonary artery band at the final location.

History of the Procedure

The first description of pulmonary artery banding (PAB) in the literature was a report by Muller and Danimann at the University of California, Los Angeles (UCLA) in 1951.[1] In this report, Muller and Danimann described palliation by the "creation of pulmonary stenosis" in a 5-month-old infant who had a large ventricular septal defect (VSD) and pulmonary overcirculation. Following this report, multiple studies were published demonstrating the effectiveness of this technique in infants with congestive heart failure caused by large VSDs, complex lesions (eg, atrioventricular canal defects), and tricuspid atresia.[2, 3, 4, 5, 6, 7, 8, 9, 10, 11]

Although the use of PAB has declined, it remains an essential technique for comprehensive surgical treatment in patients with congenital heart disease. PAB is a palliative but not a curative surgical procedure.

Pathophysiology

Congenital heart defects with left-to-right shunting and unrestricted pulmonary blood flow (PBF) due to a drop in pulmonary vascular resistance result in pulmonary overcirculation. In the acute setting, this leads to pulmonary edema and congestive heart failure in the neonate. Within the first year of life, this unrestricted flow and pressure can lead to medial hypertrophy of the pulmonary arterioles and fixed pulmonary hypertension. Pulmonary artery banding (PAB) creates a narrowing, or stenosing, of the main pulmonary artery that decreases blood flow to the branch pulmonary arteries and reduces PBF and pulmonary artery pressure. In patients with cardiac defects that produce left-to-right shunting, this restriction of PBF reduces the shunt volume and consequently improves both systemic pressure and cardiac output. A reduction of PBF also decreases the total blood volume returning to the LV (or the systemic ventricle) and often improves ventricular function.

PAB may not be tolerated in patients who have cardiac defects that depend on mixing of the systemic and pulmonary venous blood to maintain adequate systemic oxygen saturations. This is particularly true if a restrictive communication is present between the two atria. Therefore, ensuring that such patients have an unrestricted atrial communication is important to allow adequate mixing at the atrial level before proceeding with PAB. This can be accomplished with a balloon atrial septostomy or an operative atrial septectomy at the time of PAB.

Indications

Patients who are selected for pulmonary artery banding (PAB) and staged cardiac repair are determined based on the experience and training of the pediatric cardiologists and congenital heart surgeons at any given institution. Most of these patients fall into two broad categories: (1) those with pulmonary overcirculation and left-to-right shunting who require reduction of pulmonary blood flow (PBF) as a staged approach to more definitive repair and (2) those with transposition of the great arteries (TGA) who require training of the left ventricle (LV) as a staged approach to the arterial switch procedure.

Patients in the first category who are considered for PAB include those with the following diagnoses:

  • Multiple muscular ventricular septal defects (VSDs) with a "Swiss cheese" septum that is technically difficult to repair in the neonate or requires a ventriculotomy

  • Single or multiple VSDs with coarctation of the aorta or interrupted aortic arch, or contraindications to primary repair, including very low birth weight, major extracardiac conditions, major chromosomal abnormalities, pneumonia, recovering from shock, sepsis, multisystem organ failure, and intracranial hemorrhage

  • Single ventricle defects (eg, tricuspid atresia) that are associated with increased PBF in the neonate – Some surgeons may elect to perform PAB concomitantly with arch repair if there is distal arch obstruction and coarctation of the aorta, and if the subaortic area, aortic valve, and ascending aorta are felt to be adequate to support the systemic circulation. This may be an option in the setting of unbalanced atrioventricular septal defect, isomerism, and double outlet right ventricle with mitral atresia. However, there is a high unplanned reoperation rate with this strategy, including conversion to the Norwood procedure.[12]

  • Unbalanced atrioventricular canal (AVC) defects in which the LV is hypoplastic but the potential exists for a 2-ventricle repair with further growth and development[13]

  • Cardiac defects that require a homograft conduit (eg, D-TGA with subpulmonic stenosis requiring a Rastelli-type repair) for complete repair: Use of PAB may allow time for growth of the patient before the complete repair. Interim growth of the patient permits placement of a larger conduit at the time of repair and potentially increases the longevity of the conduit and length of freedom from reoperation. With current clinical practice, most patients with D-TGA pulmonary stenosis (PS) undergo a Rastelli procedure and placement of a right ventricle (RV)–to–pulmonary artery (PA) conduit. If a staged repair is indicated, a PAB is not usually performed because of already decreased PBF. In this situation, a systemic-to-pulmonary shunt is performed. Patients with dextro-transposition of the great arteries (D-TGA) with subpulmonic stenosis usually have decreased PBF. The patient who would require PAB in this situation to allow for somatic growth so as to allow a larger conduit to be placed would be rare.

