Ann Thorac Surg 2007;84:2112-2114. doi:10.1016/j.athoracsur.2007.06.084
© 2007 The Society of Thoracic Surgeons
Case Reports
Staged Hybrid Left Pulmonary Artery Rehabilitation in Post-Fontan Left Pulmonary Artery Hypoplasia
John W. Scotta,
John M. Karamichalis, MDb,
Frank Ingc,
Lance Shiraid,
David Bichell, MDb,*
a Vanderbilt University School of Medicine, Nashville, Tennessee
b Department of Cardiac Surgery, Vanderbilt Children’s Hospital, Vanderbilt University Medical Center, Nashville, Tennessee
c Division of Cardiology, Baylor School of Medicine, Texas Children’s Hospital, Houston, Texas
d Division of Pediatric Cardiology, Department of Pediatrics, Kaiser Permanente, Honolulu, Hawaii
Accepted for publication June 28, 2007.
* Address correspondence to Dr Bichell, Division of Cardiac Surgery, Vanderbilt Children’s Hospital, Vanderbilt University Medical Center, 5247 Doctor’s Office Tower, 2200 Children’s Way, Nashville, TN 37232-9292 (Email: david.bichell{at}vanderbilt.edu).
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Abstract
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Left pulmonary artery hypoplasia in the setting of Fontan circulation predisposes to pulmonary artery discontinuity. We describe a novel approach to correct post-Fontan left pulmonary artery discontinuity by a strategy to produce isolated left pulmonary artery growth, followed by a catheter-based reincorporation of the left pulmonary artery into the Fontan circuit.
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Introduction
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Asymmetric pulmonary artery development and left pulmonary artery (LPA) hypoplasia may occur in patients with palliated single-ventricle physiology, resulting from hypoperfusion of the retro-aortic central pulmonary artery and hyperperfusion of the preferentially shunted rightward pulmonary artery. Unilateral pulmonary artery hypoplasia may worsen as passive pulmonary blood flow is instituted at conversion to cavopulmonary anastomosis. In extreme cases, the LPA may thrombose or become functionally atretic [1, 2]. Efforts to reincorporate an atretic or severely hypoplastic LPA into the Fontan circuit often meet with poor long-term success, as the condition of preponderant rightward flow persists when the caliber of the leftward artery is small, and discontinuity may recur.
It has been demonstrated in animal models that arteries subjected to chronic high-flow or low-flow states will remodel to increase or decrease their diameters accordingly, thereby preserving a constant shear stress [3, 4]. The molecular changes that take place in flow responsive remodeling are also being studied [5]. In clinical application of this principle, it is accepted that small pulmonary arteries grow in response to augmented blood flow either through an aortopulmonary shunt or a ventriculo-pulmonary conduit. We have applied the principles of flow responsive pulmonary artery remodeling to selectively cultivate the growth of a functionally atretic left pulmonary artery in isolation. We then successfully reincorporated the vessel into the Fontan circuit by a catheter-based approach. Long-term patency of the rehabilitated vessel has been demonstrated in follow up.
Our patient is now a 41/2-year-old girl with pulmonary atresia, intact ventricular septum, and right ventricular hypoplasia. She underwent balloon atrial septostomy and placement of a right-sided modified Blalock-Taussig shunt in the newborn period, a bidirectional cavopulmonary shunt at 21/2 months old, and she proceeded to a lateral baffle fenestrated Fontan procedure at 18 months of age. Bilateral chylothorax at 2 years of age prompted cardiac catheterization, which revealed an interval development of isolation of the left-sided pulmonary artery and hypoplasia of the left-sided pulmonary vascular bed. The LPA had measured 5.4 mm at 3 months prior to this finding, but catheterization showed the LPA was atretic, could only be opacified by retrograde left pulmonary vein injection, and was shown to be diminutive (Fig 1). The mean baffle and right pulmonary artery pressure was 14 mm Hg, the fenestration was patent, and the descending aortic saturation was 84%. Measurement of the LPA image in its under filled state is imprecise, but the best LPA diameter in a filled state was 3.8 mm, which was obtained by echocardiogram 2 weeks after the procedure (described as follows).
