Palliative Operations

Palliative Operations

Carl L. Backer1 and Constantine Mavroudis2

1UK Healthcare Kentucky Children’s Hospital, Lexington, KY, USA

2Peyton Manning Children’s Hospital, Indianapolis, IN, USA

The word “palliate” originates from the Latin palliare (“to cloak”) and in medicine it is usually taken to mean the masking or lessening of an effect [1]. A palliative operation generally is one that provides symptomatic relief but leaves the main pathophysiology uncorrected. A palliative operation is one that affords relief (usually temporary) but is not a correction or a repair. In congenital heart surgery the two classic palliative procedures are the aortopulmonary shunt and the pulmonary artery band [2, 3]. From a historical perspective, these were initially the only procedures available to treat many children with congenital heart disease. Over the past 70 years the advances in open‐heart surgery, progressing to neonatal repair for many congenital heart lesions, have decreased markedly the indications for these palliative procedures. Although there are fewer and fewer indications for palliative procedures, there is a select, small group of patients for whom palliation is still (and may always be) necessary. The importance of the initial palliative procedure cannot be overemphasized [4]. A poorly performed aortopulmonary shunt that destroys a pulmonary artery may prohibit the child from having a completion Fontan procedure. Hence, although these are older and seemingly less important procedures, they must be performed well to ensure a smooth eventual “corrective” procedure.

Some of the procedures reviewed in this chapter are now actually considered obsolete and are no longer performed. However, the surgeon must understand these procedures and their attendant complications, because there are surviving patients who have had these operations in the remote past but now require repeat surgical intervention. A thorough understanding of palliative procedures is necessary for appropriate staging and successful takedown at the time of correction. A relatively new alternative to the surgical aortopulmonary shunt is the transcatheter placement of a ductal stent [5, 6]. In properly selected patients this is rapidly becoming the procedure of choice [7].

In general, the goals of palliative procedures are to alter the hemodynamic physiology in such a manner as to make the cardiac malformation more tolerable, enable an improvement in the patient’s condition, and allow continued growth until the child has the next procedure. In the past, palliative procedures were performed on nearly all children and their complete “correction” was performed when they were older and larger. With improvements in cardiopulmonary bypass and in microsurgical techniques, the size of the patient is no longer as significant a consideration in deciding between palliation and complete repair. Rather, it is the underlying cardiovascular physiology, in particular the normal high neonatal pulmonary vascular resistance, that usually mandates a palliative operation in the current era.

The two primary palliative procedures are aortopulmonary shunts (Table 8.1) and the pulmonary artery band. Many of the aortopulmonary shunts noted in Table 8.1 are now obsolete and rarely used (Potts shunt, Waterston/Cooley shunt). Aortopulmonary shunts are designed to increase pulmonary blood flow in a cyanotic child with inadequate pulmonary blood flow. A pulmonary artery band is designed to limit pulmonary blood flow in a child with excessive pulmonary blood flow. A third palliative operation is the atrial septectomy, designed to increase mixing at the atrial level in patients with transposition of the great arteries or functionally univentricular heart and atrioventricular valve stenosis. The Blalock–Hanlon atrial septectomy was first reported in 1950 [8]. Interestingly, like many other “simple” congenital heart procedures, this is now most commonly performed using transcatheter techniques [9]. There are other, more complex procedures that are considered palliative, such as the Norwood operation for hypoplastic left heart syndrome [10] and the Glenn procedure [11], but these are in general specific operative procedures for defined lesions and are discussed in detail in the chapters on those specific lesions. One palliative operation that has had a resurgence is pulmonary artery banding combined with a ductal stent for hypoplastic left heart syndrome, the so‐called hybrid approach [1214].

Table 8.1 Aortopulmonary shunts.

Shunt Surgeon Year
Blalock–Taussig–Thomas shunt Alfred Blalock 1944
Potts shunt Willis Potts 1946
Waterston shunt David Waterston 1962
Cooley shunt Denton Cooley 1966
Modified Blalock–Taussig–Thomas shunt Marc de Leval 1976