Patients in the second category who are considered for PAB include those with the following diagnoses:

  • D-TGA that requires preparation of LV for an arterial switch procedure following initial late presentation or diagnosis in patients older than 1 month or older than about 6-8 weeks of age with signs of LV deconditioning.

  • D-TGA that requires preparation of LV for an arterial switch procedure following a previous Mustard or Senning procedure with the development of right ventricular failure or L-TGA that requires preparation of the LV prior to the double switch procedure. PAB in patients with corrected TGA will cause the morphologic RV to become less spherical. There will be a shift of the interventricular septum such that there is improved coaptation of the septal leaflet of the tricuspid valve and an improvement in tricuspid regurgitation. Some groups have shown that PAB for preparation of the morphologic RV in corrected TGA may offer satisfactory long-term palliation in this complex group of patients.[14, 15]

Note that patients with single ventricle physiology and unrestricted PBF are suitable for an early PAB to prevent development of congestive heart failure and pulmonary hypertension. This group of patients may include those who have tricuspid atresia with unrestrictive VSD, unbalanced AVC defect, and double inlet LV.[16] In one reported series, 9 of 20 patients with double inlet LV demonstrated severe PA medial hypertrophy on histologic examination within one year of life.[17] Generally, patients who have single ventricle physiology and pulmonary overcirculation should undergo PAB in the first 1-2 months of life to avoid irreversible pulmonary hypertension that may complicate or preclude a subsequent Fontan procedure.

Currently, most patients with D-TGA undergo an arterial switch procedure within the first few weeks of life. However, some newborns with D-TGA and an intact ventricular septum may not undergo an early arterial switch procedure because of active infections, coexistent noncardiac diseases, or a delay in diagnosis.

Because of the risks of neonatal repair, neonates with D-TGA and multiple VSDs may benefit from bilateral PAB prior to definitive repair later in infancy. This technique may be less prone to damaging the neoaortic valve and root dilation than banding of the main pulmonary artery.[18] Patients with Taussig-Bing syndrome who are premature and have low birth weight, as well as have associated anomalies including arch obstruction, chromosomal and major extracardiac anomalies, pneumonia, shock, hepatic and/or renal failure may also benefit from PAB prior to complete repair. The arch repair and PAB may be done initially, followed by arterial switch and VSD repair in 2-4 weeks.

In the past, patients who did not undergo early an arterial switch procedure were treated by a Mustard or Senning procedure because the arterial switch was precluded by rapid involution of the left ventricular myocardium. Subsequent experience demonstrated that neonatal PAB and concomitant systemic-to-PA shunt resulted in preservation of the LV and reversal of any attenuation of the myocardium, leading to successful arterial switch later in infancy.[19, 20]

PAB is also used in patients with D-TGA who develop right ventricular dysfunction after a Mustard or Senning atrial switch procedure. The PAB is required for a longer period than preparation of the ventricle in infants (< 12 months). Although the overall early survival rate approaches 90%, approximately one half of these patients require heart transplantation because of the progression of coexisting left ventricular failure.[21] Furthermore, a high prevalence of significant neo-aortic valve insufficiency is noted in patients who successfully undergo the arterial switch procedure.

Application of PAB has been reported in patients with diagnosis of L-transposition or physiologically corrected transposition of the great arteries.[22] This group of patients may present with failing systemic RV. Using the same principle, the PAB is used to retrain the LV in preparation for a double switch operation, a combination of an atrial and arterial switch.[23, 24, 25]  This operation places the LV as the systemic ventricle and the mitral valve as the systemic AV valve. This achieves anatomic repair of the malformation.

The authors have found another application of PAB in patients with elevated, but reactive, pulmonary hypertension from long-standing left-to-right shunting. An immediate surgical repair may carry significant morbidity and even mortality. With the use of a PAB and pulmonary vasodilator, some of these patients may drop their pulmonary vascular resistance and subsequently respond more favorably to surgery. This approach has been used at the authors' institution with good results.[26]

Relevant Anatomy

In most patients with cardiac defects requiring pulmonary artery banding (PAB), the length of main pulmonary artery (MPA) is sufficient to allow placement of the band in the mid portion of the artery without impingement on either the pulmonary valve, coronary arteries proximally or the branch pulmonary arteries distally. The inferior wall of the right pulmonary artery (PA) arises slightly more proximal on the MPA than the left PA. The right PA also arises from the MPA at more of an acute angle. Both of these factors increase risk of right PA impingement by a distally placed band. The tissue connecting the aorta and MPA in the aortopulmonary window usually must be divided with surgical dissection.

In patients with pulmonary overcirculation, the MPA may be quite large compared to the aorta. Additionally, the MPA vessel wall may be thinned out by this dilatation, and the adventitia may be quite attenuated. These changes increase risk of tearing the wall of the MPA at the time of PAB.

