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a Cardiothoracic Centre, All India Institute of Medical Sciences, New Delhi, India
b Department of Biostatistics, All India Institute of Medical Sciences, New Delhi, India
Accepted for publication July 19, 2007.
* Address correspondence to Dr Choudhary, Department of Cardiothoracic and Vascular Surgery, All India Institute of Medical Sciences, New Delhi 10029, India (Email: shivchoudhary{at}hotmail.com).
| Pediatric cardiac surgery:
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Abstract |
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 Top Abstract IntroductionPatients and MethodsResultsCommentReferences |
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Methods: Between June 2001 and June 2006, 147 patients underwent PAB: 91 underwent CPAB and 56 underwent APAB.
Results: The clinical profile of patients was similar in both groups. Inotropic drugs were used in 91 (100%) patients in the CPAB group and in 12 (21%) in the APAB group (p < 0.001). Early band related reoperation was required in 17 patients in the CPAB group compared with 2 patients in the APAB group (p = 0.014). There were 21 (23%) early deaths in CPAB group compared with 1 (1.8%) in the APAB group (p < 0.001). There was no difference in the intensive care unit stay, hospital stay, and final band gradients in the two groups. On a mean follow-up of 22.8 ± 18.6 months (range, 4 to 72 months), there was PA distortion in 6 patients and band-migration in 4 patients in the CPAB group. These were not observed in the APAB group.
Conclusions: Similar band gradients were achieved with the use of conventional or adjustable PAB. However, the use of this simple and inexpensive technique of APAB was associated with a significant reduction in the early band-related deaths, need for early multiple reoperations, and early adverse acute events, thus making it a safer alternative to CPAB, more so in unstable patients.
Since pulmonary artery banding (PAB) was first performed by Muller and Dammann [1], its indications have gradually diminished due to a gradually increasing trend towards early primary repair of more complex cardiac malformations. However, it is still a useful initial palliation for patients with multiple ventricular septal defects, to reduce the excessive pulmonary blood flow in patients with single ventricle physiology, and for retraining the left ventricle as a part of the rapid two-stage arterial switch operation [2–7].
Conventional PAB (CPAB) has always been associated with high morbidity and mortality and a high reoperation rate, which has not diminished appreciably [8–11]. This has prompted development of the concept of adjustable PAB (APAB), where the pulmonary blood flow can be controlled to tide over a period of hemodynamic instability in these patients who often do not tolerate a sudden increase in the after load to the ventricle. A wide variety of APAB systems have been developed, which are technically complex and expensive [12–16]. We have also developed a simple and inexpensive technique of APAB and reported this technique recently [17]. In this report, we discuss our experience with PAB during the 5 years and compare the outcomes obtained with the use of either conventional or adjustable PAB.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Only patients requiring isolated PAB were included in this study. Exclusion criteria included patients requiring repair of coarctation of aorta, atrial septectomy, and those requiring the addition of a systemic-to-pulmonary artery shunt for retraining the left ventricle in the setting of transposition of great arteries and intact ventricular septum with low left ventricular pressures. The demographic features and underlying cardiac diagnosis are listed in Table 1.
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A purse string suture was used to place a 23-gauge needle in the distal MPA to monitor the PA pressure. At this stage, the inspired oxygen concentration (FIO 2) was set to 50%, and the adequate band length was achieved while monitoring the distal PA pressure, systemic saturation, and the hemodynamics.
In patients with noncyanotic, nonmixing lesions, such as a ventricular septal defect, the initial circumference of the band was set at 20 mm + 1 mm/kg body weight. In patients with single ventricle physiology, it was set at 22 mm + 1 mm/kg body weight. This was used as the starting point for the banding, and adjustments in band width were made by monitoring the overall hemodynamic status, systemic oxygen saturation, and PA pressures. In general, we attempted to reduce the PA pressures to about one-third of the systemic arterial blood pressure.
Once the PAB was considered to be optimal, the two ends of the Merselene tape were fixed using 2 to 3 clips (LT 200 Ethicon), and the band was transfixed to the adventitia of the MPA using 5-0 polypropylene suture to prevent migration.
We described the technique of APAB recently in detail [17]. This is illustrated in Figure 1. In brief, in this technique, the MPA was looped with a No. 2 Ethibond (Johnson & Johnson Inc, Somerville, NJ) suture after passing a right-angle forceps between the aorta and the MPA. This right-angle forceps was again passed and the suture end was grasped again, so that the MPA was doubly looped. The two ends of this suture were passed through a 0.5 x 0.5-cm polytetrafluoroethylene (PTFE) pledget, which was anchored to the adventitia of the MPA using interrupted 5-0 polypropylene suture. Both arms of the suture were clipped together with a Liga clip (LT 200; Ethicon Endosurgery Inc, Cincinnati, OH) just on the pledget. These sutures were brought out through the pericardium and the lateral edge of the sternum and then through subcutaneous tissue and skin. After sternal closure, the two ends of the suture were passed through another 1 x 2-cm PTFE pledget, and these were clipped together with a big Ligaclip (LT 400, Ethicon Endosurgery). The ends of the suture were then tied to form a loop.