Pulmonary Artery Band

Pulmonary artery banding was first reported by Muller and Dammann [3] in 1952 for children with a large left‐to‐right shunt or functionally univentricular heart and excessive pulmonary blood flow. For many years, pulmonary artery banding was the preferred initial palliation for any small child with a large left‐to‐right shunt and increased pulmonary blood flow. Examples of this would include ventricular septal defect, atrioventricular septal defect, and common arterial trunk. However, as improvements in neonatal cardiac surgical techniques have taken place, pulmonary artery banding is now routinely used for only a very few specific lesions. These include (i) “Swiss‐cheese” muscular ventricular septal defects; (ii) multiple ventricular septal defects or atrioventricular septal defect with coarctation; (iii) functionally univentricular heart with increased pulmonary blood flow (i.e., tricuspid atresia type IIc) [15, 16]; (iv) to prepare and retrain the left ventricle of a patient with transposition of the great arteries for the arterial switch procedure, either following late presentation after 4 weeks of age [17] or following prior atrial repair [18]; (v) to train the left ventricle in a patient with congenitally corrected transposition of the great arteries for a “double switch” [1921]; and (vi) the critically ill infant with contraindications for the use of cardiopulmonary bypass. These indications are in some cases controversial. For example, some surgeons recommend a Damus–Stansel–Kaye procedure with aortopulmonary shunt instead of pulmonary artery band placement for functionally univentricular heart with increased pulmonary blood flow, especially when there is potential for subaortic obstruction [22, 23].

Pulmonary artery banding in a child with normally related great vessels can be performed through either a left lateral thoracotomy or a median sternotomy incision. Although the left thoracotomy was historically the preferred approach, many surgeons now prefer the median sternotomy approach. The advantage of the left thoracotomy approach is that it frees the anterior mediastinum from adhesions at the time of reoperation. The advantage of the median sternotomy is that it allows a safe and usually quite easy approach to the pulmonary artery, even with the frequently varied location of the pulmonary artery in complex defects (e.g., heterotaxy, situs inversus, etc.). In addition, as the band is tightened, the saturations reflect only the banding and not also the effect of the lung compression from a thoracotomy. Resternotomy is no longer a technical issue because it is such a common event for most surgeons [24]. The bands we have used are either Teflon‐impregnated Dacron (infants) or a strip of polytetrafluoroethylene (PTFE) (neonates).

Figure 8.1 shows the approach for a pulmonary artery banding through a median sternotomy incision. The thymus is either divided in the midline or partially removed. Only the upper portion of the pericardium needs to be opened. If a left thoracotomy is used, the pericardium is opened anterior to the phrenic nerve. Stay sutures are placed to hold the pericardium open. The left atrial appendage generally sits just at the site where the band is to be applied and it can be retracted with a stay suture if needed. Directly encircling a dilated, thin‐walled pulmonary artery can possibly lead to unwanted pulmonary artery entry and thus needs to be performed with great care. The safest way to encircle the pulmonary artery is by the subtraction technique. This is illustrated in Figure 8.1A. The band is first placed around both the aorta and the main pulmonary artery proximally. This initial maneuver also avoids the complication of encircling only the left pulmonary artery, which can happen with the thoracotomy approach. A plane is then developed between the aorta and the pulmonary artery with a combination of sharp dissection and electrocautery. A right‐angled clamp is passed around the aorta (not the pulmonary artery) and the free end of the band is grasped (Figure 8.1A2). The band is pulled through the space between the aorta and pulmonary artery and (by subtraction technique) encircles the pulmonary artery. The band is then sequentially tightened by placing multiple interrupted sutures in the band, as illustrated in Figure 8.1B. An alternative technique to tighten the band is with serial hemoclips, each placed below the prior clip, leading to a progressively tighter band.

To determine an initial pulmonary artery band circumference, we have used the Trusler formula. The original Trusler formula for pulmonary artery banding was to make the band circumference 20 + 1 mm for each kg of body weight [26, 27]. The formula has been modified by Baslaim [28] to place a band that was 2.25 mm narrower in the functionally univentricular heart group. A catheter can be placed in the distal pulmonary artery to monitor the distal pulmonary artery pressure in comparison with the aortic (radial) pressure as the band is being tightened (Figure 8.1C). Alternatively, the gradient across the band can be monitored by transesophageal echocardiography. Once the band has been tightened to the desired degree, the band is fixed to the proximal pulmonary artery with several interrupted polypropylene sutures to prevent distal migration of the band and encroachment on the right pulmonary artery (Figure 8.1C).

Schematic illustration of placement of pulmonary artery band.