Contraindications

Patients who have single ventricle defects in which the aorta arises from an outflow chamber (eg, double inlet left ventricle [LV], tricuspid atresia with transposition of the great arteries [TGA]) have the potential for development of significant subaortic obstruction. The risk is higher when these lesions are also associated with aortic arch anomalies.[27] Pulmonary artery banding (PAB) is contraindicated in the presence of such obstruction and in patients who are at high risk for such obstruction. The ventricular hypertrophy that develops in response to PAB may cause rapid progression of subaortic obstruction leading to a combination of both ventricles having outflow tract obstruction and progressive hypertrophy.

These patients are identified by careful preoperative assessment, including echocardiography and, if necessary, cardiac catheterization with pullback pressure measurements across the subaortic region. The presence of a gradient more than 15-20 mm Hg or an echocardiographic outlet foramen area index of less than 2 cm2/m2 precludes PAB. Isuprel challenge at the time of cardiac catheterization may expose a gradient across the bulboventricular foramen. The bulboventricular foramen index is described by Matitiau et al.[28]

Instead, these patients should undergo the Damus-Kaye-Stansel procedure and a systemic-to-pulmonary artery shunt.[29, 30] This achieves adequate pulmonary blood flow (PBF) with protection of the pulmonary vasculature and bypasses the subaortic obstruction. Another well-described complication of PAB is the development of subaortic obstruction from conal hypertrophy, particularly in patients with a single ventricle and a subaortic outflow chamber.[31] It may also result from hypertrophy of an abnormally positioned moderator band.

The development or persistence of subaortic stenosis post–PAB can adversely affect outcome of future Fontan procedures through the development of ventricular hypertrophy and consequent subendocardial ischemia.[32] Indeed, the duration of PAB may be an independent risk factor for a subsequent Fontan procedure.[33] If obstruction occurs later, the authors perform a resection of the obstruction or a Damus-Kaye-Stansel procedure, with or without a concomitant Fontan procedure. Earlier cavopulmonary connection may be warranted when anatomy and physiology are appropriate. The operative mortality rate with early intervention remains comparable to the overall group of patients who undergo the Fontan procedure.[34]

PAB is not used in patients diagnosed with truncus arteriosus. Although a main pulmonary artery (MPA) is present in truncus arteriosus type I, it usually is very short and does not allow for successful PAB without impingement on the right pulmonary artery (PA) or the origin of the MPA from the truncal artery. In truncus arteriosus types II and III, bilateral PAB is necessary to effectively reduce PBF.[35] Previous experience has shown that balancing PBF to the right and left lungs is extremely difficult. Furthermore, subsequent complete repair is complicated by bilateral PA stenosis requiring extensive reconstruction. For these reasons, PAB is avoided in this group of patients.

Bilateral PAB may be useful prior to complete repair in the setting of low birth weight, prematurity, major associated extracardiac conditions, severe preoperative acidosis not correctable by medical therapy, pneumonia, as a staged repair in truncus arteriosus with interrupted aortic arch, and/or a combination of these factors. Bilateral PAB can be achieved using a 3.0-mm or 3.5-mm Gore-tex graft placed around the right and left pulmonary arteries as has been described for hypoplastic left heart syndrome (HLHS).[36] Bilateral PAB has also been used as a bridge to decision regarding biventricular versus univentricular palliation. For example, bilateral PAB with maintenance of ductal patency may allow time for adequate growth of a left ventricle so that the infant can undergo biventricular repair. The pulmonary artery bands can also be dilated in case of desaturation, to allow further time before definitive surgery.[37]

Note that early attempts to use PAB in surgical management of HLHS were also unsuccessful.[38] However, more recent reports have shown that, in high-risk patients with HLHS, a hybrid approach of stenting the ductus arteriosus and bilateral PAB may achieve effective short-term palliation.[39, 40, 41, 42, 43, 44] As with the early attempts at PAB in patients with truncus arteriosus, balancing the systemic and pulmonary blood flow and achieving near-equal distribution of blood flow to the right and left lungs can be extremely difficult in these patients. This is a technically delicate and demanding maneuver that, until more data are available, should only be considered in high-risk patients.

As discussed above, bilateral PAB can be achieved using a 3.0-mm or 3.5-mm Gore-tex graft placed around the right and left pulmonary arteries as has been described for HLHS.[36] This group and others have reported a high success rate with the hybrid procedure in HLHS.[45]

 

Workup

Approach Considerations

Routine laboratory tests are obtained preoperatively in the assessment of a patient being considered for pulmonary artery banding (PAB). Baseline arterial oxygen saturations should be obtained by either pulse oximetry or arterial blood gas (ABG) analysis. A baseline creatinine level should be obtained and compared postoperatively during diuresis and management of congestive heart failure (CHF). The hemoglobin and hematocrit should be optimized to improve oxygen carrying capacity and oxygen saturations following PAB.