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In the APAB group, the tightening of the band was started in the ICU whenever possible after the patient was extubated and breathing room air. If heart failure was believed to preclude early extubation, the band was tightened just enough to achieve extubation and the final band tightening was done only after the patient was extubated and breathing room air. The treating surgeon performed band tightening by placing additional big clips (LT 400, Ethicon Endosurgery) outside between the PTFE pledget and the previous clip under pulse oximetry guidance while the cardiologist performed transthoracic echocardiography. Typically, the tightening was performed in three to six sessions during a period of 4 to 7 days, and no more than a 30 mm Hg gradient was added at a time. Most patients required four sessions to achieve an adequate gradient.
In two ventricle candidates, a gradient of approximately 60 mm Hg across the band was the target with a minimally acceptable systemic saturation of 85%. In univentricular candidates, maximal band tightening was achieved taking care that the systemic saturation always exceeded 75% and there was no hemodynamic compromise. If systemic desaturation and bradycardia occurred during band tightening, the last clip was removed and the two threads were allowed to retract inside. All patients in the APAB group received antibiotic prophylaxis while the band was outside.
Once satisfactory gradients were achieved, the band was internalized by making a small opening in the subcutaneous plane and clipping the two threads together. The sutures above this were cut, and the wound was closed. The patients were discharged only after internalization and no subsequent adjustments were made.
After discharge from the hospital, the patients were seen in the outpatient clinic after 1 month and then once every 3 months. At each visit, they were assessed clinically, their peripheral saturation was measured, and echocardiography was performed for band gradients, for estimating pulmonary artery pressures, and to assess the ventricular function. Before definitive surgery, all the patients underwent complete cardiac catheterization and angiography for estimating the PA pressure and to rule out band migration or PA distortion, or both. Their last follow-up visit between July and September 2006 was recorded and was used for reporting the results.
Statistical Analysis
Statistical analysis was done with SPSS 11.5 software (SPSS, Chicago IL). Descriptive statistics, including mean, median, standard deviation, and frequency, were calculated for each variable. To assess the differences between two groups, the Student t test was used for continuous variables and the 
2 test was used for categoric variables. Stepwise logistic regression analysis was performed to assess the effect of each variable on the early mortality and band-related acute events.
For the purposes of assessing early outcome and morbidity, a band-related adverse event was defined as any episode of sudden cardiac decompensation requiring reinstitution of mechanical ventilatory support or increasing inotrope requirement, or both, ventricular arrhythmias necessitating resuscitation, sudden unexplained death, or any event requiring reoperation for loosening or tightening of the band. A value of p < 0.05 was considered statistically significant.
A band-related death was defined as death occurring within 1 month or in the period of the same hospitalization after low cardiac output or ventricular arrhythmias, or occurring after reoperation or a death of unknown etiology. To further assess the influence of diagnosis on mortality, the patients were broadly divided into two groups. The first group included patients with a future two-ventricle repair and the second group consisted of patients with univentricular physiology. Risk factors for early mortality were analyzed using multivariate analysis. The influences of age, weight, and diagnosis, as well as the type of band (APAB or CPAB) on the mortality rate was analyzed.
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Results |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Early reoperation was required in 17 patients (18.7%) in CPAB group for band tightening (n = 9) and band loosening (n = 8). Three patients in this group required up to four reoperations for achieving adequate band gradients. Two reoperations occurred in the APAB group: one to drain a pericardial effusion and another for a technical error that had produced band loosening. At reoperation, rebanding was performed. This difference in the number of reoperations in the two groups was statistically significant (p = 0.014).
Another difference was in the postoperative inotrope requirement. All patients in CPAB group were either administered or required inotropes to adjust to the altered physiology after PAB. In the APAB group, inotropes were not used electively but were required only in 12 patients (21%) in the ICU who were preoperatively on mechanical ventilation or those who were in intractable congestive heart failure. In other patients in this group, elective inotropes were not used. The other variables, such as the ICU and hospital stay, duration of mechanical ventilation and the final band gradients, were similar in both groups.
Acute events were not uncommon in either group. In CPAB group, 37 acute adverse events occurred, consisting of 14 episodes of sudden cardiorespiratory compromise, out of which 7 patients were not revived; six episodes of sudden ventricular fibrillation, out of which 2 were revived; 10 instances of sudden respiratory arrest requiring emergency endotracheal intubation and band loosening; and seven episodes of transient bradycardia and hemodynamic deterioration requiring optimizations of inotropes. In contrast, only 14 such events occurred in the APAB group, of which 6 patients had cardiorespiratory arrest that responded to removal of the clip used for tightening without reoperation and no patients died. The other 8 patients required optimization of inotropes for bradycardia and altered hemodynamics. One patient required drainage of pericardial effusion and another patient required rebanding because of technical error that occurred when the clip holding the threads together slipped.
