Low-dose multidetector-row CT-angiography of abdominal aortic aneurysm after endovascular repair

Purpose

To investigate the possibility of reducing radiation dose exposure while maintaining image quality using multidetector computed tomography angiography (MDCTA) with high-concentration contrast media in patients undergoing follow-up after endovascular aortic repair (EVAR) to treat abdominal aortic aneurysm.

Materials and methods

In this prospective, single center, intra-individual study, patients underwent two consecutive MDCTA scans 6 months apart, one with a standard acquisition protocol (130 mAs/120 kV) and 120 mL of iomeprol 300, and one using a low dose protocol (100 mAs/80 kV) and 90 mL of iomeprol 400. Images acquired during the arterial phase of contrast enhancement were evaluated both qualitatively and quantitatively for image noise and intraluminal contrast enhancement.

Results

Thirty adult patients were prospectively enrolled. Statistically significantly higher attenuation values were measured in the low-dose acquisition protocol compared to the standard protocol, from the suprarenal abdominal aorta to the common femoral artery (p < 0.0001; all vascular segments). Qualitatively, image quality was judged significantly (p = 0.0002) better with the standard protocol than with the low-dose protocol. However, no significant differences were found between the two protocols in terms of contrast-to-noise ratio (CNR) (13.63 ± 6.97 vs. 11.48 ± 8.13; p = 0.1058). An overall dose reduction of up to 74% was observed for the low-dose protocol compared with the standard protocol.

Conclusion

In repeat follow-up examinations of patients undergoing EVAR for abdominal aortic aneurysm, a low-dose radiation exposure acquisition protocol provides substantially reduced radiation exposure while maintaining a constant CNR and good image quality.     

Notes on the application of the Matsui-Kitamura stent-graft for endovascular repair of abdominal aortic aneurysm

Abdominal aortic and left common iliac aneurysms in a 79-year-old man who had undergone Miles' operation for rectal carcinoma were treated with endovascular repair of an abdominal aortic aneurysm (EVAR), taking into consideration the age, surgical history, and wishes of the patient and his family. The Matsui-Kitamura stent-graft (MK-SG) was designed based on preoperative angiographic mapping. At EVAR, the right leg of the MK-SG was caught at the aortic bifurcation because of unexpected contraction of the MK-SG. To resolve the problem, the body of the MK-SG was dilated with a balloon, slightly lifted while being gradually shortened, and eventually successfully connected to the leg of the MK-SG. Made of nitinol mesh, the MK-SG is stable and flexible enough to make it one of the best stent-grafts for EVAR. A serious drawback, however, is the high contraction rate of the MK-SG itself. It is difficult to estimate the appropriate length of the stent-graft owing to unpredictable contraction. It is important to understand its characteristics and to carefully design and acquire sufficient skills in manipulating MK-SG.     

腹主动脉瘤腔内修复术22例围手术期处理回顾性总结

目的 总结腹主动脉瘤腔内修复术(EVAR)围手术期处理的临床经验.方法 回顾分析22例腹主动脉瘤患者EVAR临床经过,通过术前对主要脏器功能进行评估和保护,CTA测量近远侧瘤颈长度、直径、角度和构型,瘤体与分支动脉的关系,最低肾动脉开口至腹主动脉分叉的距离,导入途径的直径、扭曲和钙化程度.根据CTA测量结果,选择覆膜支架和手术方式.术时采用局麻20例,中转全麻l例,1例通过髂总动脉重建导人途径采用硬膜外麻醉,1例合并Stanf.0rd A型主动脉夹层,术时采用全麻.在支架释放前准确定位最低肾动脉位置,至少保留一侧通畅的髂内动脉,若双侧需要覆盖,分期覆盖或髂内动脉重建.支架植入后复查造影,有无内漏.正确判断内漏类型并进行相应处理.支架近端Ⅰ内漏2例,球囊扩张1例,植入Cuff 1例;支架远端Ⅰ内漏1例,球囊扩张时,动脉破裂,行人工血管补片修补术;Ⅲ型内漏3例,球囊扩张后支架植入1例.1例合并Starford A型主动脉夹层先行胸主动脉腔内修复术,后行EVAR.术后7一10 d复查CTA,以后每年复查1次.结果 EVAR手术全获成功.主要并发症为单侧髂肢扭结继发血栓形成,Fogarty导管取栓并支架植人1例;腹壁切口裂开1例,清创缝合;无手术死亡,随访6个月～5年,患者均存活.结论 CTA图像质量高、测量准确,是EVAR术前评估和术后随访的金标准.EVAR是高危、高龄腹主动脉瘤患者有效的治疗方法.     