Imaging and/or diagnostic procedures include echocardiography, magnetic resonance imaging with 3-dimensional reconstruction, and/or cardiac catheterization.

 

Treatment

Medical Therapy

Preoperative treatment of patients with pulmonary overcirculation and congestive heart failure should focus on minimizing left-to-right shunting, improving cardiac function with inotropic support, systemic afterload reduction, and aggressive diuresis. Mechanical ventilator support may be necessary to maintain adequate ventilation and oxygenation in the setting of pulmonary edema. Maintaining higher carbon dioxide levels and lower fraction of inspired oxygen (FIO2) during ventilation may assist in reducing pulmonary blood flow (PBF) and pulmonary edema. If a patent ductus arteriosus is present, attempts should be made to reduce or close it with medical therapy (eg, indomethacin) to reduce this source of PBF.

Surgical Therapy

In the surgical treatment of congenital heart defects, pulmonary artery banding (PAB) is a palliative intervention that is performed as a staged approach to a more definitive surgical repair. The goals of PAB include reduction of pulmonary blood flow to reduce left-to-right shunting and congestive heart failure, protection of the pulmonary vasculature from hypertensive changes, and training of the left ventricle in anticipation of an arterial switch procedure.

Intraoperative Details

Three standard surgical approaches to pulmonary artery banding (PAB) have been established, depending on the need to perform additional procedures at the time of band placement. As an isolated procedure, PAB can be performed through an anterior left thoracotomy in the second or third interspace (see following image).

Pulmonary Artery Banding. The left anterior thorac Pulmonary Artery Banding. The left anterior thoracotomy approach through the second or third intercostal space gives excellent exposure for isolated pulmonary artery banding. Note anatomy of the adjacent structures with medial limits of the incision at the internal mammary vessels. The thymus is swept superiorly away from the phrenic nerve. PA = pulmonary artery; PDA = patent ductus arteriosus.

If performed in conjunction with a coarctation or interrupted aortic arch repair, a left lateral thoracotomy is used and the chest is entered through the third or fourth intercostal space. In both of these approaches, the pericardium is incised anterior to the left phrenic nerve and the thymus is retracted to expose the main pulmonary artery (MPA). A third approach is through a median sternotomy for conditions in which intracardiac procedures (eg, atrial septectomy, partial Senning procedure) requiring cardiopulmonary bypass are indicated. A median sternotomy may also be used in patients with malposed or transposed great vessels in which direct access to the MPA is limited by the position of the aorta through a left thoracotomy approach.

In patients with single ventricle physiology, a median sternotomy incision may be preferred, because it gives excellent exposure to the great vessels in almost any morphology, will allow more precise band placement (so that the branch pulmonary arteries may have less chance of stenosis), improves pulmonary ventilation, allows initiation of extracorporeal membrane oxygenation if there is severe hemodynamic instability, and allows reuse of the same incision for subsequent operations.

Patients may benefit from placement of a band that can be easily and quickly tightened or loosened, both at the initial procedure and during subsequent interventions. The ability to readjust the band is particularly useful in patients who exhibit dynamic changes in cardiac output, pulmonary vascular resistance, and systemic vascular resistance. Additionally, it may benefit patients with significant lung disease (eg, pulmonary edema, atelectasis, pneumonia). Such patients develop severe arterial oxygen desaturation with PAB but may tolerate gradually increasing band tightness as the pulmonary process resolves.

Adjustable bands are also helpful in patients with AV valve regurgitation, particularly complex AV canal defects. The acute increase in afterload that accompanies PAB may exacerbate AV valve insufficiency. Staged tightening of the band is usually well tolerated and allows improvement in insufficiency by decreasing ventricular volume overload. Given the advantages of the adjustable band, this technique is routinely used at the UCLA Medical Center.[46, 47]

Surgical technique

The MPA and aorta are exposed, and the band is prepared for placement. Various banding materials are available, but the authors prefer to use umbilical tape. This material is broad enough to minimize risk of eroding through the PA wall but can still be passed easily through a silastic snare for use as an adjustable band.

The estimated band circumference is marked on the umbilical tape with fine sutures according to the Trusler formula.[48, 49] PAB circumference in patients with noncyanotic nonmixing lesions (eg, ventricular septal defect [VSD]) is 20 mm + 1 mm/kg body weight. For patients with mixing lesions (eg, D-transposition of the great arteries [TGA] with VSD), the formula is 24 mm + 1 mm/kg body weight. In patients with single ventricles in whom the Fontan procedure is planned, an intermediate circumference of 22 mm + 1 mm/kg body weight is preferred. Note that these estimates of band circumference are used simply as guidelines and that the final tightness of the band is ultimately determined by the surgeon using blood gas and PAP measurements at the time of surgery. Systemic oxygen saturations are also used (discussed below).