Patient age, weight, and the diagnosis did not have any effect on early deaths.
In the latter part of our experience with APAB, we performed this procedure in 5 sick infants with severe degrees of congestive heart failure. Three patients were on prolonged tracheostomy and mechanical ventilatory support and 2 had blood cultures that were positive for acute infective endocarditis with congestive heart failure. All these patients had gradual adjustments of band gradient after APAB and recovered, although the ventilation times were longer and they required inotropic support due to their morbid condition. One patient had an uneventful definitive operation.
All patients were followed up for a mean 22.8 ± 18.6 months (range, 4 to 72 months). There was significant PA distortion in 8 patients in the CPAB group and band migration in another 4. This was not observed in the APAB group. Follow-up computed tomography angiograms in 6 patients in the APAB group ruled out any kinking/tenting of the PA towards the sternum. To date, 8 patients in the CPAB group and 5 in the APAB group have undergone definitive operation. The nature of the reoperations was similar in both groups. Adequate band gradients as desired were encountered in both the groups.
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Determination of optimal band tightness is often difficult, because even minor changes in the diameter of the PA have a large impact on the pulmonary blood flow and the gradient across the PAB [6]. This is further complicated by the fact that during PAB, the patient is on mechanical ventilation under general anesthesia with the chest open [20]. Within the first few hours or days after operation, there are significant alterations in heart rate and contractility, PaO 2 and PaCO 2, acid-base status, hematocrit, and balance between systemic and pulmonary vascular resistance, and these factors compound the effect of a fixed PAB [21]. A loose PAB defeats the very purpose of the operation, whereas a tight PAB can seriously compromise the cardiac output and lead to sudden hemodynamic deterioration with cardiorespiratory compromise.
In children with functionally univentricular hearts, an age-related variability of the ventricular adaptive response is often present, particularly if they require an associated surgical procedure such as repair of coarctation of aorta or atrial septectomy [21, 22]. Progressive tightening over a period of time is very important in older patients with single-ventricle physiology and severe pulmonary hypertension. In these patients, elevated pulmonary vascular resistance does not allow shift to an immediate low level of distal PA pressures. As a result of all these problems, repeated surgical procedures are required to achieve the desired band diameter. Most of these patients require prolonged mechanical ventilatory and inotropic support, and their ICU stay is prolonged.
The need for the development of an APAB arose because of these problems of the continuously variable clinical requirements requiring changes in the band width and the inability of the fixed band to fulfill these. In the 10-year period between 1992 and 2001, more than 16 different techniques of APAB were reported [6,12–15], the latest addition being the flow watch pneumatic device developed by Bonnet and colleagues [16]. These devices are effective but are expensive, require specialized equipment, and have not gained widespread acceptance due to unreliability and lack of reproducibility of adjustments.
We were thus led to develop our own method of APAB, which was reported earlier in a small subset of patients. We addressed the detailed technical aspects, advantages, and concerns of this APAB system in our prior publication [17]. The most important advantages have been that it is simple and inexpensive, no specialized equipment is required, and band tightening is very gradual and under normal physiologic conditions. Our results have demonstrated a significant reduction in early deaths, need for reoperation, inotropic support, and early acute adverse events, without compromising on the degree of desired gradients. Because similar anesthesia techniques and postoperative management protocols were used in the two groups, it is unlikely that these differences could have led to changes in outcomes in the two groups.
This study is a retrospective review of two different types of approaches to PAB in a particular time frame. The patients were not randomized to either of the groups, and the choice of the method of PAB was by surgeon preference in the early part of the experience. However, lately our results have prompted us to move from CPAB to APAB. Given the ease of APAB and better outcomes with our method and with that of others worldwide, it may not be ethically justifiable to conduct a prospective randomized clinical trial comparing CPAB with APAB. Patients with atrioventricular septal defects may have a stormier postoperative course after PAB, and more of these patients were in the CPAB group. However, the differences in numbers between the two groups were not statistically significant. With our current results we feel that these patients may actually have a more predictable course with the use of APAB.
The two groups of patients belong to two different time frames, which may alter the results. These patients all belong to the same decade; however, and as pointed out earlier, we now have more predictable outcomes with APAB compared with CPAB, despite the change of the surgical era, because the results of CPAB still continue to be unpredictable worldwide [11].
In conclusion, encouraged by change in outcomes with the use of APAB, patients requiring PAB are now offered APAB, and we are now able to achieve better outcomes in even the most unsuitable patients in poor general condition.
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