Ann Thorac Surg 2005;80:338-340
© 2005 The Society of Thoracic Surgeons
Case report
Nitric Oxide in Pulmonary Arteriovenous Malformations and Fontan Procedure
Gonzalo E. Urcelay, MDa,*,
Arturo J. Borzutzkya,
Pedro A. Becker, MDb,
Maria E. Castillo, MDc
a Department of Pediatrics, Pontificial Catholic University of Chile, Santiago, Chile
b Department of Cardiovascular Diseases, Pontificial Catholic University of Chile, Santiago, Chile
c Hospital Sótero del Río, Santiago, Chile
Accepted for publication December 29, 2003.
* Address reprint requests to Dr Urcelay, Pontificial Catholic University of Chile, Department of Pediatrics, Lira 85, Santiago 833-0074, Chile; (Email: gurcelay{at}manquehue.net).
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Abstract
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Pulmonary arteriovenous malformations are a well documented complication of superior cavopulmonary (Glenn) connections. We report the successful management of a case of severe hypoxemia in the early postoperative period of a patient who underwent the Fontan operation. The patient had previously been diagnosed with pulmonary arteriovenous malformations; the use of inhaled nitric oxide was followed up with reversal of life-threatening hypoxemia. At 6-month postoperative follow-up, the patient was asymptomatic with near normal aortic saturation.
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Introduction
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Connection between the superior vena cava and the pulmonary arteries (bidirectional Glenn anastomosis) may be complicated by the development of pulmonary arteriovenous malformations (PAVMs) with intrapulmonary right-to-left shunting and progressive cyanosis. Pulmonary arteriovenous malformations were first described after the classic Glenn shunt in the late 1950s, and as many as 20% of patients develop PAVMs after cavopulmonary anastomoses for single-ventricle physiology [1]. The pathogenesis of PAVMs is unclear, but it has been linked to either the absence of pulsatility in the pulmonary circulation or the absence of hepatic venous effluence in the lungs. Initially the diagnosis was based on pulmonary angiography. In recent years, contrast echocardiography has proved to be a sensitive tool for the detection of PAVMs. Different approaches have been attempted for treatment of PAVMs. If the PAVMs are isolated, surgery or selective embolization are good treatment alternatives; however in patients with cavopulmonary shunts, PAVMs are diffuse in nature [2]. Complete resolution of these malformations has been reported after the Fontan procedure [3, 4]. Here we describe the successful administration of inhaled nitric oxide in a patient with PAVMs who underwent the Fontan procedure with a postoperative period complicated by severe hypoxemia.
The patient is a 2-year-old girl born with heterotaxia syndrome with polysplenia, hypoplastic left ventricle with aortic and mitral stenosis, supra-mitral membrane, hypoplastic aorta, aortic coarctation, interrupted inferior vena cava with azygos continuation to superior vena cava, bilateral superior vena cava, and a ventricular septal defect. At 17 days of age she underwent a modified Norwood procedure. Subsequently, at the age of 7 months, a Kawashima procedure was performed with bilateral anastomosis of superior vena cava to both pulmonary arteries and takedown of the modified Blalock-Taussig shunt. She was scheduled for a Fontan procedure at 2 years of age because of progressive aortic de-saturation with profound cyanosis and recurrent respiratory infections.
On admission, the patient’s arterial oxygen saturation (SaO2) in room air was 70%, her blood pressure was 83/63 mm Hg, and her heart rate was 100 beats per minute. Her hematocrit was 68%. Preoperative catheterization revealed an unobstructed flow through both the aortopulmonary anastomosis and the superior cavopulmonary connection. Mean pulmonary artery pressure was 12 mm Hg with pulmonary oxygen saturation of 60%. Contrast echocardiography was performed by rapid administration of saline through a peripheral intravenous catheter in the right upper extremity. Microcavitations were seen in the left atrium within less than two cardiac cycles of injection, establishing the diagnosis of PAVMs. No extracardiac collateral vessels were seen that could explain the right-to-left shunting.
The Fontan operation was performed under moderate hypothermic bypass with no aortic cross clamp, using an extracardiac 20 mm politetrafluorethylene conduit between the inferior vena cava and right pulmonary artery. A fenestration was not performed because of persistently low SaO2 after completion of the extracardiac Fontan and the belief that PAVMs would act as a "fenestration." The patient came off bypass on dopamine and nitroglycerin; central venous pressure was 15 mm Hg, left atrial pressure was 7 mm Hg, and SaO2 was 72%. Intraoperative transesophageal contrast echocardiography confirmed previous finding of pulmonary arteriovenous fistulas. On postoperative day 1, weaning from mechanical ventilation was attempted but failed because of postextubation laringeal spasm with a fall of SaO2 to 60%. On postoperative day 2, the patient’s SaO2 levels were persistently low (<70%) with 100% of inspired oxygen. Due to life-threatening hypoxemia with SaO2 of 50% to 55%, we decided to administer inhaled nitric oxide (iNO) at 40 ppm. Within minutes a dramatic rise in SaO2 was observed. During the next few days SaO2 levels increased to 80% and to 85%, and the patient was finally extubated 8 days postoperatively. Inhaled nitric oxide was slowly weaned from 40 ppm to 5 ppm and was discontinued 12 hours after successful extubation. The patient was discharged home on postoperative day 12 with SaO2 levels between 77% and 85%, and she was prescribed digoxin, diuretics, and captopril. Six months postoperatively, she is doing very well and is asymptomatic with SaO2 levels of 90% to 92%.