Figure 8.1 Placement of pulmonary artery band. (A, 1–3) Encircling the pulmonary artery by the subtraction technique. (B, 1–3) Suture placement to tighten the band. (C) Pressure monitor in distal pulmonary artery to assess band tightness. Ao, aorta; PA, pulmonary artery. Source: Reproduced with permission from Backer CL, Mavroudis C, in Pediatric Cardiac Surgery, Philadelphia, PA: Mosby, 2003, pp. 160–170.

Placement of the band should result in an elevation of the aortic systolic blood pressure by 10–20 mmHg. For a patient who will eventually have a two‐ventricle repair, the distal pulmonary artery systolic pressure should be reduced to less than 50% of the measured aortic systolic blood pressure. For a patient who is going to undergo an eventual Fontan procedure, the lowest possible distal main pulmonary artery pressure that can be achieved with acceptable oxygen saturations is desired. Oxygen saturations for a patient who is going to undergo biventricular repair should be left at 95%. For the patient who is going to undergo a Fontan operation, the oxygen saturation should preferably drop to between 80% and 85%. It should be kept in mind that as the child grows, the band will by default become “tighter” and further lower the distal pulmonary artery pressure (and saturations). One possible complication of band placement is the above‐noted encroachment on the right pulmonary artery. The band can pinch off the right pulmonary artery while allowing excessive blood flow to the left pulmonary artery. This results in right pulmonary artery stenosis and left pulmonary artery hypertension. This complication can be avoided by properly anchoring the band to the proximal main pulmonary artery. Once the band has been secured in place, the pericardium is irrigated with saline, so there is less chance of intrapericardial adhesions at the time of intracardiac repair. If performed through a left thoracotomy, the pericardium is loosely approximated with several interrupted polypropylene sutures, with care being taken to avoid injury to the phrenic nerve.

Although the concept of an externally adjustable pulmonary artery band has been around for many years, it is only recently that several alternative techniques have been reported, with considerable improvement in results. DiBardino reported a method of a transcutaneously placed adjustable band [21]. Corno reported the use of a patented device − FloWatch®‐PAB (EndoArt, Lausanne, Switzerland) [29] that was in use in Europe and Asia between 2002 and 2012. Production of the device ceased, but in 2016 rights to the FloWatch device were transferred to espeRare, a nonprofit organization, which launched a program to bring an improved device to market [30]. The device produced in the past was a small “clip”‐like device with a telemetric‐controlled incorporated electric micrometer. The meter drove a piston that changed the area inside the clip. Because this band compresses the pulmonary artery in a noncircular fashion, pulmonary artery reconstruction may not be required when it is removed [31].

The total number of pulmonary artery band procedures reported in the Society of Thoracic Surgery (STS) congenital database was 2522 for the period from 2015 to 2018, corresponding to 2.1% of the total surgical procedures (2522 of 118,794). The total number of pulmonary artery banding procedures reported in the European Association of Cardio‐thoracic Surgery (EACTS) congenital database was 711, corresponding to 2.0% of the total surgical procedures (711 of 35,575) [32]. These figures contrast with the opinion that pulmonary artery banding is an abandoned procedure [33]! Devlin recently reported excellent results with the use of pulmonary artery band placement in selected high‐risk patients with complete atrioventricular septal defect [34]. This included premature infants, infants with unbalanced atrioventricular septal defect, coarctation of the aorta, and other serious comorbidities. In a multi‐institutional study, Shuhaiber and colleagues [35] studied neonates with atrioventricular septal defect and aortic arch obstruction. When compared with attempted complete neonatal repair, a staged approach with prior pulmonary artery banding was associated with improved survival and lower morbidity, including fewer complications and unplanned reoperations.

Another method of pulmonary artery band placement is the “intraluminal” technique [36]. This technique is used only in patients who require cardiopulmonary bypass for other, simultaneous procedures. The technique utilizes a patch with a calibrated precut hole in the center that is sutured as a patch in the main pulmonary artery. It results in a consistent and significant reduction in pulmonary artery pressure and flow. It essentially eliminates the problem of band “slipping,” with resultant pinching of the right pulmonary artery. One of the advantages of this “band” is that it can be dilated with transcatheter techniques if the patient should become progressively cyanotic with growth. Pulmonary artery band takedown is performed by incising the pulmonary artery, resecting the patch, and then performing an end‐to‐end anastomosis. Many of the patients, however, who have the intraluminal band go on to a bidirectional Glenn (Fontan strategy), in which case the pulmonary artery is transected at the site of the patch.

Schematic illustration of takedown of a pulmonary artery band.

