(Circulation. 1995;92:279-286.)
© 1995 American Heart Association, Inc.
Articles |
Influence of Competitive Pulmonary Blood Flow on the Bidirectional Superior Cavopulmonary Shunt
A Multi-Institutional Study
From the Divisions of Pediatric Cardiology and Cardiothoracic Surgery, Wessex Cardiothoracic Centre, Southampton, England; the British Columbia Children's Hospital, Vancouver, Canada; and the Kardiocentrum, Prague, Czech Republic.
Correspondence to Dr S.A. Webber, Division of Cardiology, Children's Hospital of Pittsburgh, 3705 5th Ave, Pittsburgh, PA 15213.
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Abstract |
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Background It is common practice to interrupt all alternative sources of pulmonary blood flow ("competitive flow") at the time of a bidirectional superior cavopulmonary anastomosis (BCPA), although the merits of this have not been systematically studied.
Methods and Results We reviewed the early and medium-term clinical and hemodynamic findings in 108 consecutive patients 3 weeks to 25 years old (median, 1.9 years) undergoing BCPA at one of three institutions. Preoperatively, pulmonary blood flow was dependent on antegrade ventricular flow (n=50), systemic-to-pulmonary shunts (n=33), or mixed sources (n=25). Postoperatively, competitive sources of pulmonary blood flow were left patent in 43 of 108 patients (40%). There were four early (3.7%) and four late deaths, none related to persistence of competitive flow. After BCPA, patients with competitive flow had significantly higher systemic oxygen saturations at 1 hour (85% versus 79%), 24 hours (84% versus 78%), and at hospital discharge (84% versus 78%) and required a shorter period of artificial ventilation (median, 9 versus 24 hours) and intensive care (median, 2 versus 4 days). Oxygen saturations at late follow-up (median, 2.8 years; range, 1 to 7) did not differ (83% versus 82%). No patient developed pulmonary arteriovenous malformations.
Conclusions Competitive flow is well tolerated in the short and medium term after BCPA, and early postoperative systemic oxygen saturations are improved. The long-term influence of competitive flow on pulmonary arterial growth, arteriovenous malformation development, and ventricular function warrants investigation.
Key Words: blood flow • lung • shunts • anastomosis
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Introduction |
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TopAbstractIntroductionMethods Results Discussion References |
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The BCPA is being used with increasing frequency as a palliation for patients with cyanotic congenital heart disease.1 2 3 4 5 6 7 8 9 10 11 12 13 In most centers, the procedure is performed via a median sternotomy, and all alternative sources of pulmonary blood flow are ligated.14 The need for this approach has not been established, and there are potential advantages to leaving pulsatile sources of "competitive" pulmonary blood flow after BCPA.3 7 15 16 17
The earliest clinical applications of BCPA date back to the late 1960s,1 3 when the procedure was performed via a right thoracotomy without ligation of alternative sources of pulmonary blood flow. Recent follow-up3 of the patients operated on by Abrams (since 1967) revealed excellent long-term palliation in most patients, without complications due to the presence of competitive sources of pulmonary blood flow. These observations prompted us to systematically examine the influence of competitive flow on the early and medium-term clinical and hemodynamic results of BCPA.
