MRI versus helical CT for endoleak detection after endovascular aneurysm repair

OBJECTIVE: The objective of our study was to investigate the diagnostic accuracy of MRI and helical CT for endoleak detection. SUBJECTS AND METHODS: Fifty-two patients underwent endovascular aneurysm repair with nitinol stent-grafts. Follow-up data sets included contrast-enhanced biphasic CT and MRI within 48 hr after the intervention; at 3, 6, and 12 months; and yearly thereafter. The endoleak size was categorized as < or = 3%, > 3% < or = 10%, > 10% < or = 30%, or > 30% of the maximum cross-sectional aneurysm area. A consensus interpretation of CT and MRI was defined as the standard of reference. RESULTS: Of 252 data sets, 141 showed evidence for endoleaks. The incidence of types I, II, and III endoleaks and complex endoleaks was 3.2%, 40.1%, 8.7%, and 4.0%, respectively. The sensitivity for endoleak detection was 92.9%, 44.0%, 34.8%, and 38.3% for MRI, biphasic CT, uniphasic arterial CT, and uniphasic late CT, respectively. The corresponding negative predictive values were 91.7%, 58.4%, 54.7%, and 56.1%, respectively. The overall accuracy of endoleak detection and correct sizing was 95.2%, 58.3%, 55.6%, and 57.1% for MRI, biphasic CT, uniphasic arterial CT, and uniphasic late CT, respectively. CONCLUSION: MRI is significantly superior to biphasic CT for endoleak detection and rating of endoleak size, followed by uniphasic late and uniphasic arterial CT scans. MRI shows a significant number of endoleaks in cases with negative CT findings and may help illuminate the phenomenon of endotension. Endoleak rates reported after endovascular aneurysm repair substantially depend on the imaging techniques used.     

腹主动脉瘤腔内隔绝术后迟发型远端内漏Ⅱ期腔内治疗

目的：探讨腹主动脉瘤（AAA）腔内隔绝术EVE后迟发型远端内漏的Ⅱ期腔内治疗方法的价值。方法：为3例AAA EVE3年以后迟发型远端内漏患者进行了Ⅱ期延伸移植物置入治疗，2例经双侧动脉切开、两侧各置入1枚延伸移植物，1例经腹膜后径路和股动脉径路完成3枚延伸移植物置入。结果：3例均应用了贯穿导丝牵张技术，延伸移植物置入完成后均将内漏消除。结论：Vanguard支架-人造血管系统的结构特点可能是导致远期远端内漏的原因；延伸移植物是治疗的有效方法。导丝牵张技术有助于手术成功并节约手术时间。     

腹主动脉瘤腔内隔绝术中内漏动物模型的建立

目的：建立近似人体的腹主动脉瘤（AAA）腔内隔绝术（EVE）后内漏的实验动物模型。方法：采用6只犬 ，以牛颈静脉间置法或前壁补片的方法形成保留腰动脉的肾下型AAA，经髂动脉行AAA EVE，术中采用修剪人造血管和改变支架附着点的方法形成内漏。结果：血管造影示6只犬动脉瘤形态良好，5只犬形成了即时性内漏，内漏来自近端返流，也有近端返流。结论：通过移植物释放位置的变化可以模拟出与人体EVE后相似的即时性内漏，以供血流动力学和治疗研究。     

Ischemic skin ulceration complicating glue embolization of type II endoleak after endovascular aneurysm repair

The optimal treatment for type II endoleaks remains unclear. The present report describes a case of ischemic skin ulceration after glue embolization of a type II endoleak with challenging access in a multiply comorbid 82-year-old woman with an expanding aneurysm sac 3 years after endovascular aneurysm repair. Embolization was performed from a proximal position with an n-butyl cyanoacrylate/Ethiodol mixture to allow flow into the endoleak because direct sac puncture was hazardous. One week after intervention, an eschar, which progressed to superficial necrosis as a result of partial nontarget delivery of sclerosant, developed over the left iliac crest. The eschar was self-limiting, with complete resolution by 6 months.     

Role of the endothelial lining in endoleak formation and persistence after endovascular repair of aneurysm