The site of band placement is carefully selected in the mid portion of the MPA trunk, and distortion or injury to the pulmonary valve or impingement on the branch pulmonary arteries is avoided. Dissection is performed in the adventitia between the aorta and the MPA, and it is limited to prevent proximal or distal band migration. The MPA is handled very carefully because it often is dilated, thin-walled, and susceptible to injury. Regardless of the operative approach, injuries to the posterior wall of the MPA can be difficult to repair because of limited exposure.

Generally, the band is first passed through the transverse sinus to encircle both the aorta and MPA. The aortic end of the band is then carefully delivered between the aorta and the MPA through the previous site of dissection (see following image).

Pulmonary Artery Banding. Safe placement of a pulm Pulmonary Artery Banding. Safe placement of a pulmonary artery band: (A) encircling the aortopulmonary trunk, (B) encircling the aorta, and (C) completing the pulmonary artery band at the final location.

With this technique, the clamp is never passed around the MPA alone and avoids injuries to the artery. This technique is particularly important when PAB is performed through a left thoracotomy on a patient with malposed great vessels.

The marked sites on the band are identified and aligned with each other on the anterior wall of the MPA. The band is snared with a short segment of #8 or #10 polyethylene tubing and fixed with medium hemoclips. A felt or pericardial pledget is placed beneath the band between the end of the snare and the MPA wall to prevent injury to the artery from the snare. The pledget and band material are then anchored to the MPA adventitia to prevent band migration (see following image).

Pulmonary Artery Banding. Pulmonary artery banding Pulmonary Artery Banding. Pulmonary artery banding technique (A-C) using a premeasured Trusler formula adjusted to the cardiac anatomy and physiology. An adjustable device is placed over a felt pledget with adventitial fixation sutures to prevent distal migration. Additional fixation sutures may be placed in the band itself. Each additional medium hemoclip causes approximately 1 mm of change in band circumference. Distal pulmonary artery pressure is measured during tightening.

Tightening the band by the addition of one medium hemoclip is approximately equivalent to a 1-mm decrease in the band circumference. Conversely, removal of a hemoclip enlarges the circumference approximately 1 mm. Instruments for hemoclip application and removal are kept with the patient in the intensive care unit to allow rapid tightening or loosening of the band if necessary. Note that with this technique, no cases of infection or erosion related to the snare have been reported.

Previous experience by the authors' group and others has documented that, although a band is adequate at the time of placement, it may become "too loose" over subsequent weeks and months. This can represent resorption of the internal folds of the vessel wall that are initially present when a circumferential band is placed (see following image).

Pulmonary Artery Banding. Circumferential banding Pulmonary Artery Banding. Circumferential banding of a dilated pulmonary artery can acutely lead to internal infolding of the arterial wall. Later resorption of the infoldings and remodeling of the arterial wall restore a greater internal cross-sectional area.

These acute infoldings of the artery wall further decrease the cross-sectional area of the PA. However, these infoldings resorb with time, restoring a smooth wall and a greater internal cross-sectional area of lumen, a greater PBF, and thus, a looser band.

The authors have modified their technique by decreasing the diameter of the MPA (incisional technique) before applying the band.[50] A partially occluding C-clamp is applied to half of the diameter of the MPA distal to the sinotubular junction (see following image).

Pulmonary Artery Banding. Incisional pulmonary art Pulmonary Artery Banding. Incisional pulmonary artery band yields a fixed reduction of 40% of the vessel diameter before application of a circumferential band.

A perpendicular incision is made into the excluded portion of the artery. The deep V-shaped arteriotomy is closed with a running suture, effectively reducing the diameter of the artery by 40%. An umbilical tape is used with an adjustable snare as described earlier.

In the authors' experience, the incisional PAB has produced a more stable band gradient over time with less requirement for subsequent tightening. It has also eliminated the complication of band migration distally and impingement on the branch pulmonary arteries.

Physiologic assessment to determine the appropriate tightness of the PAB includes intraoperative measurements of the proximal and distal PA pressures, systemic blood pressure, and arterial oxygen saturation by pulse oximetry (or by direct measurement of arterial blood gas sampling). The goal of PAB is to produce a distal PA pressure that is 30-50% of systemic pressure. In general, the authors attempt to achieve saturations of approximately 85-90% with an FIO2 of 50%. Lower saturations of 75-80% may be acceptable in patients with single ventricle physiology. Failure to achieve these levels in patients with mixed circulations suggests inadequacy of the interatrial communication. In such patients, addition of an atrial septectomy or septostomy may be indicated. In addition to changes in PA pressure and systemic oxygen saturation, one ideally should note a concomitant rise in systemic arterial pressure of 10-15 mm Hg.

