CT Appearance of Thoracic Aortic Graft Complications

Transcription

1 CT of ortic Graft Complications Cardiopulmonary Imaging Clinical Observations Baskaran Sundaram 1 Leslie Eisenbud Quint 1 Smita Patel 1 Himanshu J. Patel 2 G. Michael Deeb 2 Sundaram B, Quint LE, Patel S, Patel HJ, Deeb GM Keywords: aorta, cardiovascular imaging, CT, CT angiography, postoperative complications, thoracic DOI: /JR Received September 21, 2005; accepted after revision January 24, Department of Radiology, University of Michigan Health System, 1500 E Medical Center Dr., Box 0302, nn rbor, MI ddress correspondence to B. Sundaram (sundbask@umich.edu). 2 Division of Cardiothoracic Surgery, Department of Surgery, University of Michigan Health System, nn rbor, MI. JR 2007; 188: X/07/ merican Roentgen Ray Society CT ppearance of Thoracic ortic Graft Complications OBJECTIVE. The purpose of this study was to document the spectrum of CT findings and the clinical outcome of thoracic aortic graft complications. CONCLUSION. ortic graft complications detected with CT may or may not be clinically apparent and/or relevant. CT characterization in combination with clinical findings helps to determine patient treatment. ortic interposition grafting is widely accepted in the management of thoracic aortic aneurysm and dissection. Reported complications include anastomotic dehiscence and graft infection [1, 2]. Follow-up CT scans are generally obtained on a routine basis to evaluate for potential complications that may or may not be clinically evident. t our institution, these routine scans are obtained approximately 3 and 12 months after surgery and annually after that. The aim of our study was to document the spectrum of CT findings and the clinical outcome among patients with thoracic aortic graft complications detected with CT. Materials and Methods Institutional review board approval was obtained for this study. Patients were retrospectively identified through a search of the institutional radiology database for chest CT reports generated between 1998 and 2004 that suggested the presence of a postoperative aortic graft complication on the basis of imaging findings. The keywords used for the computerized search were graft or surgery plus leak or extravasation or dehiscence or outpouching or rupture. The imaging studies were retrieved and reviewed on a workstation by two experienced chest radiologists, and a consensus interpretation was generated. Patients were included in the study if review of the CT examinations showed any of the following findings: extravasation of contrast material, an unusually large amount or increasing amount of low-attenuation material adjacent to the graft, perigraft gas bubbles, and graft herniation into the chest wall. Patients were excluded if CT showed a small amount of perigraft low-attenuation material (< 10 mm thick) consistent with normal postoperative hematoma. CT scans were performed with an IV bolus of contrast material and thin (1.25- to 3-mm collimation) overlapped sections on a variety of helical scanners. Most CT examinations were performed for routine postsurgical followup, although a few were performed for evaluation of a clinically suspected complication. xial images from the CT examinations were analyzed for the location of perigraft low-attenuation collections and contrast collections and for change in size of these collections if several examinations had been performed on an individual patient. Scans also were evaluated for the abnormal presence of gas adjacent to the graft, for evidence of fistula formation with adjacent structures, and for abnormal graft position (e.g., chest wall herniation). Clinical patient records were reviewed to obtain information regarding type of surgery performed (Figs. 1 3), time interval between surgery and imaging, and treatment and outcome after the CT examination. Results Thirty-nine episodes of graft complications (Table 1) were identified in 34 patients. Five patients had more than one separate episode of complication. bnormal Perigraft Low-ttenuation Material Twenty of 39 complications consisted of abnormal distribution of low-attenuation material around the aortic graft (Figs. 4 and 5). The abnormal low-attenuation material was adjacent to a graft in the aortic root in five patients, ascending aorta in five patients, aortic arch in two patients, and descending aorta in eight patients. These collections were detected 1 week 30 months after surgery. In one of these patients, the descending aortic graft also had herniated into the posterolateral chest wall. JR:188, May