PURPOSE: To evaluate whether ablation of the endothelial lining of an aneurysm can prevent endoleak persistence after endovascular aneurysm repair (EVAR). MATERIALS AND METHODS: Bilateral aneurysms were constructed in common iliac arteries in three different experimental groups. In group 1 (six dogs), 12 aneurysms without collateral outflow were created, the endothelial layer was removed on one side, and stent-grafts were implanted immediately after surgery with endovascular creation of a type I endoleak. In group 2 (six dogs), the same experiment was performed in aneurysms with collateral outflow. In group 3 (three dogs), six aneurysms with collateral outflow were denuded, but stent-grafts were implanted 3 months later. Follow-up imaging was performed with Doppler ultrasonography (US) and angiography until animal sacrifice 3 months after EVAR. Leak persistence and healing were also evaluated with macroscopic and histopathologic examination. RESULTS: Type I endoleaks persisted in all endothelialized group 1 aneurysms (six of six), but in none that were denuded before stent-graft implantation (P = .03). The ratio between the maximum diameter of the aneurysm measured before sacrifice and at baseline was significantly lower in denuded aneurysms than in aneurysms with an intact endothelial layer (74% vs 92%, P = .003). Endoleaks were observed in all aneurysms of groups 2 (denuded and intact endothelium) and 3. All endoleak areas were surrounded by endothelial lining. CONCLUSIONS: In this animal model of EVAR, ablation of the endothelial lining promotes long-term endoleak thrombosis after EVAR. The presence of collateral flow can promote re-endothelialization and endoleak persistence.     

Dual-energy computed tomography after endovascular aortic aneurysm repair: The role of hard plaque imaging for endoleak detection

Objectives

To assess the diagnostic accuracy of dual-energy computed tomography (DECT) for detection of endoleaks and aneurysm sac calcifications after endovascular aneurysm repair (EVAR) using hard plaque imaging algorithms.

Materials and methods

One hundred five patients received 108 triple-phase contrast-enhanced CT (non-contrast, arterial and delayed phase) after EVAR. The delayed phase was acquired in dual-energy and post-processed using the standard (HPI-S) and a modified (HPI-M) hard plaque imaging algorithm. The reference standard was determined using the triple-phase CT and contrast-enhanced ultrasound. All images were analysed separately for the presence of endoleaks and calcifications by two independent readers; sensitivity, specificity and interobserver agreement were calculated.

Results

Endoleaks and calcifications were present in 25.9 % (28/108) and 20.4 % (22/108) of images. The HPI-S images had a sensitivity/specificity of 54 %/100 % (reader 1) and 57 %/99 % (reader 2), the HPI-M images of 93 %/92 % (reader 1) and 96 %/92 % (reader 2) for detection of endoleaks. For detection of calcifications HPI-S had a sensitivity/specificity of 91 %/99 % (reader 1) and 95 %/97 % (reader 2), the HPI-M images of 91 %/99 % (reader 1) and 91 %/99 % (reader 2), respectively.

Conclusion

Using HPI-M, DECT enables an accurate diagnosis of endoleaks after EVAR and allows distinguishing between endoleaks and calcifications with high diagnostic accuracy.

Key Points

? Dual-energy computed tomography allows the diagnosis of aortic pathologies after EVAR. ? Hard plaque imaging algorithms can distinguish between endoleaks and aneurysm sac calcifications. ? The modified hard plaque imaging algorithm detects endoleaks with high diagnostic accuracy.     

介入法制作犬颅内动脉瘤模型

目的运用介入方法建立犬颅内动脉分叉部囊状动脉瘤模型。方法6条犬全麻后,采用血管内介入方法,用冠状动脉球囊导管扩张右颈总动脉近段,再用可脱球囊于扩张段远端将其栓塞,制作成6个分叉部动脉瘤。分别于术后1、2、3d行DSA检查并切除动脉瘤做病理组织学检查。结果6条犬成功获得6个动脉瘤模型。动脉瘤的平均宽度和平均长度在3d内逐渐减少。结论犬动脉瘤模型较好地模拟了人颅内动脉瘤大小、形态及DSA表现,可用于介入治疗新材料、新技术的实验研究。本动脉瘤模型的建立快速、可靠、可重复性强。     

Aortic side branch embolization before endovascular aneurysm repair: incidence of type II endoleak

PURPOSE: To assess the feasibility of embolization of aortic side branches and its impact on the incidence of type II endoleak after endovascular aneurysm repair. MATERIALS AND METHODS: Endovascular aneurysm repair was performed in 74 patients. Aortic side branch vessels were evaluated on the preoperative angiogram and computed tomography (CT) and, where embolization of lumbar and inferior mesenteric vessels was considered technically possible, this was attempted prior to endovascular repair. Follow-up CT was used to assess the presence of type II endoleak. RESULTS: Seventy-two patients were followed up for longer than 1 month. Embolization was attempted in 25 cases, successfully in 10, with partial success in 11, and failure in four. Twenty patients with successful or partly successful preoperative embolization were discharged and followed-up. Four (20%) had demonstrable type II endoleak during follow-up, with two of these persisting at latest follow-up. Of 43 patients without previous embolization, there were 10 (23.3%) type II endoleaks during the follow-up period, four of these persisting. In cases with type II endoleak, mean sac diameter change was -0.5 mm in the cases with previous embolization and +3.1 mm without. The mean period to onset of type II endoleak was 6.9 months without, and 15.3 months with, previous embolization. CONCLUSION: Although the cohort size is below a level that would confer significance, the trend of these findings is such as to suggest a lack of influence of aortic side branch embolization on the incidence of type II endoleak during the follow-up period.     