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Methods |
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TopAbstractIntroductionMethods Results Discussion References |
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Patients
We retrospectively reviewed clinical and hemodynamic data on all 108 patients (63 male) undergoing BCPA at one of three institutions (Wessex Cardiothoracic Centre; British Columbia Children's Hospital, Vancouver; and Kardiocentrum, Prague) up until the end of August 1993. The first procedures were performed in August 1987. Patients with azygous or hemiazygous continuation of the inferior vena cava were excluded, as was one child in whom BCPA was performed during takedown of a Fontan circulation. In almost every case, cardiac anatomy was considered unsuitable for biventricular repair. Three children with pulmonary atresia and intact ventricular septum were considered to be possible candidates for so-called "one and one-half" ventricle repair.13 17 One infant with double-outlet right ventricle, pulmonary stenosis, and noncommitted ventricular septal defect also had unfavorable coronary artery distribution and was considered to be at excessively high risk for attempts at early biventricular repair. Diagnoses included double-inlet ventricle with usual or mirror-image atrial arrangement (n=46, 42%), tricuspid atresia (n=18, 17%), complex heart disease with isomeric atrial appendages (n=12, 11%), and pulmonary atresia with intact ventricular septum (n=11, 10%). In 33 patients (31%), BCPA was the primary palliative surgical procedure. The remaining patients had undergone prior palliative procedures: systemic-to-pulmonary shunt (n=54), pulmonary artery banding (n=10), coarctation repair and pulmonary artery banding (n=9), and atrial septectomy (n=2). Before BCPA, pulmonary blood flow was from the following sources: antegrade from the ventricle(s) (n=50, 47%), systemic-to-pulmonary shunts (n=30, 28%), arterial duct (n=3, 2%), or mixed sources (n=25, 23%).
Median age at BCPA was 23 months (range, 3 weeks to 25 years), and median weight was 10 kg (range, 4 to 68 kg). Twelve patients (11%) were <6 months old at the time of BCPA, and 35 (32%) were <1 year. Mean preoperative systemic arterial saturation was 74±10% (mean±SD), but with a wide range (30% to 92%). Preoperative saturations were higher in the group in whom all sources of competitive flow were tied at the time of BCPA (77% versus 69%; P=.0001). This reflected the tendency to avoid leaving competitive flow in the small group of patients with preoperative evidence of high pulmonary blood flow. For the most part, the decision to leave competitive flow was based on institutional protocol or the individual surgeon's preference and not on morphological or hemodynamic parameters. In no case was a preoperative or intraoperative decision to leave competitive flow based on concern about elevation of pulmonary vascular resistance or inadequate oxygenation during weaning from cardiopulmonary bypass.
Patients have been followed for a median of 2.8
years (1 to 7 years).
No patient was lost at follow-up. Postoperative cardiac
catheterization was performed in 41 patients, 1 week to
7 years after BCPA (median, 2 years). All patients in Southampton
underwent routine cardiac catheterization 
6 months
after surgery. In Vancouver and Prague, cardiac
catheterization was performed when clinical progress
was unsatisfactory or before Fontan repair. Four children underwent
early catheterization within 3 months of BCPA because
of concerns about possible excessive competitive flow (3 patients) or
inadequacy of the cavopulmonary anastomosis (1
patient).
Systemic arterial oxygen saturations before surgery, at discharge, and at latest follow-up were all recorded in room air. Whenever possible, readings obtained by pulse oximetry in the resting state were recorded in preference to arterial oxygen saturations obtained during cardiac catheterization. Measurements of systemic oxygen saturation at 1 and 24 hours after surgery were usually performed with the patient receiving supplemental oxygen.
Surgical Technique
At British Columbia Children's
Hospital (n=34), all BCPA
procedures were performed via median sternotomy using a single right
atrial cannula and a brief period of deep hypothermic circulatory
arrest to avoid placement of a high SVC cannula. An end-to-side
anastomosis was performed, and alternative sources of pulmonary
blood flow were always ligated. In Southampton (n=25) and Prague
(n=49), the decision to leave competitive sources of pulmonary
blood flow was usually determined by the policy of the individual
surgeon performing the procedure. In 16 patients without
pulmonary artery distortion or the need for additional surgical
procedures mandating a median sternotomy, BCPA was performed via a
posterolateral thoracotomy (right, 15; left, 1). In all 16 patients, no
sources of competitive flow were ligated at the time of BCPA. In the
remaining 58 patients operated on in Southampton or Prague, a median
sternotomy was used and BCPA was constructed under moderate or deep
hypothermia and cardiopulmonary bypass or circulatory
arrest, depending on individual anatomic considerations. In 27 of these
58 patients (47%), one or more sources of competitive flow was left
patent. Therefore, 43 of 108 patients (40%) had competitive flow after
BCPA (Table 1
).
