MR imaging of complications of aortic surgery

Sixteen patients with a variety of complications of aortic surgery were evaluated with magnetic resonance (MR) imaging. More than one complication occurred in seven patients, resulting in the following types of abnormalities: graft occlusions, two; graft infections; five; pseudoaneurysms or aneurysmal dilatation of graft anastomoses, 10; perigraft hemorrhages, four; and aortoenteric fistulas, two. The MR findings were verified by surgery in 10, by CT in four, and by angiography in 11 patients. The size and extent of pseudoaneurysm or anastomotic dilatation, the presence of thrombus and vessel occlusion, the extent of abscesses, and the effect of pseudoaneurysms and abscesses on adjacent structures were readily demonstrated by MR. The size of the residual lumen in the case of thrombosis could be assessed. Abscesses were identified by their characteristic signal increase with long repetition rates and long echo delays. Magnetic resonance was also able to exclude suspected complications such as perigraft infection, hemorrhage, and graft occlusion in four patients.     

Aortoenteric fistula and perigraft infection: evaluation with CT

A blinded retrospective study was performed to determine the sensitivity and specificity of computed tomography (CT) in detecting perigraft infection (PGI) and aortoenteric fistula (AEF), rare but devastating complications of aortic reconstructive surgery. Two observers independently reviewed CT scans in 55 cases including AEF (n = 23); PGI (n = 12); and normal, noninfected grafts (n = 20). Each scan was assessed for ectopic gas, focal bowel wall thickening, perigraft fluid, perigraft soft tissue, pseudoaneurysm formation, disruption of the aneurysmal wrap, and increased soft tissue between the graft and surrounding wrap. Comparison of CT findings with operative results revealed that each observer correctly identified as abnormal 33 of 35 cases of PGI either with or without AEF (sensitivity, 94%) and that results were falsely positive in three cases (specificity, 85%). CT findings ranged from large amounts of perigraft soft tissue and ectopic gas to subtle findings of minimal or no abnormalities; thus, strict criteria must be applied to the interpretation of CT scans after aortic surgery. Although CT is not 100% sensitive or specific, the authors conclude that it will continue to be valuable for diagnosing PGI and AEF.     

Ga-67 citrate scan in vascular graft infection

The clinical utility of the Ga-67 scan has been studied in 9 patients with clinical suspicion of vascular graft infection. Eleven grafts were analyzed: 4 aortobifemoral, 2 iliofemoral, 3 femoropopliteal, 1 axillofemoral, and 1 axillobifemoral. The Ga-67 scan was positive in 8 grafts with bacteriological proof of infection and negative in 3 grafts in which infection was ruled out by clinical follow-up. A Ga-67 scan also demonstrated the spread of infection to the thigh in two patients and to the pelvis in another two patients. In 4 patients CT was performed. The CT findings included graft thrombosis, perigraft fluid collection and thickened graft wall. No discrepancies were found between the CT scan and Ga-67 scan. In three patients a control Ga-67 scan was carried out after specific antibiotic and surgical treatment. Two of these showed increased Ga-67 uptake and spreading of infection along the graft; in the other patient, a Ga-67 scan revealed normalization after resolution of an abdominal abscess. In conclusion, the Ga-67 scan proved useful in the diagnosis of vascular graft infection, the definition of location of the extent of the disease and in the evaluation of the efficiency of treatment.     

111 In-labeled leukocytes in the detection of prosthetic vascular graft infections

Making a clinical diagnosis of infection in prosthetic vascular grafts is difficult but when undiagnosed, this condition has a high mortality rate. Using Indium-111-labeled white-blood cells, 30 scans were performed in 21 patients suspected of having a prosthetic graft infection. The diagnosis of infected graft was confirmed by surgery in all cases, and lack of infection was established by resolution of symptoms with conservative therapy. Twenty-four hour scans of autologous Indium-111 leukocytes were obtained, and correlative CT studies were done in 11 cases. There were 13 infected grafts at surgery (purulent material present), and scans were positive in all (100% sensitivity); of 17 scans, there were 15 true negatives and two false positives (88% specificity). Using the criteria of gas or fluid around the graft, the sensitivity of CT was only 37% in a small subset of these patients. One-half of the cases in which infection was suspected clinically had no infection and had negative scans. Various types of grafts and graft materials were used, and there was no correlation with presence or absence of infection on the basis of the type of graft. Extragraft infection sites were found in five patients. In conclusion, use of Indium-111 leukocytes has been found to be an accurate and valuable diagnostic method for evaluation of suspected prosthetic vascular graft infection, and to have higher diagnostic accuracy than CT.     