Figure 8.2 Takedown of a pulmonary artery band. (A, 1–3) Pulmonary artery transection, removal of the band site, and end‐to‐end reconstruction with interrupted absorbable suture. (B) Takedown of a pulmonary artery band with anterior polytetrafluoroethylene (PTFE) patch placement. LPA, left pulmonary artery; PA, pulmonary artery; PAB, pulmonary artery band; RPA, right pulmonary artery. Source: Reproduced with permission from Backer CL, Mavroudis C, in Pediatric Cardiac Surgery, Philadelphia, PA: Mosby, 2003, pp. 160–170.

Pulmonary artery band takedown is performed at the time of intracardiac correction of the congenital cardiac lesion through a median sternotomy. Generally, the intracardiac repair is performed first, and the pulmonary artery reconstruction can be done while the patient is being warmed. All portions of the band should be removed, because even a small portion of Dacron band left posteriorly can create scarring, which can cause late pulmonary artery stenosis. Removing the band completely, however, is not always adequate to prevent residual pulmonary stenosis at the band site, because the pulmonary artery wall does not easily rebound open. If the band is left in place for only a period of weeks, simple removal is adequate. If the band is left in place for more than a few months, however, the area of banding must be either patched anteriorly or excised (Figure 8.2). The technique of excision of the scarred pulmonary artery banding site is shown in Figure 8.2A. The area where the band was positioned is resected and then an end‐to‐end anastomosis is performed between the two remaining pulmonary arterial segments with absorbable, fine monofilament suture. The distal right and left pulmonary arteries must be completely mobilized and the ligamentum arteriosum ligated and divided to provide a tension‐free anastomosis. The patch technique is illustrated in Figure 8.2B. A patch of either pericardium or PTFE is used to augment the pulmonary artery anteriorly over the posterior scarred area and allow flow into the right and left pulmonary arteries without hemodynamic obstruction to flow. This sometimes requires use of a “pantaloon” patch with extension into the right and left anterior sinuses of Valsalva. Although most surgeons have preferred to use a patch anteriorly, this usually still results in a mild main pulmonary artery stenosis and residual murmur. The use of transection of the site of the band and direct end‐to‐end anastomosis in most cases results in no gradient and no residual murmur. As mentioned previously, use of the newer adjustable bands may help prevent the need for pulmonary artery construction [31].

Recently, surgeons have described two novel uses for pulmonary artery bands. Schranz reported a small series of patients with left ventricular dilated cardiomyopathy who were referred for heart transplantation [37, 38]. Banding of the pulmonary artery led to an improvement of left ventricular and mitral valve function by ventricular interaction. Ma et al. reported the use of pulmonary artery banding in patients with congenitally corrected transposition of the great arteries that led to both left ventricular training and improved tricuspid regurgitation (systemic atrioventricular valve) [39]. This appears to occur because of a shift in the ventricular septum back to a more “normal” midline position. In selected patients they recommend prolonged palliative pulmonary artery banding over double switch.

Aortopulmonary Shunts

Classic Blalock–Taussig–Thomas Shunt

The Blalock–Taussig–Thomas (BTT) shunt was the first aortopulmonary shunt and was performed in 1944 by Alfred Blalock with the assistance of Vivien Thomas of the Johns Hopkins University Medical Center [2, 40]. The classic BTT shunt (previously known as the Blalock–Taussig shunt) is a direct end‐to‐side anastomosis of the transected subclavian artery to the pulmonary artery. Blalock and Thomas had successfully created a left subclavian‐to‐pulmonary artery anastomosis while developing a canine model of pulmonary hypertension at Vanderbilt University. Helen Taussig suggested that they apply their experimental procedure to patients who had cyanosis from insufficient pulmonary blood flow. The first operation was performed on November 28, 1944, on a 15‐month‐old girl with the diagnosis of tetralogy of Fallot and severe pulmonary stenosis. This was truly the dawn of a new era [41]. After that first successful case, hundreds of cyanotic children went to Baltimore for “the operation.” In fact, between 1944 and 2006, 2016 patients had a Blalock–Taussig shunt at Johns Hopkins Medical Center [42].

