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Ann Thorac Surg 2005;80:1597-1603
© 2005 The Society of Thoracic Surgeons
a Department of Cardiology, Children's Hospital, Boston, Massachusetts
b Department of Cardiac Surgery, Children's Hospital, Boston, Massachusetts
c Department of Pediatrics, Harvard Medical School, Boston, Massachusetts
d Department of Surgery, Harvard Medical School, Boston, Massachusetts
Accepted for publication May 9, 2005.
* Address correspondence to Dr McElhinney, Department of Cardiology, Children's Hospital, 300 Longwood Avenue, Boston, MA 02115 (Email: doff.mcelhinney{at}cardio.chboston.org).
| Abstract |
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METHODS: We studied 16 patients with heterotaxy, univentricular congenital heart disease, and azygous continuation of the IVC who underwent incorporation of the HV into the cavopulmonary circuit for treatment of significant PAVMs after a Kawashima procedure.
RESULTS: The median preoperative systemic arterial oxygen saturation (SsaO2) was 76% (65%85%), compared with 89% (85% to 92%) early after BCPA. Among 15 early survivors, the median early postoperative SsaO2was 76% (56%85%). In 11 of the 15 survivors, SsaO2 rose to 90% or greater within a year and remained at 93% or greater at follow-up of 2.8 to 10 years. Four patients had persistent hypoxemia and residual PAVMs at follow-up catheterization 1.5 to 8 years postoperatively; these patients had the most severe hypoxemia prior to HV inclusion, and in 2 the residual PAVMs were unilateral, with HV flow streaming to the contralateral lung, in which PAVMs had resolved.
CONCLUSIONS: Hypoxemia resolved after cavopulmonary incorporation of the HV in the majority of our patients with PAVMs after the Kawashima operation, presumably due to a combination of PAVM resolution and elimination of hepatic venoatrial right-to-left shunting. These findings support the theory that development of PAVMs is facilitated by exclusion of HV effluent from the pulmonary circulation.
| Introduction |
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The cause of PAVMs is unknown. However, there is increasing evidence to support the hypothesis that development of PAVMs is facilitated when an unidentified factor produced in the liver does not reach the pulmonary circulation [10]. In individuals with congenital heart disease, PAVMs develop almost exclusively in circumstances in which hepatic vein (HV) blood does not perfuse the pulmonary circulation before first traversing a systemic capillary bed [15, 8, 10]. PAVMs are also a feature of the hepatopulmonary syndrome that can occur in patients with hepatic cirrhosis [17], and of hereditary hemorrhagic telangiectasia (HHTA) [18]. The "hepatic factor" hypothesis is supported by reports of PAVMs resolving in patients with a BCPA after diversion of HV effluent to the pulmonary arteries (PAs) [11, 14, 1921] or cardiac transplant [22], or after liver transplant in patients with the hepatopulmonary syndrome [23]. Whether such reports are unique cases or the typical response to direction of HV effluent to the pulmonary circulation, however, is unclear, as there has been no systematic investigation of the clinical course after cavopulmonary incorporation of the HV in patients with univentricular heart disease who have developed PAVMs after BCPA.
| Patients and Methods |
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Diagnostic Criteria
Pulmonary arteriovenous malformations were diagnosed when there were the following: (1) rapid pulmonary AV transit (< 3 heart beats) of contrast on proximal PA angiography; (2) a typical reticular or spongy pattern in the peripheral pulmonary vasculature on PA angiography; and (3) for the 13 patients in whom pulmonary venous (PV) blood was sampled, PV desaturation (
92%) in angiographically affected lung segments.
Data Analysis
Within-patient and between-patient data were compared using paired and independent samples t test analyses, respectively. Repeated measures analysis of variance was used to compare serial measurements between groups of patients. Unless otherwise specified, oxygen saturations were measured in room air. Data are expressed as mean ± standard deviation or median (range).