2 Only one of 20 patients was receiving anticoagulation therapy. Eight of 20 patients had proven (three patients) or presumed (five patients) graft infections. Two of these patients had gas bubbles in the mediastinum. Four patients with infection underwent surgical exploration with drainage of a mediastinal abscess. ll four of the patients with infections who did not undergo surgery were treated with antibiotics. Follow-up CT of three of these patients showed a decrease in the amount of abnormal low-attenuation material. The fourth patient did not undergo follow-up imaging. Twelve of 20 patients had no clinical evidence of graft infection. One patient underwent surgical exploration that revealed a large hematoma, probably caused by anastomotic dehiscence. nother patient experienced acute hypotension and died, presumably of anastomotic dehiscence and exsanguination. The other 10 patients had no symptoms and were not treated for the imaging finding initially detected 4 13 months after surgery. Follow-up CT examinations of four of these patients 3 32 months later showed partial resolution (two patients), stability (one patient), and progression then regression (one patient) of the finding. During the surgical procedures on seven of the 10 patients, fibrin glue had been applied at the graft anastomoses, and B Fig. 1 Total aortic root technique (modified Bentall)., Drawing shows complete resection of native aortic root. Prosthetic valved conduit is sutured to aortic valve annulus in proximal aspect. Native coronary arteries are reimplanted as buttons (arrows) in prosthesis. B, Drawing shows distal anastomosis (arrowheads) to ascending aorta. rrow indicates reimplanted coronary artery. Fig. 2 Inclusion root technique., Drawing shows bioprosthetic valved conduit within native aortic root. Graft is anchored in proximal aspect with series of interrupted sutures to horizontal plane at nadir of aortic annulus (curved arrows). Buttons are resected from valved conduit for subsequent native coronary artery reimplantation (straight arrows). sterisks indicate space where small perigraft contrast pools occur in some patients. Dashed line indicates aortic valve plane. B, Drawing shows running suture line attaching distal aspect of valved conduit to aorta. Straight arrow indicates site of coronary artery reimplantation; curved arrows, proximal graft anastomosis. C, Drawing shows completed repair. Unlike total aortic root technique in Figure 1, inclusion root technique results in placement of valved conduit within native aortic root. Straight arrow indicates site of coronary artery reimplantation; curved arrows, proximal graft anastomosis. seven of the 10 patients had bovine pericardium covering a graft. Pockets of Contrast Material Outside Inclusion Root Grafts Six of 39 imaging complications consisted of small collections of contrast material outside the aortic lumen, between the porcine inclusion root graft and the surrounding native aortic wrap without extension into the mediastinum (Fig. 6). Three of six collections appeared to arise from dehiscence at the right coronary artery button. In the other three patients, the origin of the collection could not be determined. These collections were detected 1 78 months 1274 JR:188, May 2007

3 CT of ortic Graft Complications Fig. 3 Drawing shows total aortic arch replacement with separate individual great vessel anastomoses. Thick straight arrows indicate proximal and distal aortic anastomoses. nastomoses between graft side branches and native arch vessels (thin straight arrows), graft cannulation site (arrowhead), and sewn site of unused graft side branch site (curved arrow) also are shown. after surgery, and all were asymptomatic. ll patients underwent echocardiography, and none of the collections was detected with that technique. In three of the six patients, follow-up CT examinations 8 51 months later showed stable findings. Two additional patients did not undergo imaging follow-up. Three of these five patients were taking aspirin, and none was treated for this imaging finding. The sixth patient was taking aspirin. fter detection of the abnormal contrast collection on imaging, aspirin was suspended, and the imaging finding was not present on CT 4 months later. spirin therapy was resumed, and follow-up CT 6 months later showed no recurrence of abnormal contrast collection. TBLE 1: ortic Graft Complications Evident on CT (n =34) CT Finding No. Pockets of contrast material outside 6 inclusion root grafts Mediastinal contrast extravasation 13 bnormal perigraft low-attenuation material 20 Mediastinal gas 4 ortoesophageal fistula 1 ortopulmonary fistula 1 Graft herniation into thoracotomy defect 1 Note Five patients had more than one complication. Mediastinal Contrast Extravasation Thirteen of 39 complications consisted of mediastinal collections of extravasated contrast material outside the aorta (Figs. 7 and 8). graft or patch was present in the aortic root in six patients, in the ascending aorta in four patients, in both root and ascending aorta in one patient, in the arch only in one patient, and in both ascending aorta and arch in one patient. Extravasation appeared to arise from a proximal or distal graft anastomosis in nine cases, from a coronary artery button anastomosis in three cases, and from a graft cannulation site in one case. These collections were detected 1 month 18 years after surgery. Two of 13 patients had gas bubbles in the mediastinum. One case of bubbles was due to an aortoesophageal fistula (Fig. 8), and the other was likely due to infection. One patient without mediastinal gas also had an aortopulmonary fistula. In seven of 13 patients with contrast extravasation, the cause appeared to be graft infection (four