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Additional surgical procedures were performed in 56 patients (52%). These included atrial septectomy (n=20), pulmonary arterioplasty (n=13), Damus-Kaye-Stansel procedure (n=10), resection of subaortic stenosis (n=4), repair of recoarctation or hypoplastic aortic arch (n=4), repair of anomalous pulmonary venous return (n=3), and modified arterial switch (n=3). Additional procedures were performed more commonly in patients without competitive flow (43 of 65, 66%) than in those with competitive flow (13 of 43, 30%; P=.0003). Thirteen patients had an additional left-sided SVC without a communicating innominate vein. Nine of these had an additional left-sided BCPA. Two patients had a diminutive right or left caval vein that was ligated at the time of BCPA. The remaining two patients with bilateral caval veins underwent only right-sided BCPA.
Data Analysis
Data are expressed as mean±SD. Since
many variables did not
approximate to a normal distribution, medians and ranges are given
where appropriate. A two-tailed Mann-Whitney U test was
used to compare most outcome measures between patient groups. A
2 test was used to compare the frequency of
prolonged effusions and "SVC syndrome" between patients with and
without competitive flow. A value of P<.05 was considered
statistically significant. The relationships between various outcome
measures and age at BCPA and length of follow-up were explored by
simple linear regression. The relationships between various independent
variables and the principal outcome measures were investigated by
multiple linear regression with a forward stepwise analysis
(GB-Stat, Dynamic Microsystems Inc).
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Results |
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Early Mortality
There were four early deaths (3.7%). None of the deaths were directly related to the presence of competitive flow (present in three of four patients). A 10-year-old child with isomerism of the right atrial appendages and Wolff-Parkinson-White syndrome had simultaneous repair of anomalous pulmonary venous connection (to the SVC). Death occurred due to intractable tachyarrhythmias on day 7 after surgery. A 3-month-old infant with double-inlet left ventricle, discordant ventriculoarterial connection, restrictive ventricular septal defect, and hypoplastic aorta died of low cardiac output after relief of subaortic stenosis, aortic arch reconstruction, and BCPA. A 3-year-old with pulmonary stenosis and right ventricular hypoplasia had a smooth early postoperative course but died unexpectedly after an aspiration episode on day 7 after surgery. The final death occurred in a 3-month-old infant with tricuspid atresia. Early after surgery, he developed abdominal distension and low saturations (70%). Cardiac catheterization revealed a stenosis of the BCPA. Profound hypoxia was prevented because of antegrade flow from the right ventricle, which had not been ligated. A central systemic-to-pulmonary shunt was performed through a median sternotomy, and the BCPA was taken down. Septicemia ensued, and the patient died on day 10 after surgery. Autopsy revealed peritonitis due to unexplained perforation of the proximal descending colon.
Morbidity
Serious or potentially serious complications were
noted in 15
(14%) of the 104 early survivors. These were bleeding requiring
reoperation (n=4), tachyarrhythmias (n=5), complete heart
block during ventricular septal defect enlargement (n=1),
bilateral phrenic nerve paresis (n=1), low cardiac output state with
multisystem failure (n=4), mediastinitis (n=2), transient
cortical
blindness (n=1), mild developmental delay (n=2), and SVC
thrombosis
requiring intracaval streptokinase therapy (n=1). Several patients (all
with low output state) experienced more than one complication. Major
complications were seen almost exclusively in patients undergoing BCPA
with additional major procedures. Long-term morbidity was seen in
only 3 patients: complete heart block in 1 and mild developmental delay
in 2 (one definitely related to surgery). Eleven of the 15 patients
(73%) with major complications had ligation of all sources of
competitive flow at the time of BCPA. With the exception of one neonate
with severe SVC syndrome (see below), major complications could not be
attributed to the presence of competitive flow.
