Ann Thorac Surg 2005;80:1924-1928
© 2005 The Society of Thoracic Surgeons
Case report
Proximal Conduit Obstruction After Sano Modified Norwood Procedure
John J. Nigro, MD
a
,
*
,
Robert D. Bart, MD
b
,
Christopher D. Derby, MD
a
,
Mark S. Sklansky, MD
c
,
Vaughn A. Starnes, MD
a
a Department of Cardiothoracic Surgery, Los Angeles, California, USA
b Department of Anesthesiology, Critical Care Medicine, Los Angeles, California, USA
c Division of Cardiology; Department of Pediatrics, Childrens Hospital Los Angeles, Keck School of Medicine of the University of Southern California, Los Angeles, California, USA
Accepted for publication June 11, 2004.
* Address correspondence to Dr Nigro, Department of Cardiothoracic Surgery, Keck School of Medicine of the University of Southern California, Childrens Hospital Los Angeles, 4650 Sunset Blvd, Mailstop 66, Los Angeles, CA90027 (Email: jnigro{at}usc.edu).
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Abstract
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Sano and colleagues [1] recently described a modification of first stage palliation for hypoplastic left heart syndrome utilizing a right ventricle to pulmonary artery conduit. Preliminary results are favorable, but experience with this technique is limited. We report a case of sudden death due to obstruction of the proximal conduit by fibrointimal hyperplasia. This case of lethal conduit obstruction presented 3 months after initial palliation. Early cardiac catheterization and second stage palliation may be necessary to minimize the risk of such adverse events after the Sano modification.
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Introduction
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Recent reports suggest that the right ventricle to pulmonary artery conduit results in improved outcome of first stage palliation for hypoplastic left heart syndrome [1–3]. We describe a case of sudden death associated with proximal right ventricle to pulmonary artery conduit obstruction by fibrointimal hyperplasia.
Fetal echocardiography demonstrated hypoplastic left heart syndrome. The child was born at 38 weeks gestation and weighed 2.8 kg. After initiation of prostaglandin-E1 infusion the newborn was transferred to our center. Echocardiogram showed near mitral atresia, hypoplastic left ventricle, hypoplastic ascending aorta and transverse arch, coarctation, patent ductus arteriosus, good right ventricular function, and mild tricuspid regurgitation. On day 2 of life, a modified Norwood procedure was performed using a 5.0-mm polytetrafluoroethylene (Gore-tex, W.L. Gore & Assoc, Flagstaff AZ) conduit connecting the right ventricle to pulmonary confluence as described by Sano and colleagues [1]. Aspirin (40 mL daily) was initiated the day after surgery. The hospital course was uneventful, and the child discharged home on postoperative day 18 with room air saturations of 84% to 92%. A discharge echocardiogram revealed good right ventricular function, mild tricuspid regurgitation, and a peak velocity of 2.5 m/sec in the proximal right ventricle to pulmonary artery conduit. On routine follow-up at 3.5 months of age, the infant was noted to be cyanotic with room air saturation of 75%. However, the child was feeding well, gaining weight (4.9 kg), and had no respiratory symptoms. Echocardiogram revealed mild right ventricular dilatation with good systolic function and proximal right ventricle to pulmonary artery conduit narrowing with a peak velocity of 3.7 m/sec. A cardiac catheterization was subsequently scheduled, but the child suffered sudden death before catheterization.
The only significant finding on postmortem examination was proximal conduit obstruction by tissue extending from the endomyocardium (Fig 1). This tissue appeared to emanate directly from the endomyocardium and was easily peeled from the conduit (Fig 2). Histology revealed the presence of fibroblasts, myofibroblasts, and endothelial cells consistent with fibrointimal hyperplasia.
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Fig 1.
Black arrow (top image) marks the endomyocardial orifice of the proximal right ventricle to pulmonary artery conduit viewed from "inside" the right ventricular chamber. In the bottom image the ventricular wall surrounding the proximal conduit origin (black arrow) has been removed from the heart and photographed from its endocardial surface. The "whitish" tissue surrounding the orifice emanated from endomyocardium and obstructed the proximal conduit. This tissue was found to be fibrointimal hyperplasia on histology.
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Fig 2. Longitudinal section of the proximal right ventricle to pulmonary artery conduit through the ventricular origin. The black arrow marks the conduit. The fibrointimal hyperplasia that obstructed the proximal conduit is outlined (black dots).