An adequate atrial communication should be confirmed preoperatively in patients with single ventricle physiology, including transposition with VSD complexes. A balloon atrial septostomy is useful in these situations. Kotani and colleagues measured intraoperative aortic blood flow using a Transonic flow probe and found that aortic blood flow increased by approximately 40% after successful PAB. Their data suggested that higher pre-PAB Qp/Qs (pulmonary [Qs]-systemic [Qp] blood flow ratio) predicted a higher percentage increase in aortic flow. Three patients with less than a 20% increase in aortic blood flow died, required re-PAB, or developed ventricular dysfunction. Aortic blood flow in these patients did not increase even when the band was tightened further than indicated with the Trusler formula. Kotani et al concluded that the limited response to PAB in terms of increases in aortic blood flow is a nonmutable marker of decreased cardiac reserve, as opposed to a parameter that can be targeted by further adjustment of pulmonary artery band circumference (ie, making it tighter). Their current practice is a combination of anatomic (Trusler formula) and physiologic (indexed aortic blood flow pre-PAB and post-PAB, in addition to change in systemic blood pressure and SaO2) assessment during surgery.[51]

One technique applied in patients has been a partial atrial baffle with PAB (see following image). This is used in patients with D-TGA undergoing preparation of the left ventricle for the arterial switch procedure.

Pulmonary Artery Banding. (A) A partial Senning te Pulmonary Artery Banding. (A) A partial Senning technique for improved mixing and saturation and providing both volume and afterload to the left ventricle after pulmonary artery banding. Autologous pericardium is used to baffle the inferior vena cava and the left pulmonary veins across the mitral valve into the left (pulmonary) ventricle, with superior vena cava and right pulmonary vein drainage to the systemic ventricle. The band is best positioned distally to avoid valvular damage in anticipation of the arterial switch procedure. (B) Pulmonary artery banding combined with a modified Blalock-Taussig shunt for rapid preparation of the left ventricle and the arterial switch procedure. This provides left ventricular volume and afterload and can be performed through a left lateral thoracotomy, avoiding the need for a resternotomy at the time of arterial switch. Careful measurement of the proximal pulmonary artery pressure is shown to avoid overtightening the band. PA = pulmonary artery.

With this procedure, the inferior vena caval blood is directed toward the pulmonary (left) ventricle through a pericardial patch baffle. This represents approximately two thirds of systemic desaturated venous return. Conversely, saturated blood returning from the lungs through the right pulmonary veins is directed around the baffle toward the systemic (right) ventricle. This "favorable streaming" results in improvements in saturation and allows placement of an adequately tight PAB for preparation of the LV. This procedure also provides long-term palliation for patients who may not be candidates for the arterial switch procedure. PAB in conjunction with a modified Blalock-Taussig shunt is performed as a closed procedure without CPB and, therefore, is a more desirable approach for short-term preparation of the LV. (See discussion of endoluminal PAB under Future and Controversies.)

PAB takedown is usually performed at the time of the intracardiac repair through a median sternotomy. Generally, the repair is completed first and the PAB removal is performed at the end of the procedure. The band is dissected free from surrounding scar tissue and removed. The area of banding usually remains stenotic and requires repair. This repair can be achieved by resection and end-to-end anastomosis of the proximal and distal MPA or by vertical incision of the MPA followed by pericardial (or polytetrafluoroethylene [PTFE]) patch repair of the arteriotomy (see following image).

Pulmonary Artery Banding. Reconstruction of the pu Pulmonary Artery Banding. Reconstruction of the pulmonary artery after band removal may be accomplished by patch arterioplasty using glutaraldehyde-treated autologous pericardium (A) or polytetrafluoroethylene (PTFE) material (B) or resection of the band site and end-to-end anastomosis using absorbable running sutures (C).

The repair must ensure relief of any branch PA stenosis that may exist as a consequence of the PAB.

Postoperative Details

Patients undergoing PAB are initially treated in the intensive care unit (ICU). They often benefit from a course of intravenous inotropic support and require careful attention to fluid balance and volume status. Following PAB, improved hemodynamics and greater left ventricular output often allow for diuresis and gradual resolution of CHF. The assessment of a patient following PAB should ideally be made under conditions of balanced volume status and in the absence of atelectasis or ongoing pulmonary pathology. Although measured parameters from the operating room are helpful guidelines, the overall clinical status of the patient is the most important assessment. This includes changes in systemic blood pressure, heart rate, oxygen saturation, and overall cardiac function. Hypotension, bradycardia, and ischemic electrocardiographic changes all indicate an excessive band gradient and imminent cardiac failure or arrest.