Influence of Competitive Flow on the Early Postoperative
Course
A comparison of the perioperative course between
patients with and without competitive flow is summarized in Table
2. Patients with competitive flow had significantly
higher systemic oxygen saturations at 1 hour and at 24 hours after
surgery, as well as at hospital discharge. They also required a shorter
period of artificial ventilation (median, 9 versus 24 hours) and had a
shorter stay in the intensive care unit (median, 2 versus 4 days).
Timing of hospital discharge did not differ between the groups. The
favorable effect of competitive flow on the early postoperative course
was confirmed in the multivariate analysis
(Table 3). Prolonged pericardial or pleural effusions
(defined as need for pericardial or pleural drainage after day 5 after
surgery) occurred in 13 patients, 8 with and 5 without competitive flow
(P=.088). Severe or prolonged upper-body edema was noted
in 7 patients, 4 with and 3 without competitive flow
(P=.333).
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Since fewer patients with competitive flow
underwent concomitant
additional surgical procedures, it was thought that this might explain
the improved early oxygen saturations and slightly smoother
postoperative course in patients with competitive flow. Therefore, the
univariate analyses were repeated for the 52
patients who had not undergone an additional surgical procedure (Table
2
). The findings were almost identical to those for the whole
population, suggesting a genuine early beneficial effect of competitive
flow. Multivariate analysis suggested that the
need for concomitant additional surgical procedures did exert an
independent effect on the length of intensive care stay and oxygen
saturations immediately after surgery and at hospital discharge. The
association between additional surgical procedures and lower systemic
oxygen saturations, however, was weaker than the effect of removal of
sources of competitive flow (Table 3).
Excessive Competitive Flow
Three of 43 patients (7%) were
subsequently considered to have
excessive competitive flow. A 3-week-old infant underwent BCPA via
a right thoracotomy, leaving competitive flow both from the right
ventricular outflow and from a left-sided
arterial duct. Saturations before surgery had been labile,
ranging from 60% to >80%. In retrospect, lability of both the
pulmonary vascular bed and right ventricular
outflow obstruction, rather than constriction of the
arterial duct, was probably responsible for the marked
swings in arterial saturations before surgery. A severe
"SVC syndrome" developed in the immediate postoperative period,
and ligation of what proved to be a large patent arterial
duct was performed on day 4 after surgery. Nine months later, this
child remains well without medication and with resting
arterial oxygen saturation of 82% and mean
pulmonary artery pressure of 14 mm Hg. Two other children
developed less acute symptoms due to excessive competitive flow. An
8-month-old infant with pulmonary atresia and intact
ventricular septum had persistent upper body edema
postoperatively and underwent ligation of a left Blalock-Taussig shunt
10 weeks after BCPA. This resulted in resolution of symptoms, and she
remains asymptomatic. A 6-year-old girl with
isomerism of the right atrial appendages, pulmonary and
subpulmonary stenosis, and moderate
regurgitation of a common AV valve developed a chronic
left pleural effusion after BCPA. Postoperatively, competitive
pulmonary blood flow was from the native pulmonary
outflow tract and from a right modified Blalock-Taussig shunt. Mean
pulmonary artery pressure was 11 mm Hg after weaning from
cardiopulmonary bypass but was 27 mm Hg at postoperative
catheterization 3 months later. Successful balloon
occlusion of the Blalock-Taussig shunt resulted in a fall of mean
pulmonary artery pressure to 17 mm Hg and resolution of the
effusion.