Sonography of axillofemoral and femorofemoral subcutaneous arterial bypass grafts

Axillofemoral and femorofemoral grafts in 12 patients were examined on 22 occasions with linear-array and digital static scanners with 5-MHz transducers and a 10-MHz high-resolution real-time instrument. Real-time instruments that produce a linear image, particularly high-resolution small-parts units, are the most appropriate to define the incorporation of the prosthesis, its pulsatility, and the nature of the perigraft bed. Early after implantation, these grafts have small perigraft fluid collections in the surgically created tunnels. These collections disappear spontaneously as the graft is incorporated into the tissues. However, discrete and persistent perigraft fluid collections are abnormal. Such collections were noted in five patients. One proved to be abscess and four were seromas. Graft occlusions (four patients) and an anastomotic aneurysm (one patient) were also readily diagnosed on sonography.     

Incorporation versus infection of retroperitoneal aortic grafts: MR imaging features

The magnetic resonance (MR) imaging characteristics of normal aortic graft healing were compared with those of perigraft infection in 57 patients after aortic graft implantation. Thirty-three patients without postoperative complications underwent MR imaging in a 0.35-T unit 1 week after graft implantation, and 13 of those patients were reexamined 2-3 months after graft implantation. Twenty-four patients with clinically suspected perigraft infection underwent MR imaging 6 weeks to 18 years after graft implantation. Early normal postoperative changes were characterized by a perigraft collar of low to medium signal intensity on T1-weighted images and of high intensity on T2-weighted images in all 33 cases, consistent with perigraft fluid collection. In 10 of 13 patients reexamined 2-3 months postoperatively, the MR images demonstrated a collar of tissue consistent with perigraft fibrosis. In cases of clinical suspicion of retroperitoneal graft infection, MR imaging showed eccentric fluid collections of low to medium signal intensity on T1-weighted images and high intensity on T2-weighted images at more than 3 months after surgery. The MR findings were diagnostic of retroperitoneal perigraft infection in 17 of 20 patients shown to be infected at surgery. Retroperitoneal infection was correctly excluded on the basis of MR findings in four patients. Thus, MR imaging is an accurate imaging method for the diagnosis of aortic graft infection. In the early postoperative phase, resolving perigraft fluid cannot be differentiated from perigraft infection.     

CT of aortoenteric fistulas

We compared CT findings with endoscopic, angiographic and surgical results in ten patients suspected of having an aortoenteric fistula (AEF) because of gastrointestinal bleeding (seven) or recurrent sepsis (three). CT correctly diagnosed AEF in six patients and excluded it in the other four. CT findings of AEF consisted of perigraft fluid (PGF) (5/6) and/or gas within the bed of the graft (4/6) later than three months after graft surgery. All six patients with AEF had perigraft infections; PGF with gas was found in 50%, PGF alone in 33%, and in one patient perigraft gas alone was found. Angiography and endoscopy failed to identify AEF. Our findings indicate that CT should be the initial imaging procedure in patients with suspected AEF who do not require immediate surgical intervention.     

Aortic aneurysmal disease: assessment of stent-graft treatment-CT versus conventional angiography

PURPOSE: To compare computed tomographic (CT) angiography and conventional angiography for determining the success of endoluminal stent-graft treatment of aortic aneurysms. MATERIALS AND METHODS: Forty patients underwent conventional angiography and CT angiography following treatment of aortoiliac aneurysms with endoluminal stent-grafts. Six additional sets of conventional angiographic-CT angiographic examinations were performed in five patients after placement of additional stent-grafts or coil embolization to treat perigraft leakage. Three faculty CT radiologists who were blinded to patient clinical data and outcome independently interpreted the CT angiograms, and three faculty angiographers, who were not involved in the stent-graft deployment, interpreted the conventional angiograms. Images were assessed for the presence of postdeployment complications. A reference standard was developed by experienced radiologists using all available images and clinical data. Sensitivities, specificities, and kappa values were calculated. RESULTS: Perigraft leakage was the most commonly identified complication. Twenty perigraft leaks were detected in the results of 46 examinations. Sensitivities and specificities for detecting perigraft leakage were 63% and 77% for conventional angiography and 92% and 90% for CT angiography, respectively. The kappa value was 0. 41 for conventional angiography and 0.81 for CT angiography. CONCLUSION: CT angiography is the preferred method for establishing the presence of perigraft leakage following treatment of aortoiliac aneurysms with stent-grafts.     