Control Patients
Clinical management and outcomes were reviewed for a control group of patients with heterotaxy, univentricular heart disease, and azygous continuation of an interrupted IVC to the SVC who underwent BCPA and/or total cavopulmonary connection at our center between 1985 and 2001 and did not have PAVMs.
| Results |
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Bidirectional Superior Cavopulmonary Anastomosis
A Kawashima procedure had been performed in all patients (14 at our center and 2 elsewhere) between 1985 and 1999, at a median age of 10 months (4 months to12 years). Nine of 10 patients with bilateral SVCs underwent bilateral BCPA; in 1 patient, a nondominant left SVC was ligated. The median systemic arterial oxygen saturation (SsaO2) early after BCPA was 89% (85% to 92%; Fig 1).
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92%) in at least 1 PV (median 2 PVs desaturated) corresponding with angiographic PAVMs, without correction in 100% oxygen. In the patient with unilateral angiographic PAVMs, there was PV desaturation ipsilateral to the angiographic PAVMs and normally saturated PV blood from the lung without angiographic PAVMs. The SsaO2 at catheterization ranged from 65% to 85% (median 76%; p < 0.001 vs early post-BCPA measurement; Fig 1), and the median hemoglobin level was 18.0 g/dL (15.219.7 g/dL). The patient with the highest SsaO2 (85%) was the only patient with unilateral PAVMs. Eight patients underwent coil embolization of systemic-pulmonary venous collaterals during the same catheterization.
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Early Outcomes
One patient died 26 days after HV incorporation, with severe cyanosis, acute liver failure, low cardiac output secondary to poor ventricular function, and ultimately multiorgan failure. This patient had undergone atrioventricular valve replacement at the time of HV incorporation and pacemaker placement in the early postoperative period for heart block.
In 9 of the 15 survivors, the early postoperative course was notable for severe hypoxemia (SsaO2
65%, usually on supplemental oxygen) lasting at least a week. Five of these 9 patients had a fenestration, while 2 of the 6 patients without severe hypoxemia had a fenestration (p= not significant). Two patients developed hemidiaphragm paralysis, one bilaterally and one on the side of the HV pathway. The median duration of hospitalization after HV incorporation was 10 days (4 to 34 days). The median SsaO2 at the time of hospital discharge was 77% (56% to 90%; p = 0.26 vs preoperative). Two patients were discharged on supplemental oxygen.
Follow-Up
All 15 early survivors were alive at a median cross-sectional follow-up of 6.6 years (2.8 to 10 years). Systemic arterial oxygen saturation rose to greater than 90% between 1 week and 12 months (median 4 months) postoperatively in 11 of the 15 early survivors. At a median follow-up of 6.3 years (2.8 to 10 years), these patients, including one with an open fenestration, maintained stable SsaO2 93% or greater (median 95%). The other 4 patients had persistent hypoxemia, with a SsaO2 from 69% to 79% at most recent follow-up (4.4 to 10 years). Among the entire cohort, SsaO2 was 90 ± 9% at follow-up vs 76 ± 8% in the early postoperative period and 74 ± 7% at preoperative catheterization (p < 0.001). Age, duration between BCPA and diagnosis of PAVMs, and SsaO2after BCPA were similar in these patients and those in whom hypoxemia resolved. However, the 4 patients with persistent hypoxemia had significantly lower SsaO2 both at the time PAVMs were diagnosed and at the time of hospital discharge after HV incorporation. They also had a significantly greater decrease in SsaO2 between BCPA and the diagnosis of PAVMs (p < 0.001; Fig 1). In all 4 of these patients, including both of those with large, angiographically discrete PAVMs preoperatively, and one with a patent conduit fenestration, persistent hypoxemia was documented by cardiac catheterization to be due at least in part to PAVMs.
Follow-Up Catheterization
Follow-up catheterization was performed in 7 patients (13 catheterization procedures), including 3 of the 11 with stable SsaO2 93% or greater and all 4 with persistent hypoxemia. In the 3 catheterized patients with stable SsaO2 93% or greater, there was angiographic resolution of PAVMs at the most recent catheterization and normal PV saturations in the previously affected lung(s). One of these patients had undergone prior catheterization 1 year postoperatively, when the baffle fenestration remained patent and the majority of HV flow was through the fenestration, at which time the PAVMs were still present (Fig 3). The fenestration was closed, and at subsequent catheterization 3 years later the PAVMs had resolved (Fig 3). In all 4 patients with persistent hypoxemia, PAVMs were still present at follow-up catheterization 1.5 to 8 years postoperatively. Two of these patients had large, angiographically discrete PAVMs preoperatively, which were still present at follow-up catheterization (Fig 2). In the other 2, who had bilateral PAVMs prior to HV inclusion, the PAVMs identified at late catheterization were unilateral, with all or most HV flow streaming to the contralateral lung (Fig 3), in which the PAVMs had resolved.