Endovascular treatment of endoleaks after endovascular abdominal aortic aneurysm repair: personal experience

PURPOSE: This paper describes the different endovascular treatments (cuffs, endografts and embolisation) available for types I, II and III endoleaks occurring after endovascular abdominal aortic aneurysm repair (EVAR). MATERIALS AND METHODS: From January 2000 to June 2006, 134 patients (118 men, 16 women; mean age 75.1 years) underwent EVAR. Ten patients (7%) developed significant endoleaks requiring endovascular treatment. RESULTS: Five endoleaks were type I, two were type II and three were type III. Of the five type I endoleaks, four were proximal and one was distal. The proximal endoleaks were treated by cuff deployment, whereas the distal endoleak was treated with a bifurcated graft. Of the two patients with type II endoleak, one was treated by translumbar puncture and coil embolisation, and the other was treated by superselective embolisation of the lumbar feeding vessel with nonresorbable particles. Of the three patients with type III endoleak, two were treated by deploying an aortouniiliac endograft inside the bifurcated graft and the other by implanting a cuff to restore continuity between the graft body and the contralateral limb. Endovascular treatment was successful in 6/10 cases, whereas three cases required surgical conversion. One patient did not undergo surgery owing to poor general condition. CONCLUSIONS: The reported incidence of endoleaks after EVAR is 10%-20%. Significant endoleaks should be treated promptly. Endovascular treatment can be done with different techniques, but success in not constant due to adverse anatomical conditions and technical difficulties.     

Renewed endovascular repair for recurrent acute abdominal aortic aneurysm

The aim of the study was to describe the successful endovascular management of a patient who was admitted urgently with a second episode of acute abdominal aortic aneurysm (AAA) 30 months after emergency endovascular abdominal aortic aneurysm repair (eEVAR) for a ruptured AAA. The patient, an 84 year-old male physician, presented with severe acute abdominal and back pain. Contrast-enhanced computer tomography scanning showed type III endoleak owing to complete disconnection of both graft limbs and the prosthetic main body. Treatment consisted of acute stent-grafting with two bridging stent-grafts to seal the endoleak and reline the graft. The patient is alive and well 6 months postoperatively. This case indicates the need for follow-up after eEVAR, but also that complications can be managed endovascularly.     

Complete ten-year follow-up after endovascular abdominal aortic aneurysm repair: survival and causes of death

Purpose

To analyze the hazard and causes of death after endovascular aneurysm repair (EVAR) of abdominal aortic aneurysms during a complete ten year follow-up.

Methods

This is a retrospective clinical study of 130 consecutive patients undergoing EVAR between 1995 and 1998. One-hundred twenty-one patients (93.1%) were treated with first-generation stentgrafts and nine patients (6.9%) received second-generation devices. All patients completed a follow-up of at least 10 years, unless death occurred before then. Time and causes of death were provided by the Austrian central register of deaths.

Results

The median follow-up was 7.6 years, and the 130 patients had 968.5 person-years of follow-up. The ten-year mortality rate was 62.3%. Cardiovascular events were the most frequent causes of death, with a 3.9 incidence rate per 100 person-years. Cancer death and death due to other causes occurred in 2.1 and 1.8 cases per 100 person-years, respectively. Lethal late aneurysm rupture happened in 4.6% (n = 6), which corresponds to an annual incidence rate of 0.6 per 100 person-years. All of those patients had been treated with first-generation devices.