DSA and duplex sonography of aortic prostheses

In 95 patients with aortal grafts, DSA was compared with duplex ultrasonography. In 4 patients the graft was better visualized by means of angiography. Kinking, coiling, dilatations, pseudoaneurysms, stenoses, and occlusions could be sufficiently diagnosed with both methods. Marginal thrombosis and periprosthetic pathologies could only be found with ultrasonography. The ultrasonographic and angiographic examination techniques are described and the limitations of both methods discussed.     

64层螺旋CT在冠状动脉搭桥术后的应用价值

目的:探讨64层螺旋CT在冠状动脉搭桥术后的临床应用价值。方法:采用西门子Somatom Sensation Cardiac64螺旋CT对22例冠脉搭桥术后的患者(共计44根桥血管)进行了扫描,其中11例患者同时进行了冠状动脉造影检查。结果:64层螺旋CT显示22例患者发现44支桥血管,显示率100%。44支桥血管中,33支(75%)通畅、5支(11.4%)闭塞、3支(6.8%)中重度狭窄、3支(6.8%)轻度狭窄。与冠脉造影对照,诊断桥血管明显狭窄及闭塞的敏感性100%,特异性92.9%,阳性预测值87.5%,阴性预测值100%,准确率95.2%。结论:64层螺旋CT是评价桥血管闭塞及狭窄的可靠方法。     

Stent-graft placement for pseudoaneurysm of the aorta

PURPOSE: To evaluate the use of endovascular stent-graft placement to repair pseudoaneurysm of the aorta. METHODS: Six patients were treated with stent-grafts for pseudoaneurysms located in the thoracic aorta (n=2), thoracoabdominal aorta (n=3), and abdominal aorta (n=1). Etiologies of the pseudoaneurysms included leakage from surgical graft, penetrating atherosclerotic ulcer, pneumonia, perforated esophageal ulcer, and mycotic aneurysm. All patients were clinically considered to be at high surgical risk. RESULTS: Stent-grafts were successfully placed in all patients. There was one death in the perioperative period due to massive hemoptysis before stent-grafting. Two patients died of persistent infection. One patient with persistent perigraft leak died of rupture. Two other patients needed no further therapy for pseudoaneurysm. CONCLUSION: Stent-graft placement for pseudoaneurysm of the aorta can play the role of a temporizing method prior to surgical repair in high-risk cases and be a therapeutic alternative in cases without infection or perigraft leakage.     

Noninvasive evaluation of coronary artery bypass graft patency using three-dimensional angiography obtained with contrast-enhanced electron beam CT

OBJECTIVE: The purpose of this study was to determine the accuracy of three-dimensional coronary angiography obtained with electron beam CT in the assessment of the patency of coronary artery bypass grafts. SUBJECTS AND METHODS: Twenty-five patients who had undergone coronary artery bypass graft surgery were included. All patients underwent electron beam CT and conventional coronary angiography for the evaluation of the status of their bypass grafts. Three-dimensional reconstructions of the heart and bypass grafts were compared with selective angiographic images of the bypass grafts. RESULTS: Fifty-seven saphenous vein grafts and 22 left internal mammary artery grafts were evaluated for occlusion or patency. Sensitivity and specificity of electron beam CT in revealing left internal mammary artery patency were 80% and 82.4%, respectively. Sensitivity and specificity of electron beam CT in revealing saphenous vein graft patency were 91.7% and 91.1%, respectively. Sensitivity and specificity of electron beam CT for evaluating saphenous vein grafts according to coronary area were as follows: saphenous vein grafts to left anterior descending artery, 100% and 100%, respectively; to diagonal branch, 100% and 100%; to left circumflex artery, 100% and 88.9%; and to right coronary artery, 75% and 85.7%. CONCLUSION: Three-dimensional coronary angiography obtained with electron beam CT is a promising, useful, and relatively accurate diagnostic imaging technique for the evaluation of graft patency in patients who have undergone coronary artery bypass graft surgery.     

Coronary artery bypass grafts: ECG-gated multi-detector row CT angiography--influence of image reconstruction interval on graft visibility