The advantage of an adjustable PAB is that it allows for rapid loosening of the band with a hemoclip remover in the ICU, if necessary. Catheter debanding is also an invaluable technique in selected cases.[52]

Evaluation of the PAB is made by color flow Doppler echocardiography at the bedside; it usually provides an accurate assessment of band tightness, band gradient, band position, and overall cardiac function. Any impingement or stenosis of the branch pulmonary arteries can also be observed with this study. Rarely, cardiac catheterization and direct measurement of PA pressure and band gradient is necessary. More recently, cinemagnetic resonance imaging[53] and 3-dimensional reconstruction have been useful as noninvasive methods of evaluation.

Follow-up

Most patients undergoing pulmonary artery banding (PAB) for pulmonary overcirculation are monitored for 3-6 months and then undergo more definitive repair of their cardiac defect. Note that the degree of right ventricular hypertrophy that develops in response to any given PAB gradient varies greatly among infants. Those infants who develop rapid and severe right ventricular hypertrophy in response to PAB should be considered for earlier definitive repair to prevent long-term right ventricular dysfunction.

Patients with D-TGA who undergo PAB for training of the LV must be monitored with serial echocardiography to assess "readiness" of the LV before the arterial switch operation. After either technique, patients are monitored with serial echocardiography that allows quantitative measurements of left ventricular mass index, as well as qualitative assessment of ventricular septal geometry. Left-to-right septal bowing is an indication that the LV can generate near-systemic pressure. Left ventricular preparation is usually accomplished within 7-10 days, after which patients may undergo an arterial switch procedure, takedown of shunt, and PAB. The early mortality rate is 4-5%, only slightly greater than that for a primary arterial switch procedure.[54, 55] In infants, this may be several weeks, but older children may require longer periods of banding to achieve adequate results.

In one study, infants who required bilateral PAB as a part of temporary stabling treatment for hypoplastic left heart commonly required additional interventions. Those with a small band applied for longer duration were at the highest risk for interventions.[56]

Complications

Although pulmonary artery banding (PAB) is a seemingly simple operation, it has been associated with numerous complications. One of the most common complications of PAB is impingement and stenosis of one or both of the branch pulmonary arteries. The right pulmonary artery (PA) is involved in most cases of branch stenosis for anatomic reasons already mentioned.

The diagnosis of branch PA impingement is often suggested by a chest radiograph that shows asymmetric vascular markings between the right and left lungs. Definitive diagnosis can usually be made by echocardiography, and fractional pulmonary blood flow (PBF) to each lung can be determined with radionuclide lung perfusion scanning.[57] If significant branch stenosis is uncorrected, it can lead to underdevelopment of the involved lung with alveolar hypoplasia.[58] Early recognition of branch PA stenosis should allow a revision of the PAB before the development of this late sequela. Limiting dissection of the tissue between the aorta and the main pulmonary artery (MPA) and fixing the band with sutures on the proximal MPA adventitia both reduce risk of this complication. Use of the incisional PAB technique prevents distal band migration and generally avoids this complication.

Conversely, if the band is placed too proximal on the MPA, it may distort the pulmonary valve and ultimately create dysplastic changes in the pulmonary valve leaflets. This is particularly devastating when PAB is performed as preparation for an arterial switch procedure because the pulmonary valve becomes the neo-aortic valve after the arterial switch procedure. In addition, proximal placement of the band can lead to obstruction of coronary blood flow by direct impingement, usually of the circumflex coronary artery. Anomalous origin of a coronary artery may increase risk of this complication.[59, 60] These complications can generally be avoided by placement of the band more than 15 mm distal to the pulmonary valve cusps.[61] Preoperative demonstration of coronary anatomy is helpful, but intraoperative vigilance during the banding procedure should avoid these types of complications.

In patients with erosion of the band into the PA, scarring and fibrosis around the band site usually prevents the life-threatening bleeding from occurring. Hemolytic anemia and local thrombus formation have been reported.[62] Erosion seems to occur with increased frequency when narrow banding material is used, although it can occur with any material. PA pseudoaneurysm is a rare complication of PAB. It may be preceded by local infection and, like band erosion, is heralded by loss of the band murmur and gradient. Imaging studies demonstrate an enlarged mediastinal shadow on chest radiography and a markedly enlarged PA on echocardiography or MRI. The diagnosis of PA pseudoaneurysm formation mandates urgent surgical intervention. Repair is performed on cardiopulmonary bypass with patch repair of the MPA. Glutaraldehyde-treated autologous pericardium is preferred to synthetic material because this condition is sometimes associated with infection.