腹主动脉瘤腔内修复术后Ⅱ型内漏的栓塞治疗

内漏是腹主动脉瘤腔内修复术后并发症之一,本院血管外科应用钢圈栓塞治疗Ⅱ型内漏1例,就其经验总结如下. 患者为女性,81岁.于2006年4月24日因肾下腹主动脉瘤(图1)行腔内修复术,置入分叉型人工血管内支架(Zenith,Cook,USA),远端锚定于髂总动脉,保留两侧髂内动脉.患者恢复顺利,术后5 d出院.术后1年随访CTA显示支架形态位置满意,瘤腔内未见明显对比剂充盈,但瘤体直径与术前相比,无明显缩小(最大径仍为6 cm).2008年3月24日因下腹饱胀并扪及搏动性肿块1个月余来诊.     

The burden of hard atherosclerotic plaques does not promote endoleak development after endovascular aortic aneurysm repair: a risk stratification

Purpose  

To objectify the influence of the atherosclerotic burden in the proximal landing zone on the development of endoleaks after endovascular abdominal aortic aneurysm repair (EVAR) or thoracic endovascular aneurysm repair (TEVAR) using objective aortic calcium scoring (ACS).     

Transcatheter embolization of a type II endoleak after hybrid repair for thoracoabdominal aortic aneurysm

Hybrid stent-graft procedures with visceral revascularization have been reported as an alternative treatment option for thoracoabdominal aortic aneurysms (TAAAs), although the potential advantages of reduced morbidity and mortality compared with open surgical repair have not been definitively demonstrated. Endovascular aneurysm repair is associated with endoleaks in as many as 20% of cases in some series, often requiring repeat intervention. In the present case, during follow-up after a hybrid TAAA repair, a patient developed a type II endoleak originating from a celiac artery that was not ligated at its origin. The endoleak was successfully treated by transcatheter coil embolization.     

Time-resolved MR angiography for the classification of endoleaks after endovascular aneurysm repair

PURPOSE: To evaluate the utility of time-resolved MR angiography (TR-MRA), compared with digital subtraction angiography (DSA), in the classification of endoleaks in patients who have undergone endovascular aneurysm repair (EVAR). MATERIALS AND METHODS: Thirty-one patients who had undergone EVAR to repair an abdominal aortic aneurysm were evaluated with both TR-MRA and DSA to determine endoleak etiology. The patient population consisted of 26 men and 5 women with a mean age of 78.5 years (range, 55-93 years). The mean time interval between TR-MRA and DSA was 1.5 weeks (range, 1-8 weeks). Endoleaks were classified as type II when enhancement of the external iliac vessels was observed before the appearance of the endoleak; otherwise the endoleak was classified as type I or III. The results of TR-MRA classification were compared with the reference gold standard, DSA. RESULTS: Agreement between TR-MRA and DSA regarding endoleak classification occurred in 30 of 31 cases (97%). Discordant classification occurred in a case in which a Type II endoleak was misclassified as a Type III due to failure to visualize a lumbar vessel. CONCLUSION: TR-MRA is highly effective in classifying endoleaks following EVAR when compared with DSA.     

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.     

Clinical significance of endoleaks characterized by computed tomography during aortography performed immediately after endovascular abdominal aortic aneurysm repair: prediction of persistent endoleak

Purpose

This study aimed to predict the persistence of endoleaks (ELs) using patterns and volumes evaluated by computed tomography during aortography (CTDA) performed immediately after endovascular abdominal aortic aneurysm repair (EVAR).

Materials and methods

CTDA immediately after EVAR and at the 6-month follow-up CT were performed in 52 patients. ELs were classified as localized-type pattern (LTP; <180° around the center of the aneurysmal lumen) or circumferential-type pattern (CTP; >180°). The proportion of EL volume in the aneurysmal sac, excluding mural thrombus, was classified as grade A (≤5 %), B (5–10 %), or C (≥10 %). The 6-month follow-up residual rates were evaluated, and volume ratios (follow-up CT aneurysmal volume including mural thrombus/CTDA aneurysmal volume) were calculated.

Results

The residual rate (5.3 %) and mean volume ratio (83.9 %) of ELs with LTP were significantly lower than those of ELs with CTP (72.2 and 99.3 %, respectively); there was no significant difference in residual rate or mean volume ratio among EL grades (A: 17.6, 88.1 %; B: 55.6, 89.7 %; C: 54.5, 97.8 %).

Conclusion

ELs with LTP generally disappear over time after EVAR, with a concomitant reduction in aneurysm volume, whereas those with CTP persist, indicating that patients with EL with a CTP should be followed up carefully.