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| Comment |
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There are a number of reasons to believe that increased SsaO2 after HV inclusion was due at least in part to decreased shunting through PAVMs. First, PAVMs and their contribution to preoperative hypoxemia were documented in all patients, and SsaO2 prior to HV incorporation was significantly lower in study patients than a comparable cohort of control patients with a Kawashima procedure who did not have PAVMs. Although SsaO2 typically decreases with age after a BCPA, most likely due to redistribution of systemic blood flow to the lower body [24], the magnitude of this decrement is not commensurate with the severity of hypoxemia observed in our patients. Second, in 3 patients, resolution of PAVMs was documented at catheterization. Third, the majority of patients had SsaO2 93% or greater at follow-up, which is unlikely in the context of significant persistent PAVMs. Fourth, the time course of improved SsaO2 after HV inclusion was inconsistent with the explanation that hypoxemia improved simply because hepatic venoatrial right-to-left shunting was eliminated: early postoperative SsaO2was very low in most patients, improving by the time of hospital discharge to preoperative levels, and only gradually rising above 90% over the next month to year. Elimination of hepatic venoatrial right-to-left shunting alone should have improved hypoxemia immediately after redirection of HV flow, whereas resolution of PAVMs might be expected to occur gradually.
Although hypoxemia resolved after HV inclusion in the majority of our cohort, SsaO2 never normalized in 4 patients with persistent PAVMs at follow-up catheterization. These patients differed from those in whom hypoxemia resolved in several respects: (1) they had the most severe hypoxemia at the time of PAVM diagnosis; (2) 2 of them had large, angiographically discrete PAVMs before HV inclusion; and (3) 2 others had streaming of flow in the HV-PA pathway such that HV blood flowed exclusively or primarily to one lung, in which PAVMs had resolved, while PAVMs persisted in the lung not receiving HV flow. Unilateral streaming of HV-PA flow is an important concern after HV inclusion in patients with heterotaxy and azygous continuation of the IVC. Even if bilateral SVCs are present, the SVC receiving azygous return carries at least 50% of upper body venous return and essentially all lower body and nonsplanchnic abdominal venous return. If this SVC is contralateral to or widely offset from the HV-PA pathway, there is no mechanical impetus for HV effluent to flow to the lung on that side. As investigators have shown using in vitro and computational simulations, flow streaming may be mechanically advantageous in a total cavopulmonary circulation, and offset between the IVC-PA and SVC-PA connections can produce complete or near-complete streaming of HV effluent to the ipsilateral lung [25].
Etiology of PAVMs After a Kawashima Procedure
Patients with the polysplenia form of heterotaxy seem to be more prone to develop PAVMs and to develop them more rapidly after a Kawashima procedure, in which all systemic venous return except HV and coronary venous effluent is to the PA circulation, than patients with other forms of heart disease who undergo BCPA [4, 10, 11, 1316]. Patients with heterotaxy and polysplenia have been reported to develop PAVMs without a Kawashima circulation, but only in the setting of biliary atresia, which is associated with the hepatopulmonary syndrome in its own right [10, 17, 23]. It may be the combination of heterotaxy and a Kawashima circulation that predisposes patients to the formation of PAVMs.
Insights into the pathogenesis of PAVMs in patients with a CPA, particularly those with heterotaxy and a Kawashima circulation, may be offered by the genotypic characterization of HHTA, in which patients develop PAVMs and other vascular anomalies. The majority of patients with HHTA are haploinsufficient for 1 of 2 functionally related genes (endoglin and ALK-1) that encode transforming growth factor (TGF)-ß receptor subunits involved in endothelial TGF-ß signaling, which has been implicated in AV differentiation and angiogenic homeostasis [18]. Of note, most of the genes involved in left-right axis determination, and implicated in human heterotaxy syndromes, also encode mediators of TGF-ß family signal transduction [26, 27]. Patients with heterotaxy, like those with HHTA, may be predisposed to form PAVMs by virtue of disruptions of TGF-ß signaling, although this hypothesis has yet to be tested.