An additional complication is an ineffectual PAB either from a loose band at the original procedure or later disruption of the band or erosion of the PA. In earlier studies, ineffectual banding occurred in as many as 15-20% of patients undergoing PAB.[63] The results of an ineffectual band are excessive PBF and early recurrence or continuation of congestive heart failure (CHF). In addition, pulmonary vascular disease with irreversible pulmonary hypertension may potentially develop. Loss of band murmur and recurrence of CHF after PAB suggests loosening or erosion of the band. Furthermore, subsequent improvement may herald the onset of pulmonary vascular disease with a decrease in left-to-right shunting.[64] Early evaluation and close follow-up should allow revision before the onset of irreversible changes.

Outcome and Prognosis

Pulmonary artery banding (PAB) should result in improved hemodynamics and overall clinical improvement in the patient. The signs and symptoms of congestive heart failure (CHF) should resolve or become medically manageable, cardiomegaly should decrease, and pulmonary vascular resistance should decrease. PAB affords protection to the pulmonary vasculature against fixed irreversible pulmonary hypertension secondary to pulmonary overcirculation and elevated pulmonary artery (PA) pressures.

The mortality rate of PAB is clearly associated more with the complexity of cardiac defect and overall condition of the patients than with the procedure itself. Patients who are selected for PAB and a staged repair are often chosen because they are considered too high risk to undergo definitive repair. Therefore, the mortality rates from earlier series have been as high as 25%.[65] A decreasing mortality rate with PAB can be related to improved operative techniques, better patient selection, and timing of intervention.[66, 67, 68, 69] Additionally, improvements in anesthetic and postoperative management have also resulted in a decreased mortality rate. Mortality rates for PAB are reported in some series to be as low as 3-5%.

PAB remains in STAT (The Society of Thoracic Surgeons-European Association for Cardiothoracic Surgery) category 4 of 5 for mortality ranking. As previously noted, the mortality risk of PAB is associated with the complexity of the cardiac defect and the overall condition of the patient.[70]

Future and Controversies

Almost half a century since the introduction of pulmonary artery banding (PAB) by Muller and Danimann, this procedure still has a defined role in the treatment of infants who are not candidates for immediate definitive repair. In particular, it may be useful in patients with a functional single ventricle not amenable to early repair and in whom a future Fontan procedure is planned. It may also benefit patients with excessive pulmonary blood flow who are considered too ill to undergo complete repair of their cardiac defect. Interestingly, the original technique of an incisional band as described by Muller and Danimann has resurfaced as a desirable technique in some patients.

The adjustable band technique has proved useful and safe for most patients. Interest has been shown for the development of an intraluminal technique for PAB using circular patches of fenestrated material.[71] This requires a cardiopulmonary bypass to perform and is therefore limited in its applicability to most patients. Ongoing research to develop a percutaneously adjustable, thoracoscopically implantable, pulmonary artery band is underway.[72]

Additionally, research is being conducted in animals to develop a hydraulic main pulmonary artery (MPA) constrictor as an adjustable PAB.[73] These types of devices would benefit patients who require multiple adjustments of a PAB for left ventricle (LV) training. An implantable device for PAB with telemetric control, FloWatch-R-PAB (Endoart SA, Lausanne, Switzerland) has emerged from animal studies and is currently in clinical trials.[74, 75] Early clinical results have shown the efficacy and reliability of the device, but more data and experience are needed to define the role of this technology in PAB. A percutaneously adjustable PAB technique has been developed for LV training.[76] Other groups have developed percutaneously adjustable devices.[77]

A strategy of deferring biventricular repair by the application of a pulmonary artery band may not be applicable in developing and third world conditions primarily due to lack of patient compliance. A study by Brooks et al indicates that less than 50% are eventually repaired in a reasonable time frame. Moreover, patient follow-up is unreliable. Thus, in such circumstances, consideration should be given to early definitive repair, even in perceived high-risk cases.[78]

PAB has been proposed as a treatment modality for LV dilated cardiomyopathy with preserved RV function as an additional strategy to delay or even avoid heart transplantation in infants and young children with terminal heart failure.[79] The rationale is similar to that for training of the morphologic LV in corrected transposition of the great arteries (TGA).

For most patients undergoing PAB, the goal of the procedure remains reduction of pulmonary blood flow (PBF) and preservation of pulmonary vessels from hypertrophy and hypertension. A new indication of preparing the LV for arterial switch in older infants and children with D-TGA appears to have expanded the role of this procedure. Although some surgeons would contend that PAB is largely of historical interest, this technique clearly will continue to maintain a place in the therapeutic armamentarium of the congenital heart surgeon.[80]