Sternotomy Versus Thoracotomy Technique
To compare the
perioperative courses of the two
surgical techniques, the 16 children who underwent thoracotomy were
compared with the 14 who underwent sternotomy without additional
surgical procedures and in whom competitive flow was not tied. The two
groups were of similar age and weight and had comparable preoperative
saturations. The group who underwent sternotomy had higher saturations
at 1 hour (90% versus 83%, P=.035) but had almost
identical saturations at 24 hours (sternotomy, 85% versus thoracotomy,
84%), at discharge (83% versus 85%), and at late follow-up (83%
versus 82%). Patients who underwent sternotomy were ventilated for
slightly longer (median, 20 versus 3 hours; P=.012), but
hospital stay was unaffected. Pulmonary artery pressure at late
follow-up did not differ between the groups (14±3 mm Hg).
Multivariate analysis suggested no independent
effect of surgical approach on any of the principal outcome measures
(Table 3).
Influence of Age at BCPA on Early and Late Results
Perioperative course and late saturations and
hemodynamics for patients who underwent BCPA before or
after 1 year of age are shown in Table 4. Late
saturations and pulmonary artery pressures did not differ
between the two groups, although early oxygenation was
slightly better in the older children. The results of simple linear
regression between various outcome variables and age at BCPA are
also shown (Table 4). These show a weak trend toward higher
early
postoperative oxygen saturations in older patients but no association
between age at BCPA and late systemic saturations (Fig 1).
Multivariate analysis
suggested an independent beneficial effect of older age on higher
postoperative saturations (at 24 hours and at discharge). The
association was weaker than that for persistence of competitive flow
(Table 3).
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Late Outcome
There were four late deaths (3.8%), two
occurring early after
further surgical procedures. One child died of uncontrollable
hemorrhage after total cavopulmonary connection.
Three other deaths all occurred in patients with isomerism of the right
atrial appendages and complex heart disease. One child developed
progressive cyanosis and upper body edema after BCPA due to the
development of pulmonary venous obstruction at the site of
total anomalous pulmonary venous connection to the low SVC.
Death occurred 4 days after correction of total anomalous
pulmonary venous connection due to arrhythmias and low
cardiac output. An 18-month-old died of cardiac failure due to the
progression of common AV valve regurgitation 7 months
after BCPA. The final child also developed severe
regurgitation of a common AV valve. This was
successfully replaced 8 months after BCPA, but the patient died
unexpectedly at home 6 months later during an acute
"flu-like" illness.
Seven additional children had subsequent surgical procedures, each consisting of baffling of inferior caval return to the pulmonary arteries (ie, completion of TCPC). There were no deaths, but one child required early takedown (to BCPA) because of massive postoperative effusions. No child other than the patients undergoing TCPC had late procedures to augment pulmonary blood flow. No child required early or late takedown of the BCPA.
Saturation
data at latest follow-up and late pulmonary
artery pressures measured at follow-up cardiac
catheterization (n=41) are shown in Table 2 and Fig
1.
Late saturations did not differ between patients with and without
competitive flow. Mean pulmonary artery pressure was slightly
higher in patients with competitive flow (15 versus 12 mm Hg;
P=.033). This difference was not found in the subgroup of
BCPA without additional surgical procedures. Systemic oxygen
saturations immediately after completion of surgery correlated only
weakly with saturations at late follow-up (r=.227;
P=.027) (Fig 2). There was no correlation
between the length of follow-up and systemic saturations
(r=.106; P=.31) (Fig 3). Among
the
41 patients who underwent follow-up
catheterization, only the patient who died early with
unexplained peritonitis had hemodynamic or angiographic
evidence of cavopulmonary anastomotic narrowing. No
pulmonary arteriovenous malformations were identified by
angiography. Five patients developed prominent venovenous collaterals
between the superior and inferior caval veins. None have
developed progressive cyanosis, and embolization has not been
performed.
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Inadequate Palliation (Saturations <75%)
Among the 104
operative survivors, 4 (including 1 with competitive
flow) had persistent resting saturations <75%. In 3 patients, the
cause was apparent (poor ventricular function, right BCPA
only in presence of large left SVC, severe AV valve
regurgitation), but all 3 showed
symptomatic improvement (rise in saturations or improvement
in ventricular function and exercise tolerance) after BCPA.