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Fig 1. (A) Comparison of post-Fontan anatomy demonstrating a fully patent right pulmonary artery and left pulmonary artery that is completely occluded proximally. (R = right pulmonary artery.) (B) The hypoplastic left pulmonary artery is visualized by a retrograde proximal descending aortogram revealing collaterals to both the right and left pulmonary arteries. (L = left pulmonary artery.)
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A staged cultivation of the hypoplastic left pulmonary artery was carried out using collaborative surgical and interventional techniques. A 4-mm left-sided aortopulmonary shunt was constructed to deliver high flow to the LPA in isolation, with the concurrent construction of a pericardial membranous separation of the left pulmonary artery from the Fontan baffle. A radio-opaque wire marker ring was placed at the site of the membranous partition constructed (Fig 2). Serial echocardiograms compared the LPA caliber with that of the right pulmonary artery. During the course of 10 months, the selectively shunt-perfused LPA grew to match the caliber of the right pulmonary artery and became suitable for reincorporation into the Fontan circuit. At 31 months of age, by catheterization, she underwent a radiofrequency perforation of the separating membrane, a balloon dilation, and implantation of a Palmaz Genesis 1910B stent (Johnson & Johnson Gateway, Piscataway, NJ) in the left pulmonary artery to reincorporate the rehabilitated vessel into the Fontan circuit. The modified Blalock-Taussig shunt was then coil occluded. At the time of stent implantation, the distal LPA measured 7.7 mm, the mean baffle pressure was 13 mm Hg, and the mean LPA pressure was 12 mm Hg (Fig 3).
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Fig 2. (A) Drawing represents a modified Blalock-Taussig shunt to a patch plasty of the diminutive left pulmonary artery (LPA) also showing the membranous separation between the Fontan baffle and the LPA. (B) Angiogram showing the isolated LPA 10 months after modification with modified Blalock-Taussig shunt (mBT) and the radio-opaque marker ring (M) of the membranous separation.
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Fig 3. Angiogram showing the rehabilitated left pulmonary artery reincorporated into the Fontan circuit after radiofrequency perforation of the membranous separation, balloon dilation, and stent (S) implantation. The modified Blalock-Taussig shunt (mBT) is coil occluded.
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At follow-up, 41 months postoperatively, she is active and asymptomatic. Her room air peripheral arterial oxygen saturations remain 85% to 95%. A computed tomographic angiogram shows that the LPA distal to the shunt is 9.2 mm, whereas the right pulmonary artery measured 9.8 mm, thus confirming that they are comparable in size. The fenestration is patent with an 8-mm gradient by echocardiogram.
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Comment
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An important stimulus of pulmonary artery growth is blood flow and resultant shear stress on the vascular endothelium [6–8]. Shear stress at the vascular endothelium causes coordinated upregulation of arterial endothelial nitric oxide synthase that may participate in the process of pulmonary vessel growth [5].
Applying principles of flow responsive pulmonary artery growth, a successful staged rehabilitation of LPA hypoplasia was achieved by first isolating the hypoplastic left pulmonary artery from the Fontan circuit and delivering obligate ipsilateral pulmonary blood flow through an aortopulmonary shunt. After satisfactory growth of the left-sided pulmonary arterial bed was achieved, the rehabilitated LPA was reincorporated into the Fontan circuit. The maximum diameter to which the stent can be dilated is 18 mm, which is predicted to accommodate growth to adulthood with periodic re-dilation. For patients with unilateral hypoplasia of the pulmonary arterial bed, an aortopulmonary shunt committed to the underdeveloped artery can encourage remedial growth. We have demonstrated a novel hybrid approach for successful rehabilitation of LPA hypoplasia.
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References
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Abstract
Introduction