Conclusions

Cardiovascular events were the most frequent cause of death after EVAR, followed by malignancy and other diseases. The risk of dying from secondary rupture was clearly lower than that of death due to other reasons during ten years after EVAR, even in patients with first-generation stentgrafts.     

Device migration after endovascular abdominal aortic aneurysm repair: experience with a talent stent-graft

PURPOSE: Device migration (DM) may cause late failure after endovascular aortic aneurysm repair (EVAR). Computed tomography (CT) scans following EVAR were reviewed to establish the frequency of DM and whether it can be predicted. MATERIALS AND METHODS: Fifty-five patients underwent EVAR with a Talent stent-graft with suprarenal fixation. CT with a fixed protocol was performed at regular intervals. Patient demographics, risk factors, procedure details, and follow-up events were reviewed. Two observers, blinded to each other, reviewed axial images and mutliplanar reformats of the CT scans. DM was defined as a change of > or = 10 mm in the distance between a reference vessel (celiac axis/superior mesenteric artery) and the proximal device. Follow-up was performed for a minimum of 2 years (mean, 3 years; range, 2-5 years). RESULTS: DM was detected in six of 38 patients (15.8%) by 2 years. There were no new cases of migration in the 19 patients at 3 years but one new case in the six patients at 4 years (16.6%). Mean migration over 2 years was 4.8 mm +/- 4.2 mm. One patient with DM developed a type I endoleak that required reintervention. This patient developed a further endoleak and died following surgery for rupture. Top neck enlargement was the only predictive factor identified, present in 71% of patients with DM (P = .056). CONCLUSION: DM occurred in a small proportion of patients; closer follow-up intervals may be necessary in patients with short/enlarging proximal necks.     

Analysis of initial CT findings after endovascular repair of abdominal aortic aneurysm.

PURPOSE: To determine the spectrum and frequency of specific computed tomographic (CT) findings in the acute period after endovascular repair of abdominal aortic aneurysm (AAA). MATERIALS AND METHODS: CT images obtained 1--3 days after endograft placement were evaluated in 88 patients. The images were analyzed for stent position, appearance of endograft components, perigraft leak, and postoperative findings including air and acute thrombus within the aneurysm and air surrounding the femoral-femoral bypass graft. Findings that could be misinterpreted as perigraft leak were evaluated. RESULTS: Fifteen (17%) of 88 patients had perigraft leak in the acute postoperative period. The bare segment of the proximal self-expanding stent covered one or both renal arteries in 54 (61%) patients. One patient had CT evidence of renovascular compromise. Postoperative air was within the aneurysmal sac in 51 (58%) patients and surrounded the femoral-femoral bypass graft in 67 (94%) of 71 patients in whom the grafts were evaluated with CT. Mottled attenuation within the aneurysmal sac was seen in 50 (57%) patients. Forty-six (52%) patients had calcifications within longstanding thrombus. In 31 (35%) patients, findings that could have been misinterpreted as perigraft leak were identified. CONCLUSION: Accurate analysis of CT findings after endovascular AAA repair requires careful review of all available CT images (preprocedural and pre- and postcontrast) and clear understanding of specific stent-graft components and placement.     

Renal dysfunction after abdominal or thoracic endovascular aortic aneurysm repair: incidence and risk factors

Purpose

To determine the incidence and risk factors of renal dysfunction after abdominal endovascular aortic repair (EVAR) and thoracic endovascular aortic repair (TEVAR).

Materials and methods

The study consisted of 227 patients treated with EVAR and 90 with TEVAR for aortic aneurysms. Parameters, including patients’ background factors, preoperative renal function, contrast dose and aortic wall irregularity on CT images were assessed in relation to postoperative renal dysfunction.