Four other patients (including 1 with competitive flow) developed
progressive cyanosis (saturations <75%) late (>3 months) after BCPA,
2 due to progression of common AV valve regurgitation
and 1 due to development of pulmonary venous obstruction (see
above). No specific cause was identified in the remaining patient.
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Discussion |
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BCPA has gained wide popularity in recent years as a palliation for cyanotic heart disease.1 2 3 4 5 6 7 8 9 10 11 12 13 It is most often performed as an interim palliation for patients considered candidates for Fontan-type repair.5 11 It is widely recognized that BCPA can provide adequate pulmonary blood flow and systemic arterial oxygen saturations in appropriately selected patients.3 4 5 6 7 8 9 10 11 12 With rare exceptions,5 10 11 most reports of BCPA have comprised fewer than 30 patients, and median follow-up exceeds 5 years in only one study.3 Many important questions remain unanswered: At how young an age can the procedure be performed? What factors predict a good clinical result? What surgical techniques should be used? What is the long-term outcome with reference to systemic saturations, ventricular performance, exercise tolerance, pulmonary arterial growth, risk of PAVM, and suitability for and timing of subsequent Fontan-type repair?
In the present study, we have paid particular attention to the influence of competitive sources of pulmonary blood flow on the early and medium-term results of BCPA. To the best of our knowledge, this collaborative study represents one of the largest published series of patients undergoing BCPA. This has enabled us to also address some of the above issues, particularly early morbidity and mortality and factors influencing early and medium-term efficacy of BCPA.
Morbidity and Mortality
The reported mortality for BCPA
ranges from 0% to
33%.1 2 3 4 5 6 7 8 9 10 11 12
Interpretation of mortality data is complicated
by the differing eras of surgery, patient populations, and surgical
techniques. The mortality in the present series (3.7%) is within
the range found in the three prior reports exceeding 30 patients (0%
to 8%).5 10 11 It is noteworthy that one
of four early
deaths and three of four late deaths in this report were in patients
with isomerism of the right atrial appendages. This emphasizes the
challenge of managing this difficult group of patients. Poor results
from BCPA in these patients was also noted by Albanese and
colleagues.9
Important morbidity was also seen in 14% of our patients, especially when additional surgical procedures were required. Fortunately, these complications were rarely permanent. No specific strategies for reducing this morbidity are apparent from this review.
Efficacy of BCPA as Palliation for Complex Congenital Heart
Disease
Systemic oxygen saturations in the present study rose from a
median of 75% preoperatively to 83% at latest follow-up. These
findings are similar to those in other
studies.4 7 10 12
Inadequate relief of cyanosis (saturations <75%) was found in only
4% of patients, in contrast to 13% reported by Bridges et
al.5 This probably reflects differing patient populations
and the reluctance to attempt BCPA in patients with significant
elevation of pulmonary vascular resistance in our three
institutions. Although efficacy of BCPA is most commonly assessed by
the increase in resting systemic oxygen saturations, the extent of
desaturation during exercise may be an important determinant of
exercise tolerance after BCPA. This information is difficult to obtain
in young children, and we have not yet collected data on exercise
performance in this group of patients.
Age at BCPA did not influence late saturations or hemodynamics in the present study. Gross and colleagues18 reported that older/larger patients are more likely to have lower systemic arterial oxygen saturations after BCPA and that this might reflect a decreasing ratio of upper- to lower-body systemic blood flow with age. We have been unable to verify this observation in this large cohort, and we believe that BCPA can provide effective palliation for carefully selected patients of almost any age, including small infants (and possibly even neonates) and young adults.
Postoperative improvements in systemic oxygen saturations were sustained during the medium-term follow-up in almost all patients. We also noted that the small group of children with inadequate oxygenation after BCPA usually had clear anatomic or hemodynamic explanations, such as pulmonary venous obstruction or progression of AV valve regurgitation or ventricular dysfunction. Continued follow-up is required to see whether the improvements in oxygen saturations after BCPA are maintained long-term.