proven cases and three presumed). Eight of 13 patients were undergoing anticoagulation therapy, and one of 13 was taking aspirin. Six of 13 patients underwent follow-up CT examinations 7 20 months after the initial CT. In two patients, the collection of contrast material resolved, one after antibiotic therapy alone, and the other after antibiotic therapy and deployment of embolization coils within the pseudoaneurysm. In the third patient, the contrast collection first decreased and then remained stable after discontinuation of anticoagulation therapy. In the fourth patient, the extravasation waxed and waned on several subsequent examinations after antibiotic treatment and discontinuation of anticoagulation. Operative exploration eventually revealed infection and leak at the graft cannulation site. In the fifth patient, who had no symptoms, the small collection of extravasated contrast material increased minimally, and no treatment was administered. The sixth patient was treated with antibiotics, and the leak was stable on follow-up CT examinations. Seven of 13 patients did not undergo follow-up CT examinations. Two of these patients had proven and two had presumed graft infections causing the leak, and three had no clinical evidence of infection. Of the four patients with infection, three underwent surgical repair, and one died of exsanguination. Of the three patients without infection, one underwent surgical repair, one deferred treatment, and one transferred to another hospital. Fig year-old man 1 month after descending thoracic aortic graft replacement for posttraumatic contained aortic rupture., Routine CT scan shows minimal perigraft low-attenuation material (arrows). rrowhead indicates felt pledget at graft cannulation site. B and C, xial (B) and sagittal reformatted (C) CT scans 12 months after show marked increase in amount of perigraft low-attenuation material (arrows). Patient, who had no symptoms and no clinical evidence of infection, was not treated for this imaging finding. rrowhead indicates felt pledget at graft cannulation site. JR:188, May

4 Fig year-old woman 15 months after ascending aortic graft replacement for aortic aneurysm. CT scan obtained because patient felt chest wall heaviness reveals abnormal perigraft low-attenuation material (arrows). Surgical drainage revealed purulent fluid. Discussion pproximately 250 thoracic aortic graft replacement operations are performed each year at our institution. Only 39 CT-evident complications were identified over a 7-year period, suggesting a very low complication rate. The most frequent type of complication was abnormal accumulation of low-attenuation material around the graft, and the next most frequent was collections of contrast material outside the graft. ccumulation of low-attenuation material around the graft often was due to infection, although bleeding due to anastomotic dehiscence without infection appeared to be a less frequent cause. In one half of patients with accumulation of low-attenuation material, the cause was not identified, and the patients continued to have no symptoms. We hypothesize that these perigraft low-attenuation collections might have been the result of postoperative seroma and/or inflammatory edema developing as a result of an allergic reaction to the aortic graft material or the surrounding bovine pericardium [3, 4]. Yamamoto et al. [3] noted that collagen-impregnated vascular grafts may have contaminants containing endotoxin and (1 3)b-D-glucan and causing a sterile inflammatory response around the graft. patient at our institution (not included in this study) who did not have symptoms underwent CT-guided aspiration of such a perigraft fluid collection that had increased in size over several months. The aspirated fluid was sterile, clear, and yellow, and laboratory values were consistent with seroma. In a specific subset of patients with extravasation of contrast material outside the graft, the contrast collections appeared to be confined between the porcine aortic root graft and the surrounding native aortic wrap (i.e., inclusion root grafts). This imaging complication did not appear to have clinical significance because the patients continued to be free of symptoms. Subsequent imaging examinations showed that the collections had not increased and that in some patients they had resolved. Using echocardiography, Oechslin et al. [5] found that a perfused echo-free space (pseudoaneurysm) between an aortic root homograft and the native aortic wall was a common finding (22 of 30 patients). Willems et al. [6] reported similar echocardiographic findings in 15% (12/79) of patients who had undergone subcoronary implantation of an aortic valve homograft. Those authors, however, did not see this finding in patients who had received aortic root homografts. Oechslin et al. suggested that the leaks were due to partial dehiscence at the proximal suture line. We believe that these small contrast pools may be the result of tiny leaks at the coronary artery or proximal graft anastomoses. In our study, the leaking contrast material in three of six patients appeared to come from dehiscence in the region of