The classic BTT shunt was constructed through a thoracotomy approach on the side opposite the aortic arch. When there is a left aortic arch, there is typically a right innominate artery, and using the subclavian artery on this side provides a gentle curve to the pulmonary artery. With a right aortic arch and mirror‐image branching, the left innominate artery provides a similar gentle curve to the left pulmonary artery. In contrast, the contralateral subclavian artery would require an angulation of the artery of nearly 180 degrees for the anastomosis. Figure 8.3 illustrates the anatomy for exposure of the right subclavian and pulmonary arteries through a right thoracotomy. The branches of the right subclavian artery are ligated and divided along with the distal subclavian artery, and the subclavian artery is pulled through the loop formed by the right recurrent laryngeal nerve. The carotid artery can be dissected to provide more mobility. The azygos vein is doubly ligated and divided. The anastomosis is constructed to the main pulmonary artery with vascular clamps after 1 mg/kg of heparin is given intravenously. Care is taken to avoid the complication of performing the anastomosis to the right upper lobe branch. The subclavian artery will then lie in a groove just posterior to the superior caval vein and the phrenic nerve. Takedown of the classic right BTT shunt at the time of complete correction through a median sternotomy involves dissection posterior to the superior caval vein. The artery can then be encircled and double ligation performed.

Schematic illustration of classic Blalock–Taussig shunt (right thoracotomy).

Figure 8.3 Classic Blalock–Taussig shunt (right thoracotomy). RPA, right pulmonary artery; SVC, superior caval vein. Source: Reproduced with permission from Backer CL, Mavroudis C, in Pediatric Cardiac Surgery, Philadelphia, PA: Mosby, 2003, pp. 160–170.

The classic BTT shunt does not require prosthetic material and provides a precise amount of pulmonary blood flow limited by the orifice of the subclavian artery. The shunt grows with the patient, providing more pulmonary blood flow as the child grows. However, the BTT shunt sacrifices the subclavian artery, which in a small number of cases can result in hand or arm ischemia [43]. The affected arm is usually shorter than the contralateral arm, is often somewhat cool to the touch, and will not have a palpable pulse. In addition, even with ample mobilization of the carotid artery and division of the inferior pulmonary ligament, the subclavian artery may still be so short as to cause the pulmonary artery to be “pulled” up and kink. Because of the multiple disadvantages of the classic BTT shunt, essentially all centers now use a PTFE graft and preserve the subclavian artery.

Modified Blalock–Taussig–Thomas Shunt

The use of a PTFE tube for an aortopulmonary shunt was first reported by Gazzaniga and associates in 1976 [44]. DeLeval [45] coined the term modified Blalock–Taussig(–Thomas) shunt when he reported on 99 patients operated on between 1975 and 1979. The advantages of the modified BTT shunt, which has now become the shunt of choice at most congenital heart surgery centers, include (i) preservation of the circulation to the affected arm; (ii) regulation of the shunt flow by the size of the shunt; (iii) guarantee of adequate shunt length; and (iv) ease of shunt takedown. One disadvantage of the modified BTT shunt is the occasional leaking of serous fluid through the interstices of the fabric of the PTFE. This may result in excessive and prolonged chest tube drainage, localized seroma formation around the graft, or both [46]. This complication occurs in less than 5% of patients. The patency rate of the modified BTT shunt has been improved by the addition of heparin coating to the PTFE graft [47, 48].

The modified BTT shunt can be performed through a right or left thoracotomy or a median sternotomy. The approach depends on the subclavian and pulmonary artery anatomy, the presence and location of a patent arterial duct, the great vessel relationship, and surgeon preference. For many years there has been a distinct preference at most centers for performing the modified BTT shunt through a median sternotomy. This has been our approach of choice for over 20 years. The sternotomy approach is technically less challenging and is associated with fewer shunt failures than the classic thoracotomy approach [49]. If necessary, the shunt can be performed with the use of cardiopulmonary bypass if the child has significant oxygen desaturation during the procedure. With a median sternotomy approach the side of the aortic arch is not a concern. The shunt can also be taken from the main pulmonary artery (central shunt), which is preferable in many cases. Access to the patent arterial duct for ligation to remove a source of competitive flow is always possible. The potential theoretical disadvantage of increased adhesions at the time of sternal reentry has not really been an issue [24].

The size of the PTFE graft selected is based on the size of the patient. Importantly, the amount of flow through the shunt is determined by Poiseuille’s law,

upper Q equals StartFraction pi r Superscript 4 Baseline upper Delta p Over 8 mu normal upper L EndFraction

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May 18, 2023 | Posted by in CARDIOLOGY | Comments Off on Palliative Operations
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