In many centers, it is customary to perform completion of TCPC at an arbitrary age or interval after BCPA. The logic for this strategy is mainly the empirical assumption that it is best, whenever possible, to completely separate the pulmonary and systemic circulations. Although this will increase systemic oxygenation and decrease the risk of paradoxical emboli and cerebral abscess, other advantages are less certain. It is unknown whether late survival, exercise tolerance, or quality of life will be improved. Completion of the TCPC will carry a small but important risk of death or major complication. Limited cardiac output reserve may replace desaturation as a limiting factor determining exercise performance. Arrhythmias are likely to be exacerbated due to the additional intra-atrial surgery.19 Research is urgently required to establish the short- and long-term effects of elective conversion of patients with BCPA or hemi-Fontan to TCPC.
Influence of Competitive Pulmonary Blood Flow on Early and
Late Outcome of BCPA
We have demonstrated that competitive sources of
pulmonary
blood flow are well tolerated after BCPA and in fact appear to confer a
small advantage in terms of early postoperative
oxygenation and period of intensive care support. Late
saturations did not differ, and there was only a minimal increase in
late pulmonary artery pressure in the competitive flow group.
This differential is likely to decrease with time as alternative
sources of pulmonary blood flow gradually diminish. Several
prior reports of BCPA have included patients with postoperative
competitive flow. This includes a number of series in which a
thoracotomy approach has been used either
exclusively1 3
or in a proportion of
cases,2 6 7 10 as well as
occasional
reports of competitive flow being left after BCPA performed via median
sternotomy.4 7 9 None of these studies
systematically
compared outcome in patients with and without competitive flow. Only
two prior reports focused on the hemodynamic and
clinical effects of BCPA associated with alternative sources of
pulsatile pulmonary blood flow.7 13 Muster and
colleagues13 demonstrated in a small group of patients
that BCPA may be successfully used to accomplish so-called "one
and one-half ventricle repair"17 in the setting of
moderate right ventricular hypoplasia. Kobayashi and
colleagues7 described the hemodynamic
findings and clinical outcome of 10 high-risk Fontan candidates who
underwent BCPA without ligation of competitive pulmonary blood
flow. Arterial oxygen saturation and pulmonary
artery pressures at follow-up were very similar to those reported
in this study.
Several authors have drawn attention to the potential benefits of leaving some pulsatile flow in the pulmonary arteries after BCPA.3 7 13 17 Kobayashi and colleagues7 emphasized the possible beneficial effects of pulsatile flow in preventing the late development of PAVMs. To date, we have not observed PAVMs in any of the 104 early survivors of BCPA, irrespective of whether competitive flow was present. Competitive flow also ensures that some hepatic venous return reaches the lungs. If a "hepatic factor"17 is important for the prevention of PAVMs, then this might represent another advantage of BCPA with competitive pulmonary blood flow. A further potential benefit of pulsatile flow is its association with reduction in vascular resistance.15 16 21 It is not known whether this has practical relevance for patients with borderline acceptable pulmonary vascular resistance undergoing BCPA.
A final potential advantage of pulsatile competitive flow is that it may enhance pulmonary arterial growth. A recent report has raised concerns about the adequacy of pulmonary arterial growth in some patients after BCPA.22 We suspect that pulsatile flow may enhance pulmonary artery growth, and this may be particularly important if BCPA is performed in infants with relatively small pulmonary arteries. We are currently investigating the influence of competitive flow on pulmonary arterial growth after BCPA.
