Ann Thorac Surg 2006;81:e18-e20
© 2006 The Society of Thoracic Surgeons
Case report
Aortopulmonary Fistula Occurring 4 Years After Replacement of the Ascending Aorta
Micha T. Maeder, MD
a
,
*
,
Thomas Wolber, MD
a
,
Andreas Künzli, MD
b
,
Michele Genoni, MD
b
,
Robert Blank, MD
a
,
Hans Rickli, MD
a
a Division of Cardiology, Department of Internal Medicine, Kantonsspital St. Gallen, Switzerland
b Division of Cardiothoracic Surgery, University Hospital of Zürich, Switzerland
Accepted for publication January 5, 2006.
* Address correspondence to Dr Maeder, Division of Cardiology, University Hospital Basel, Petersgraben 4, Basel, CH-4031 Switzerland (Email: micha.maeder{at}bluewin.ch).
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Abstract
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A 62-year-old man presenting with congestive heart failure due to a fistula between an aortic pseudoaneurysm and the right pulmonary artery is described. The shunt occurred 4 years after aortic valve and supracoronary graft replacement and was diagnosed by transesophageal contrast echocardiography. After redo surgery the patient made an uneventful recovery.
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Introduction
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Pseudoaneurysm of the ascending aorta is a rare complication after replacement of the ascending aorta [1]. We herein present the exceptional case of a fistula between an aortic pseudoaneurysm and the right pulmonary artery occurring several years after supracoronary graft replacement for type A aortic dissection.
A 62-year-old man was admitted with a new onset of congestive heart failure. His medical history was remarkable for aortic valve replacement with a Carbomedics 25 mm prosthesis for severe aortic stenosis and implantation of a dual chamber pacemaker for postoperative transient third-degree atrioventricular block 4 years ago. Three months after the initial operation, dilation of the ascending aorta (7.2 cm) with chronic type A aortic dissection had been diagnosed, and the patient had undergone reconstruction of the sinus portion (using gelatin resorcine formol glue) and supracoronary graft replacement using the inclusion technique with construction of a Cabrol shunt (ie, a shunt connecting the perigraft space and the right atrium [2]).
On admission, auscultation revealed rales over the basal lung fields, a metallic second heart sound, and a 4/6 systolic murmur at the right sternal border. The remainder of the physical examination was within normal limits. The patient did not have fever. His C-reactive protein and leukocyte count were within normal ranges, and blood cultures remained sterile. Transthoracic echocardiography revealed a hypertrophied left ventricle with normal systolic function, diastolic dysfunction, and an elevated mean pressure gradient across the aortic valve prosthesis of 22 mm Hg. There was mild tricuspid regurgitation with evidence of elevated systolic right ventricular pressure (transtricuspid gradient, 38 mm Hg; estimated right atrial pressure, 15 mm Hg). Fluoroscopy demonstrated normal opening and closing of the leaflets of the aortic valve prosthesis. Computed tomography showed a huge aortic pseudoaneurysm (maximal diameter, 10 cm) compressing the right pulmonary artery (Fig 1). Transesophageal echocardiography revealed a communication between the ascending aorta and the pseudoaneurysm at the level of the proximal anastomosis with systolic-diastolic flow from the aorta into the pseudoaneurysm (Fig 2). After injection of agitated 5% hydroxy-ethyl-starch into an antecubital vein, a significant amount of microbubbles appeared not only in the right-sided heart chambers but also in the pseudoaneurysm within a few seconds.
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Fig 1. Computed tomographic scan revealing a large pseudoaneurysm (P) surrounding the supracoronary graft (G) of the ascending aorta and compressing the right pulmonary artery (RPA). (D = descending aorta; LPA = left pulmonary artery.)
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Fig 2. (A) Transesophageal echocardiography showing flow (arrow) from the graft (G) into the pseudoaneurysm (P), and (B) appearance of microbubbles (asterisk) in the pseudoaneurysm (P), but not the graft (G) after injection of agitated hydroxy-ethyl-starch into a peripheral vein.
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At surgery, the Cabrol shunt was found to be obliterated. However, an 8-mm defect of the right pulmonary artery immediately after the bifurcation was found, and by this the previously inserted pulmonary artery catheter had entered the adjacent aortic pseudoaneurysm (Fig 3). The presence of a suture dehiscence between the graft and the native sinutubular junction was confirmed. The graft was replaced by a new prosthesis (Vascutek Gelweave, 28 mm), and subsequently patch repair of the right pulmonary artery with xenopericardium was performed. The postoperative course was uneventful. A transthoracic echocardiogram obtained 3 weeks later revealed that the mean pressure gradient across the aortic valve had decreased to 5 mm Hg.
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Fig 3. (A) Intraoperative view revealing a large defect in the right pulmonary artery (RPA), (B) which was closed with xenopericardium. (PT = pulmonary trunk; PC = pulmonary artery catheter.)
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Comment
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Pseudoaneurysm of the ascending aorta complicated by aortopulmonary fistula is an extremely rare type of left-to-right shunt [1, 3, 4] involving two defects at different anatomical locations. With regard to the mechanisms underlying the occurrence of pseudoaneurysm, re-dissection of the sinus portion associated with the previous use of gelatin resorcine formol glue has to be considered [5]. It has been speculated that the formalin component could have a necrotic effect on tissues, and thus might have facilitated re-dissection and dehiscence, respectively [1, 4]. In addition, the use of the inclusion technique might play a role. This method is often used in a situation where excessive bleeding is expected (eg, in case of redo surgery), but has been shown to be associated with the risk of pseudoaneurysm formation [6]. To overcome this problem, the consequent use of a Cabrol shunt to decompress the perigraft space has been recommended [6]; however, this was not successful in the present case, probably due to very early thrombotic occlusion of the shunt. The fistula itself may have developed after long-standing compression of the right pulmonary artery by the huge aortic pseudoaneurysm finally resulting in rupture. Other possible underlying conditions include infectious [7] and noninfectious inflammatory diseases [8]. However, endocarditis is not a very probable scenario regarding the fact that fever, embolism, and laboratory signs of systemic inflammation were absent, blood cultures were negative, and there was no macroscopic evidence of infection. Nevertheless, another inflammatory process such as giant cell aortitis [8] can not be completely excluded.
It may be unnecessary to point out that pulmonary catheter insertion did not cause the fistula, because a massively elevated mean pressure gradient across the aortic valve prosthesis (normal values for a Carbomedics 25-mm prosthesis in the aortic position: 9 ± 5 mm Hg) and appearance of microbubbles in the pseudoaneurysm after injection into a peripheral vein had indicated a high cardiac output and a shunt, respectively, already before surgery. In other cases, diagnoses of aortopulmonary fistula have been obtained by angiography. Alternatively, right heart catheterization can be used demonstrating an oxygen saturation step-up after blood from the aorta has entered the pulmonary circulation. In the present case, transesophageal echocardiography was a crucial examination as it could exclude serious complications of prosthetic valves (ie, valve obstruction and paravalvular leakage), obtained the diagnosis of a shunt and prompted surgery to be done. However, similarly to previous reports, echocardiography failed to directly visualize the fistula, and surgical exploration revealed the exact underlying anatomy. In conclusion, aortopulmonary fistula should be considered in a patient with an aortic pseudoaneurysm presenting with heart failure, and transesophageal contrast echocardiography may be helpful in establishing the diagnosis.
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References
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Abstract
Introduction