PURPOSE: To evaluate the influence of different reconstruction intervals of retrospectively electrocardiographically (ECG)-gated multi-detector row computed tomographic (CT) angiography on image quality of different segments of various types of coronary artery bypass grafts. MATERIALS AND METHODS: Twenty consecutive patients with 62 grafts underwent retrospectively ECG-gated four-channel multi-detector row CT angiography and conventional coronary angiography. Raw helical CT data were reconstructed at 0%-90% of the cardiac cycle in increments of 10%. Each graft was separated into three segments (proximal segment, graft body, and distal anastomosis). Three graft types were identified according to site of distal anastomosis. Two readers assessed image quality of segments and graft types. Effective radiation dose was calculated. RESULTS: Best image quality of all segments was obtained at a reconstruction interval of 50%-70% of the cardiac cycle. Image quality of the proximal segment did not vary significantly with different reconstruction intervals (analysis of variance, P =.8), whereas image quality of the graft body and distal anastomosis changed significantly with varying reconstruction intervals (P <.001). Distal anastomosis and body of types 1 and 2 grafts were best seen at 60%-70% of the cardiac cycle, whereas distal anastomosis and body of type 3 grafts were best visualized at 50%. Accuracy of CT angiography for detection of graft patency was 94% for reader 1 and 95% for reader 2. Effective dose for CT was 11.4 mSv for both men and women. Mean effective dose for angiography was 2.1 mSv for men and women. CONCLUSION: Optimal selection of reconstruction interval improves image quality of the graft body and of distal anastomosis in particular.     

Surveillance of peripheral arterial bypass grafts with three-dimensional MR angiography: comparison with digital subtraction angiography

OBJECTIVE. The purpose of this study was to use contrast-enhanced three-dimensional MR angiography to assess the patency of peripheral arterial bypass grafts of the lower extremity. SUBJECTS AND METHODS. The study included 39 patients with 45 lower limb grafts. Twenty-eight were saphenous vein grafts, 13 were expanded polytetrafluoroethylene, and two were Dacron grafts. Digital subtraction angiography correlation was available for 30 patients (31 grafts). MR angiography was performed on a 1.5-T system with a multichannel quadrature phased array peripheral vascular coil. The scanning delay was determined with a test bolus technique, using half-time to maximum signal intensity in the graft. Arterial imaging was accomplished with two three-dimensional MR angiography acquisitions with gadopentetate dimeglumine administered using an automated injector. The pelvic and femoral arteries were imaged, the MR table was repositioned, and the lower limb arteries were imaged. The three-dimensional MR angiography sequence used the following parameters: TR/TE, 5.2/1.5 msec; inversion time, 28 msec; flip angle, 30 degrees. The proximal anastomosis, graft, and distal anastomosis were characterized as normal, stenosed, occluded, or ectatic or aneurysmatic. RESULTS. Sensitivity and specificity values for MR angiography regarding the assessment of grafts were 100% for 87 evaluable segments for which digital subtraction angiography correlation was available: stenosis (n = 10), occlusions (n = 9), ectasia or aneurysms (n = 8). Six segments could not be assessed because of the presence of intravascular stents or metallic clips. CONCLUSION. Contrast-enhanced three-dimensional MR angiography is well suited for the characterization of arterial grafts, for planning subsequent vascular interventions, and for excluding further lesions.     

双源CT冠状动脉成像评价冠状动脉搭桥术后桥血管通畅情况

目的探讨双源 CT 冠状动脉成像对冠状动脉搭桥术后桥血管通畅状况的诊断价值.资料与方法38例患者于冠状动脉搭桥术后行双源 CT 冠状动脉成像与冠状动脉造影检查,以冠状动脉造影作为“金标准”,对双源 CT 冠状动脉成像结果进行分析.结果38例患者共检出桥血管92支,其中内乳动脉桥31支,大隐静脉桥61支;31支内乳动脉桥中,26支(83.9%)桥血管通畅,5支(16.1%)管腔狭窄、闭塞;61支大隐静脉桥血管中35支(57.4%)桥血管通畅;26支(42.6%)管腔狭窄、闭塞.大隐静脉桥血管狭窄、闭塞的发生率明显高于内乳动脉桥血管(P<0.05).双源 CT 冠状动脉成像评价桥血管狭窄、闭塞的敏感性为93.9%,特异性为100.0%.结论双源 CT 冠状动脉成像对冠状动脉搭桥术后桥血管通畅状况的评价有较高的诊断价值,是一种快速、无创、准确、安全的检查方法.     

多层螺旋CTA:不同重建方法在主动脉瘤腔内隔绝术后的应用评价

目的：探讨多层螺旋CT血管造影不同重建方法在主动脉瘤腔内隔绝术后的临床应用价值。材料与方法：46例主动脉瘤腔内隔绝术后行多层螺旋CT血管造影，采用准直2.5mm，层厚3.0mm，螺距为6，重建方法为容积显示技术（volume rendering，VR）、表面阴影遮盖显示(shade surface display，SSD)及最大密度投影法（maximum intensity projection，MIP），并对三种方法进行比较。结果：46例中有1例术后内支架出现局限性断裂，VR及MIP均清晰显示了内支架的变化，SSD未能显示。1例内支架展开不良，三种重建方法均明确显示；6例术后出现渗漏，VR清晰显示渗漏的部位、形态及内漏量，MIP、SSD仅显示其中的5例，三者中以VR显示最佳。在显示支架内血流情况及瘤周血栓方面，VR能明确支架内有无血栓形成及腔内隔绝术后的转归变化，VR显示1例术后支架内血栓形成SSD及MIP未能显示。结论：多层螺旋CT能在较短时间内进行大范围的扫描，有利于主动脉病变的检查；VR图像优于SSD及MIP，能为术后内支架情况提供更多更准确的信息，VR技术应作为主动脉瘤内支架术后的首选三维重建方法。     