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Comment
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Pulmonary arteriovenous malformations are abnormal communications between pulmonary arteries and veins. Pathologically, dilated capillary and precapillary vessels with evidence of direct arteriovenous communication are seen. They may be hereditary as in Rendu-Osler-Weber syndrome, or acquired as in hepatopulmonary syndrome, or in complex congenital heart defects with single ventricle physiology palliated by superior cavopulmonary connections. Various hypotheses try to explain the pathogenesis of PAVMs in these patients, one of which is the nonpulsatile nature of the systemic to pulmonary venous connections. However, patients intervened with the Fontan operation seldom have PAVMs develop. Even more, after reconnecting hepatic veins to the cavopulmonary circulation, a complete regression of PAVMs may be observed [4]. In recent years, wide belief has developed that a so-called "hepatic factor" is critical in preserving the integrity of pulmonary vasculature in normal subjects. The absence of this factor in pulmonary circulation as in classic Glenn operations would permit the development of PAVMs. This hepatic factor could be related to regulators of nitric oxide, the polypeptide super family transforming growth factor and its antagonists; the absence of the latter would produce an unopposed pulmonary vasodilatation leading to PAVMs [4, 5].
Few reports have documented the use of iNO in the postoperative period of Fontan operations in patients with PAVMs. In a very similar case to ours, Hofer and colleagues [6] reported successful administration of iNO for life-threatening hypoxemia after a nonfenestrated extracardiac Fontan procedure. Others have reported use of iNO in patients with PAVMs with other pathologies or heart surgeries. Bacha and colleagues [7] used iNO in a patient with heterotaxia syndrome and PAVMs who required a heart transplant with regression of hypoxemia. Gamillscheg and colleagues [8] administered iNO in the early postoperative period of 13 patients after Fontan and bidirectional Glenn procedures and observed a significant improvement of hemodynamic conditions. However, the presence of PAVMs is not mentioned in this study.
The physiologic explanation of improvement of SaO2 in patients with PAVMs after iNO administration has not been completely elucidated. Arteriovenous fistulas are low resistance pathways so that increased pulmonary resistance in the surrounding area lead to increased shunting. Consequently iNO may induce selective vasodilation of well-ventilated pulmonary areas leading to an improvement of ventilation-perfusion physiology, and by reducing pulmonary vascular resistance this would divert flow from the fistulas, thus reducing hypoxemia. This report adds evidence to be considered in the early postoperative treatment of Fontan patients with demonstrated PAVMs.
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References
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- Bernstein HS, Brook MM, Silverman NH, Bristow J. Development of pulmonary arteriovenous fistulae in children after cavopulmonary shunt Circulation 1995;92:II309-II314.
- Duncan BW, Kneebone JM, Chi EY, et al. A detailed histologic analysis of pulmonary arteriovenous malformations in children with cyanotic congenital heart disease J Thorac Cardiovasc Surg 1999;117:931-938.[Abstract/Free Full Text]
- Knight WB, Mee RB. A cure for pulmonary arteriovenous fistulas? Ann Thorac Surg 1995;59:999-1001.[Abstract/Free Full Text]
- Shah MJ, Rychik J, Fogel MA, Murphy JD, Jacobs ML. Pulmonary AV malformations after superior cavopulmonary connectionresolution after inclusion of hepatic veins in the pulmonary circulation. Ann Thorac Surg 1997;63:960-963.[Abstract/Free Full Text]
- Ashrafian H, Swan L. The mechanism of formation of pulmonary arteriovenous malformations associated with the classic Glenn shunt (superior cavopulmonary anastomosis) Heart 2002;88:639.[Free Full Text]
- Hofer A, Pusch M, Haizinger B, Mair R, Gitter R, Gombotz H. Successful management of severe life-threatening hypoxemia due to pulmonary arteriovenous malformation Anesthesiology 2002;97:1313-1315.[Medline]
- Bacha EA, Jonas RA, Mayer Jr JE, Perry S, del Nido PJ. Management of pulmonary arteriovenous malformations after surgery for complex congenital heart disease J Thorac Cardiovasc Surg 2000;119:175-176.[Free Full Text]
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Abstract
Introduction