the right coronary artery button. The origin of the leak in the other three patients was not obvious. Rofsky et al. [7] found leakage between an ascending aortic graft and the surrounding native aortic wrap on MRI in 15% (5/34) of patients and on CT in 17% (4/24). Those grafts were synthetic rather than tissue grafts, and three of the five patients with leaks had grafts limited to the supravalvular region of the aorta. Therefore, the findings are probably not comparable with those in our study. Whereas pseudoaneurysms contained within a surrounding native aortic wall in patients with inclusion root grafts appeared to be clinically insignificant, extravasation of contrast material outside the aorta into the mediastinum in patients with any type of graft was most often associated with anastomotic infection (eight of 13 patients). nticoagulation, however, appeared to be a factor in a minority of cases. Surgical or angiographic intervention was performed on most patients with this finding. Fig year-old man 1 month after porcine aortic root replacement for type 1 aortic dissection. C, Routine follow-up axial ( and B) and coronal reformatted (C) CT scans show small pockets of contrast material (arrows) in space between inclusion root graft and surrounding native aortic wrap, apparently arising from right coronary artery button anastomosis. ppearance did not change on CT scans obtained over 5-year period, and condition remained asymptomatic. rrowhead (B) indicates right coronary artery JR:188, May 2007

5 CT of ortic Graft Complications Fig year-old man taking anticoagulation therapy 27 months after aortic arch replacement for chronic type aortic dissection. C, xial ( and B) and sagittal reformatted (C) CT scans obtained because of clinical suspicion of mediastinal hematoma and infection show active contrast extravasation (white arrows) arising from cannulation site in graft and extending into sternotomy defect in anterior chest wall. Leak and infection at cannulation site were confirmed at subsequent surgical repair. Straight black arrows indicate distal graft anastomosis; arrowhead (), felt pledget at cannulation site; curved arrows ( and B), dissection flap in native aorta. In our study, CT findings suggestive of complications occurred at any time up to 18 years after surgery. previous study [8] also showed late occurrence of graft dehiscence. This finding suggests that imaging surveillance should be performed on a continuing basis for patients with aortic grafts. potential limitation of our study was the lack of standardization of imaging follow-up of these complications. The follow-up evaluations were individually dictated by each patient s complex and diverse clinical status and course. Our data suggest that thoracic aortic graft complications are uncommonly detected at CT. It is essential, however, to be aware of the spectrum of CT findings of these complications so that life-threatening conditions can be diagnosed when they do occur. pparent complications on CT are of little or no clinical significance, and knowledge of the surgical details and the patient s clinical status is important for accurate interpretation of imaging findings. References 1. Dossche KM, Tan ME, Schepens M, Morshuis WJ, de la Riviere B. Twenty-four year experience with reoperations after ascending aortic or aortic root replacement. Eur J Cardiothorac Surg 1999; 16: Coselli JS, Koksoy C, LeMaire S. Management of thoracic aortic graft infections. nn Thorac Surg 1999; 67: Yamamoto K, Noishiki Y, Mo M, Kondo J, Matsumoto. Unusual inflammatory responses around a collagen-impregnated vascular prosthesis. rtif Organs 1993; 17: Moore M, Phillips RE. Biocompatibility and immunologic properties of pericardial tissue stabilized by dye-mediated photo oxidation. J Heart Valve Dis B Fig year-old woman with unremitting sternotomy wound infection and mediastinitis 12 months after ascending aorta and aortic arch replacement for aortic aneurysm., CT scan shows small pockets of contrast extravasation (curved black arrow) at graft anastomosis (arrowhead) consistent with dehiscence. Finding was confirmed at surgery. B, CT scan shows tethering (curved arrow) of midthoracic esophagus and mediastinal gas (straight arrow), suggesting aortoesophageal fistula. Findings were confirmed at surgery. rrowheads indicate graft anastomosis 1997; 6: Oechslin E, Carrel T, Ritter M, et al. Pseudoaneurysm following aortic homograft: clinical implications? Br Heart J 1995; 74: Willems TP, Van Herwerden L, Taams M, Kleyburg-Linker VE, Roelandt JR, Bos E. ortic allograft implantation techniques: pathomorphology and regurgitant jet patterns by Doppler echocardiographic studies. nn Thorac Surg 1998; 66: Rofsky NM, Weinreb JC, Grossi E, et al. ortic aneurysm and dissection: normal MR imaging and CT findings after surgical repair with the continuous-suture graft-inclusion technique. Radiology 1993; 186: Henriques JP, Brutel de la Riviere, Schepens M, Ernst JM. Percutaneous occlusion of the entry to a leaking false aneurysm after ascending aortic replacement for aortic dissection type facilitating surgical repair. Eur J Cardiothorac Surg 1997; 11: JR:188, May