Diagnosis of synthetic vascular graft infection: comparison of CT and gallium scans

Sixteen patients were examined with both abdominal CT and 67Ga scintigraphy for suspected synthetic vascular graft infection. Two patients were studied twice, yielding a total of 18 paired tests. A total of 25 grafts were analyzed. The results of CT and 67Ga scintigraphy were compared for grafts in specific anatomic locations including the retroperitoneum, groin, and abdominal wall, and for combined sites. When all locations were considered as a group, CT had a sensitivity of 100% and specificity of 72%; 67Ga scintigraphy had a sensitivity of 78% and specificity of 94%. 67Ga scintigraphy proved to be more specific than CT (p less than .05) for combined sites, but no significant difference in sensitivities was demonstrated, possibly because of the small number of infected grafts in our study. No differences in sensitivities or specificities were statistically significant when grafts in individual anatomic sites were analyzed. Since no significant difference between the sensitivities of CT and 67Ga scanning was demonstrated in our study, although the number of infected grafts was small, CT is recommended as the initial examination when graft infection is suspected because it can be performed immediately. 67Ga scintigraphy remains an important complementary test, adding specificity to the diagnostic workup.     

Stent Graft Placement for Postsurgical Hemorrhage from the Hepatic Artery: Clinical Outcome and CT Findings

PurposeTo evaluate the clinical results and imaging follow-up findings of stent grafts placed for hemorrhage from hepatic arteries following surgery.Materials and MethodsThe investigation included 17 patients (14 men and 3 women) who underwent endovascular stent graft placement for hepatic arterial hemorrhage following surgery. Bleeding occurred from the common hepatic artery (n = 1; 6%), right hepatic artery (n = 1; 6%), proper hepatic artery (n = 6; 35%), and gastroduodenal artery stump (n = 9; 53%). Stent graft patency, thrombus at the graft, target hepatic artery diameter, and liver perfusion status were analyzed by comparing computed tomography (CT) scans performed before the procedure with follow-up CT scans. Laboratory data were also analyzed before the procedure and at follow-up intervals.ResultsThere were 17 stent grafts placed in 17 patients. The mean follow-up period was 356 days (range, 1–2,119 d). The stent graft primary patency rate was 79.5% at 1 month, 69.6% at 6 months, and 69.6% at 1 year. The clinical success rate was 82% (14 of 17 patients), and the technical success rate was 94% (16 of 17 patients). Mortality related to the stent graft was 12% (2 of 17 patients). Occlusion occurred in 4 of 16 stent grafts (25%). There was one technical failure. The mean stent graft diameter was 6.2 mm (range, 3.5–8.0 mm), and the degree of stent graft oversizing was 38% of the hepatic artery diameter on CT scans and 58% on angiography. Hepatic parenchymal perfusion was preserved in 80% of patients (12 of 15).ConclusionsHepatic artery hemorrhage following surgery can be treated effectively with stent graft placement.     

Pulsatile masses surrounding vascular prostheses: real-time US color flow imaging

A prospective evaluation of color flow mapping and real-time ultrasound was performed to determine if pseudoaneurysms could be distinguished from other causes of masses surrounding vascular grafts of the lower extremities. Twelve palpable pulsatile masses were imaged. Diagnoses were confirmed at angiography (n = 11), computed tomography (n = 7), aspiration biopsy (n = 5), and operative intervention (n = 6). A swirling pattern of blood flow was seen in six of seven cases of pseudoaneurysm. Lack of flow signals was noted in four of the five collections representing hematoma (n = 2) or infection (n = 2). The seventh case was later shown to be an infected, thrombosed pseudoaneurysm. The single false-positive diagnosis was made early in the series when the flow signals detected were due to transmitted arterial pulsations. The authors conclude that color Doppler flow imaging is useful in the differential diagnosis of pulsatile masses associated with prosthetic grafts. Prosthetic graft pseudoaneurysms have a specific appearance of swirling blood flow arising from a wide neck and are distinguishable from traumatic or iatrogenic pseudoaneurysms of the native vascular tree.