Results

Deterioration of renal function was observed in 33 of 218 patients (15.1%) after EVAR and in 7 of 79 (8.9%) patients after TEVAR. Hemodialysis was required in one patient after EVAR. In EVAR, renal dysfunction correlated with age (p = 0.034) and occlusion of accessory renal artery (p = 0.0001). In TEVAR, renal dysfunction correlated with age (p = 0.021), contrast dose (p = 0.042) and irregularity of the descending aortic wall (p = 0.023). In a multiple regression analysis, postoperative renal dysfunction was correlated with occlusion of accessory renal artery (p = 0.0003) after EVAR, and age (p = 0.02), contrast dose (p = 0.026) and irregularity of the descending aortic wall (p = 0.042) after TEVAR.

Conclusion

Occlusion of accessory renal artery in EVAR, and age, contrast dose and irregularity of the descending aortic wall in TEVAR were considered to be predictors of postoperative renal dysfunction.

     

采用血管缝合器治疗复杂型腹主动脉瘤腔内隔绝术一例

腹主动脉瘤腔内修复术(TEVAR)常规采用双侧股动脉切开途径置入.我们采用血管缝合器顺利完成1例复杂型TEVAR,现报道如下.患者男,56岁.既往有10年高血压、糖尿病及糖尿病肾病史,行口服药物治疗.3年前发现腹部搏动性包块,CT确诊断为肾下型腹主动脉瘤,当时测得瘤体最大径约35 mm.     

腹主动脉瘤腔内隔绝术后神经缺血性损伤

目的：探讨在腹主动脉瘤（AAA）腔内隔绝术（EVE）中神经缺血性损伤的发生原因及防治。临床资料：我科在施行AAA EVE中遇到1例术后发生神经缺血性损伤。患者为Ⅱa型AAA，选用Talent分叉型移植物行EVE，手术顺利。术后出现双侧股部酸痛不适、乏力，伴右侧屈髋无力。行肌电图检查提示双侧腓总神经、胫神经、H反射传导速度均减慢，双侧股神经未能引出动作电位。给予甲钴胺0.5mg肌内注射，隔日1次，地巴唑10mg3次/d，并辅以高压氧治疗和股四头肌功能锻炼。治疗2个月后患者股部疼痛、乏力逐步缓解，无明显功能障碍。复查下肢肌电图无明显改善。结论：AAA EVE后可能会发生脊髓的缺血性损伤，但发生率很低，术中封闭腰动脉是导致脊髓缺血的原因。脊髓缺血性损伤早期治疗最为重要，后期的神经营养治疗和功能锻炼也可以改善部分症状。     

Risk factors associated with late aneurysmal sac expansion after endovascular abdominal aortic aneurysm repair

PURPOSE

We aimed to identify the risk factors associated with late aneurysmal sac expansion after endovascular abdominal aortic aneurysm repair (EVAR).

METHODS

We retrospectively reviewed contrast-enhanced computed tomography (CT) images of 143 patients who were followed for ≥6 months after EVAR. Sac expansion was defined as an increase in sac diameter of 5 mm relative to the preoperative diameter. Univariate and multivariate analyses were performed to identify associated risk factors for late sac expansion after EVAR from the following variables: age, gender, device, endoleak, antiplatelet therapy, internal iliac artery embolization, and preprocedural variables (aneurysm diameter, proximal neck diameter, proximal neck length, suprarenal neck angulation, and infrarenal neck angulation).

RESULTS

Univariate analysis revealed female gender, endoleak, aneurysm diameter ≥60 mm, suprarenal neck angulation >45°, and infrarenal neck angulation >60° as factors associated with sac expansion. Multivariate analysis revealed endoleak, aneurysm diameter ≥60 mm, and infrarenal neck angulation >60° as independent predictors of sac expansion (P < 0.05, for all).