Several investigators [8, 28, 29] have developed animal models to study pulmonary vascular changes, particularly PAVM formation, in the setting of CPA. Studies from these labs have characterized some of the cellular and molecular effects of CPA, and will hopefully lead to an improved understanding of the causes of PAVMs in this setting.
Conclusions
Hypoxemia resolved after cavopulmonary incorporation of the HV in the majority of our patients with polysplenia syndrome and PAVMs after a Kawashima procedure, presumably due to a combination of resolution of PAVMs and elimination of hepatic venoatrial right-to-left shunting. In a subset of patients with the most profound hypoxemia at the time of PAVM diagnosis and either anatomically advanced PAVMs or postoperative streaming of HV flow to a single lung, PAVMs persisted, typically in the lung that received little or no HV effluent. Of note, creation of an ipsilateral brachial AV fistula in the 2 patients with unilateral HV streaming and persistent PAVMs in the contralateral lung did not result in resolution of PAVMs, in contrast to our experience in patients with unidirectional CPA [30]. In patients with HV streaming, no HV blood reaches the systemic arterial circulation (and hence the brachial AV fistula) without first passing through the lung without PAVMs. These observations support the hypothesis that development of PAVMs is facilitated by exclusion from the pulmonary circulation of a hepatically produced-modified factor that is inactivated-consumed during passage across any capillary bed, and that must be delivered to the affected lung in order for PAVMs to regress.
Although the duration of time with a Kawashima circulation did not predict resolution of hypoxemia after HV inclusion, patients with more profound hypoxemia were less likely to benefit from cavopulmonary incorporation of HV flow. Accordingly, we recommend a high index of suspicion for PAVMs, and Fontan completion within 1 to 2 years, in patients with polysplenia and an interrupted IVC who have undergone a Kawashima procedure. Fenestration of the HV pathway may prevent sufficient HV flow from reaching the pulmonary circulation, and should be limited to patients with a specific indication. Alternatively, total cavopulmonary connection without intermediate BCPA may decrease the likelihood of PAVMs in selected patients with balanced pulmonary blood flow. Also, 2 of 4 patients with persistent hypoxemia and PAVMs after HV inclusion had unilateral streaming of HV-PA flow. Thus, approaches that are less likely to be complicated by streaming [22] may be advisable, especially in patients in whom significant SVC-HV offset is likely with unilateral intraatrial or extracardiac redirection of HV return. In patients with unilateral HV streaming, an upper extremity systemic AV fistula is ineffective for treating PAVMs, and should not be performed. Large PAVMs may not resolve after inclusion of hepatic flow, and should be embolized at catheterization prior to HV inclusion.
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Once the article selected for discussion is published in the online version of The Annals, we will post a notice on the CTSNet home page ( http://www.ctsnet.org ) with a FREE LINK to the full-text article. Readers wishing to comment can post their own commentary in the discussion forum for that article, which will be informally moderated by The Annals Internet Editor. We encourage all surgeons to participate in this interesting exchange and to avail themselves of the other valuable features of the CTSNet Discussion Forum and Web site.
For November, the article chosen for discussion under the Pediatric Cardiac Dilemma Section of the Discussion forum is:
Outcomes After the Stage I Reconstruction Comparing the Right Ventricular to Pulmonary Artery Conduit With the Modified Blalock Taussig Shunt
Sarah Tabbutt, MD, PhD, Troy E. Dominguez, MD, Chitra Ravishankar, MD, Bradley S. Marino, MD, Peter J. Gruber, MD, PhD, Gil Wernovsky, MD, J. William Gaynor, MD, Susan C. Nicolson, MD, and Thomas L. Spray, MD
Tom R. Karl, MD
The Annals Internet Editor
UCSF Children's Hospital
Pediatric Cardiac Surgical Unit
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San Francisco, CA 94143-0118
Phone: (415) 476-3501
Fax: (212) 202-3622
e-mail: mailto:karlt{at}surgery.ucsf.edu
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