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Comment
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Hypoplastic left heart syndrome is fatal without surgical palliation or cardiac transplantation [4–8]. Palliation is initiated in the neonatal period with the Norwood procedure, utilizing a modified Blalock-Taussig shunt to provide pulmonary blood flow (Fig 3) [4–8]. The combination of a single right ventricle and the modified Blalock-Taussig shunt provides significant management challenges in the period immediately after first stage palliation, resulting in reported mortality of up to 50% [4–8]. To improve results, Sano and colleagues [1] proposed a modification of the Norwood procedure in which a right ventricle to pulmonary artery conduit is constructed to provide pulmonary blood flow in place of the modified Blalock-Taussig shunt (Fig 3). According to proponents and recent reports, this modification provides a higher diastolic blood pressure, improved coronary artery perfusion, and improved perioperative outcomes [1–3]. Unlike the modified Blalock-Taussig shunt, which has been performed for many years, little data are available on the long-term consequences of the Sano modified Norwood procedure. The pathophysiology and appropriate medical management for neonates after this procedure are not well documented. As demonstrated in this report, a sudden conduit- related death can occur after the Sano modified Norwood procedure. Although Sano and colleagues [1] alluded to progressive conduit obstruction and subsequent patient demise, this process has not been well characterized. Discrete stenosis of the proximal conduit (Fig 4) and dynamic narrowing in the myocardium (Fig 5) below the conduit origin have been evident on pre-Glenn cardiac catheterization in other patients at our center with episodic cyanosis after the Sano modified Norwood procedure. We believe the dynamic myocardial narrowing is due to ventricular hypertrophy and can cause cyanotic spells similar to those occurring in Tetrology of Fallot ("hypercyanotic episodes"). In both settings, variations in systemic vascular resistance, contractility, and pulmonary vascular resistance can dramatically affect pulmonary blood flow and (the resulting) arterial saturations. Therefore, low systemic pressure and hypercontractile states can potentiate the obstruction to pulmonary blood flow in these patients.
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Fig 3. (A) First stage palliation with modified Blalock-Taussig shunt for pulmonary connection. (B) First stage palliation with right ventricle to pulmonary artery conduit as described by Sano and colleagues [1].
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Fig 4. Stenosis of the proximal right ventricle to pulmonary artery conduit (white arrows) in an angiogram obtained from another patient who underwent evaluation for cyanosis after the Sano modified Norwood procedure. The asterisk (*) marks the mid-portion of the right ventricle to pulmonary artery conduit and the V marks the ventricular chamber.
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Fig 5. These images were obtained from another patient who had hypercyanotic spells after the Sano modified Norwood procedure. The conduit is marked with an asterisk (
*
) and the ventricular chamber is outlined with white dots in both images (top and bottom) (ventriculograms). The concavity present in the top image (systole) represents dynamic obstruction within the ventricular myocardium below the origin of the right ventricle to pulmonary artery conduit (restricting pulmonary blood flow).
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Episodic cyanosis after the Sano modified Norwood procedure may be a sentinel of sudden death due to conduit obstruction. Medical interventions (including increasing systemic afterload, reducing contractility, and volume resuscitation) may stabilize these patients acutely. However, an early Glenn shunt or placement of a systemic to pulmonary artery shunt may be necessary. Because the lethal conduit obstruction reported here presented 3 months after first stage palliation, early cardiac catheterization and second stage palliation may be necessary to minimize the risk of this adverse outcome after the Sano modified Norwood procedure.
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References
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- Sano S, Ishino K, Kawada M, et al. Right ventricle-pulmonary artery shunt in first-stage palliation of hypoplastic left heart syndrome J Thorac Cardiovasc Surg 2003;126(2):504-509.[Abstract/Free Full Text]
- Pizarro C, Malec E, Maher KO, et al. Right ventricle to pulmonary artery conduit improves outcome after stage I Norwood for hypoplastic left heart syndrome Circulation 2003;108(Suppl 1):I155-I160.
- Pizarro C, Norwood WI. Right ventricle to pulmonary artery conduit has a favorable impact on postoperative physiology after Stage I Norwoodpreliminary results. Eur J Cardio-Thorac Surg 2003;23(6):991-995.[Abstract/Free Full Text]
- Helton JG, Aglira BA, Chin AJ, Murphy JD, Pigott JD, Norwood WI. Analysis of potential anatomic or physiologic determinants of outcome of palliative surgery for hypoplastic left heart syndrome Circulation 1986;74(3 Pt 2):170-176.
- Murdison KA, Baffa JM, Farrell Jr PE, et al. Hypoplastic left heart syndrome. Outcome after initial reconstruction and before modified Fontan procedure Circulation 1990;82(Suppl 5):199-207.
- Norwood WI, Kirklin JK, Sanders SP. Hypoplastic left heart syndromeexperience with palliative surgery. Am J Cardiol 1980;45(1):87-91.[Medline]
- Norwood WI, Lang P, Casteneda AR, Campbell DN. Experience with operations for hypoplastic left heart syndrome J Thorac Cardiovasc Surg 1981;82(4):511-519.[Abstract]
- Pigott JD, Murphy JD, Barber G, Norwood WI. Palliative reconstructive surgery for hypoplastic left heart syndrome Ann Thorac Surg 1988;45(2):122-128.[Abstract]
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Abstract
Introduction