CONCLUSION

Our results suggest that patients with small abdominal aortic aneurysms (<60 mm) and infrarenal neck angulation ≤60° are more favorable candidates for EVAR. Intraprocedural treatments, such as prophylactic embolization of aortic branches or intrasac embolization, may reduce the risk of sac expansion in patients with larger abdominal aortic aneurysms or greater infrarenal neck angulation.The aim of endovascular abdominal aortic aneurysm repair (EVAR) is to prevent rupture of an abdominal aortic aneurysm (AAA) by depressurizing the aneurysm and excluding it from the systemic circulation using a stent-graft. Aneurysmal sac reduction is a reliable marker for the long-term prognosis after EVAR. Although most aneurysmal sacs shrink after EVAR, some sacs continue to expand. A relationship between aneurysm size and endoleaks was previously reported (1, 2). Most type II endoleaks spontaneously disappear over time, but 10%–25% persist for more than six months after EVAR (3–6). Persistent endoleaks with aneurysmal sac expansion are at high risk of rupture because of the continuously elevated intra-aneurysmal pressure and require a second intervention, such as embolization (7–11). However, it is difficult to predict sac expansion and persistent endoleak before performing EVAR. Although intraoperative intrasac thrombin injection and prophylactic embolization of aortic branches such as the inferior mesenteric artery and lumbar artery are reported to reduce the incidence of type II endoleak, the efficacy and clinical benefit of these procedures in terms of late postoperative aneurysm shrinkage have not been fully evaluated (12–15). Therefore, the purpose of this study was to identify the risk factors associated with late aneurysmal sac expansion after EVAR to determine possible indications for intrasac embolization and prophylactic embolization of aortic branches.     

Prediction of deformations during endovascular aortic aneurysm repair using finite element simulation

During endovascular aortic aneurysm repair (EVAR), the introduction of medical devices deforms the arteries. The aim of the present study was to assess the feasibility of finite element simulation to predict arterial deformations during EVAR. The aortoiliac structure was extracted from the preoperative CT angiography of fourteen patients underwent EVAR. The simulation consists in modeling the deformation induced by the stiff wire used during EVAR. The results of the simulation were projected onto the intraoperative images, using a 3D/2D registration. The mean distance between the real and simulated guidewire was 2.3 ± 1.1 mm. Our results demonstrate that finite element simulation is feasible and appear to be reproducible in modeling device/tissue interactions and quantifying anatomic deformations during EVAR.     

Aneurysmal sizing after endovascular repair in patients with abdominal aortic aneurysm: interobserver variability of various measurement protocols and its clinical relevance

The aim of this study was to determine the variability of various measurement protocols for measurement of abdominal aortic aneurysm (AAA) and the clinical relevance of variability. Three radiologists performed computed tomographic angiography measurements of both the aorta and the largest portion of the aneurysm on selected axial slices. Then measurements of the largest portion of the aneurysm were performed on unselected axial slices, sagittal and coronal reformatted. Finally, aortic volume was calculated. Measurements and volume calculation were performed before and after endovascular repair and assessed: Part 1: interobserver variability for maximum anteroposterior (MAP) and maximum transverse (MTR) diameters on selected slices; part 2: interobserver variability for unselected slices considering MAP and MTR; part 3: interobserver variability considering maximum diameter in any direction (MAD); part 4: interobserver variability for sagittal (SAG) and coronal (COR) free curved multiplanar reformation (MPR); and part 5: volume calculations. We then determined which technique of measurement was the most clinically relevant for detecting changes in aneurysm size or aortic volume. Parts 1 and 2: interobserver variability was 4.1 mm for both MAP and MTR; part 3: interobserver variability was 7 mm for MAD; part 4: interobserver variability was 5.5 mm (COR) and 4.9 mm (SAG); part 5: interobserver variability for volume was 5.5 ml. A combination of MAP and MTR was the most useful for detecting aortic modification. Volume calculation was needed in only a few cases. We recommend avoiding MAD and MPR measurements and suggest instead measuring both maximum anteroposterior and maximum transverse diameters. If aneurysm size remains stable after endovascular repair, aneurysm volume should be measured.