Despite these potential advantages of leaving competitive flow, most centers routinely perform BCPA via median sternotomy with ligation of all alternative sources of pulmonary blood flow.14 This largely reflects concern that leaving pulsatile flow may result in excessively high pulmonary artery pressure and the development of SVC syndrome and chronic effusions. Our data do not support this concern, provided that careful attention is paid to patient selection. Excessive competitive flow was found in only 3 of 43 patients in the present study, and in only 1 of these patients was early takedown of alternative sources of pulmonary blood flow required. Precise criteria for when it is appropriate to leave competitive flow are not yet established. Chang and colleagues12 suggested leaving antegrade flow to the lungs via a stenotic pulmonary outflow tract or from a systemic-to-pulmonary shunt if systemic arterial saturations are <70% in the operating room. Our data have shown, however, that there is only a poor correlation between immediate postoperative saturations and saturations over the coming days and at late follow-up. Saturations in the operating room will therefore be an insensitive guide as to which patients might benefit from pulsatile augmentation of pulmonary blood flow after BCPA. It is also unclear as to how helpful intraoperative hemodynamic measurements will prove to be in this respect. One of our patients requiring late ligation of a Blalock-Taussig shunt had an SVC pressure of only 11 mm Hg after weaning from cardiopulmonary bypass. Albanese and colleagues9 performed ligation of the main pulmonary artery only when mean pulmonary artery pressure rose to >15 mm Hg off cardiopulmonary bypass. Despite this strategy, 2 patients required subsequent ligation of competitive flow, and 1 child required reopening of the main pulmonary artery because of persistent cyanosis. Mazzera and colleagues4 performed ligation of the main pulmonary artery when a pulsatile waveform was noted in the SVC after BCPA. We do not believe that this is a reliable criterion, since we have noted this hemodynamic pattern in a number of patients who have had an excellent clinical and hemodynamic response to surgery. Others have made similar observations.13 We believe that the majority of patients undergoing BCPA for the relief of moderate to severe cyanosis will tolerate competitive flow.
A further argument in favor of ligating all competitive flow is to minimize ventricular volume loading. Berman and Kimball20 demonstrated significant reduction in ventricular size after BCPA when all alternative sources of pulmonary blood flow were ligated. This may help preserve ventricular function and reduce left ventricular mass index. AV valve regurgitation may also be improved.12 It is of interest to note, however, that Kobayashi et al7 demonstrated similar reductions in ventricular size and improvement in AV valve regurgitation in patients after BCPA, with preservation of pulsatile pulmonary blood flow. We therefore doubt that the theoretical consideration of minimizing ventricular volume loading represents a valid contraindication to leaving competitive flow in patients with moderate to severe cyanosis before BCPA. Furthermore, the comparable systemic saturations at late follow-up in patients with and without competitive flow in the present series suggests that there is probably no important additional ventricular volume loading late after BCPA in our patients with competitive flow. This most likely reflects the natural tendency for alternative sources of pulmonary blood flow to diminish over time. We would, however, advocate early postoperative cardiac catheterization when there is any concern about the possibility of excessive pulsatile flow or high pulmonary artery pressure after BCPA.
It is perhaps surprising that so few groups have explored the possibility of BCPA with competitive flow. Both the original animal work by Haller and colleagues23 and the first clinical applications of BCPA (L.D. Abrams and colleagues, 1967; G. Azzolina and colleagues, 1969)1 3 used a thoracotomy approach without ligation of other sources of pulmonary blood flow. Our observations that competitive flow is well tolerated and may actually improve the early postoperative course suggest that consideration should be given to wider application of this technique. The avoidance of sternotomy has the additional advantage of simplifying subsequent completion of the cavopulmonary connection. Even when median sternotomy is indicated for concomitant additional procedures, we believe that the presence of additional sources of pulsatile pulmonary blood flow has several practical and theoretical advantages. Continued follow-up of this large cohort will help confirm or refute the long-term clinical benefits of BCPA with pulsatile competitive pulmonary blood flow.
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References |
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TopAbstractIntroductionMethods Results Discussion References |
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1. Azzolina G, Eufrate S, Pensa P. Tricuspid atresia: experience in surgical management with a modified cavopulmonary anastomosis. Thorax. 1972;27:111-115.
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