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Type II endoleak is a common condition occurring after endovascular repair of abdominal aortic aneurysms (EVAR), and may result in aneurysm sac growth and/or rupture in a small number of patients. A prophylactic strategy of inferior mesenteric artery (IMA) embolization before EVAR has been advocated, however, the benefits of this strategy are controversial. A clinical vignette allows the authors to summarize the available data about this issue and discuss the possible benefits and risks of prophylactic IMA embolization before EVAR. The authors performed a meta-analysis of available data which showed that the pooled rate of type II endoleak after IMA embolization was 19.9% (95% CI 3.4–34.7%, I2 93%) whereas it was 41.4% (95% CI 30.4–52.3%, I2 76%) in patients without IMA embolization (5 studies including 596 patients: p < .0001, OR 0.369, 95% CI 0.22–0.61, I2 27%). Since treatment for type II endoleaks is needed in less than 20% of cases and this complication can be treated successfully in 60–70% of cases resulting in an aneurysm rupture risk of 0.9%, these data indicate that embolization of patent IMA may be of no benefit in patients undergoing EVAR.
A 67 year old man presents with a growing infrarenal abdominal aortic aneurysm. He has been a heavy smoker, has a history of myocardial infarction 2 years ago, and suffers from moderate renal impairment. The pre-operative CT angiogram reveals a favorable anatomy for EVAR but shows a relatively large and patent inferior mesenteric artery. Should I coil this artery during or before EVAR?
Type II endoleak is a common condition occurring after endovascular repair of abdominal aortic aneurysms (EVAR). It is the result of retrograde blood flow into the aneurysm sac from patent aortic vessels such as the inferior mesenteric artery (IMA), the lumbar arteries, and the median sacral artery through collateral circulation.
Type II endoleak is considered the least severe type of endoleak occurring after EVAR. Still, in a small number of patients, type II endoleak may result in aneurysm sac growth and/or rupture. Since the treatment of this endoleak is sometimes technically difficult with suboptimal results,
Strategies to reduce the rate of type II endoleaks: routine intra-operative embolization of the inferior mesenteric artery and thrombin injection into the aneurysm sac.
Prospective comparative analysis of colour-Doppler ultrasound, contrast enhanced ultrasound, computed tomography and magnetic resonance in detecting endoleak after endovascular abdominal aortic aneurysm repair.
of such leaks resolve spontaneously within the first 6 months of the operation and no treatment is indicated. However, a minority of type II endoleaks persist or others may appear later on, and this may cause concern regarding their impact on the fate of the aneurysm sac.
Studies regarding the significance of type II endoleak have shown contradictory results. Some studies have shown that type II endoleaks are associated with a benign course.
However, most studies are in agreement that type II endoleak may result in persistently elevated intra-sac pressure and failure of aneurysm sac shrinkage.
A few studies concluded that persistent type II endoleak is associated with adverse outcomes such as aneurysm sac growth and rupture and therefore requires re-intervention.
About 35% of these endoleaks resolved spontaneously. Three hundred and ninety three (26%) interventions for type II endoleak were performed with a success rate of 71.5%. Fourteen patients (0.9%) with isolated type II endoleak had ruptured abdominal aortic aneurysm, six of them without any sign of aneurysm sac growth. Another meta-analysis
was not able to define a threshold for treatment of type II endoleak as the aggressive treatment of type II endoleak not associated with sac expansion did not provide better results than a more conservative strategy (intervention only in cases of type II endoleak with sac expansion > 5 mm or persistent type II endoleak for > 12 months). No aneurysm rupture occurred in this pooled series. However, type II endoleak associated with an aneurysm sac growth ≥ 10 mm is considered an indication for endovascular, laparoscopic or open repair.
Impact of Inferior Mesenteric Embolization Prior to Evar in Preventing Type II Endoleak
Although EVAR has been performed for almost three decades, there are only five studies adequately comparing the outcome of IMA embolization with a conservative strategy.
Pre-operative inferior mesenteric artery embolization before endovascular aneurysm repair: decreased incidence of type II endoleak and aneurysm sac enlargement with 24-month follow up.
The results of these series have been pooled here using the random effects method. Statistical analysis was performed using Open meta-analysis statistical software (http://www.cebm.brown.edu/open_meta). These five studies reported on 246 patients who underwent IMA embolization with or without embolization of patent lumbar arteries and their outcome was compared with that of 350 patients with patent IMA and who did not undergo prophylactic embolization of the aortic branches. Two studies performed IMA embolization with Amplazer
Pre-operative inferior mesenteric artery embolization before endovascular aneurysm repair: decreased incidence of type II endoleak and aneurysm sac enlargement with 24-month follow up.
In a few cases, embolization of lumbar arteries was performed as well. The embolization procedure had a success rate of 98.4% (95% CI 96.3–100%). The rate of type II endoleak after IMA embolization was 19.9% (95% CI 3.4–34.7%, I2 93%) whereas it was 41.4% (95% CI 30.4–52.3%, I2 76%) in patients without IMA embolization (p < .0001, OR 0.369, 95% CI 0.222–0.613, I2 27%) (Fig. 1). Lumbar arteries were responsible for type II endoleak in a few patients.
Pre-operative inferior mesenteric artery embolization before endovascular aneurysm repair: decreased incidence of type II endoleak and aneurysm sac enlargement with 24-month follow up.
reported on the number of patients who required re-intervention for type II endoleak and this was significantly lower after IMA embolization (1.2% vs. 13.4%, p < .0001, OR 0.091, 95% CI 0.027–0.301, I2 0%). However, the threshold for intervention varied significantly between studies. Two studies reported on aneurysm related mortality, which was nil in both.
Pre-operative inferior mesenteric artery embolization before endovascular aneurysm repair: decreased incidence of type II endoleak and aneurysm sac enlargement with 24-month follow up.
Pre-operative inferior mesenteric artery embolization before endovascular aneurysm repair: decreased incidence of type II endoleak and aneurysm sac enlargement with 24-month follow up.
the overall linearized aneurysm shrinkage rate was 1.4 ± 3.8 mm per year in the IMA embolization group and 1.7 ± 2.4 mm per year in the control group (p < .72).
Figure 1Forest plot showing the impact of pre-operative inferior mesenteric artery (IMA) embolization versus conservative treatment on the development of type II endoleak in patients with patent IMA undergoing endovascular repair of abdominal aortic aneurysm.
observed that the diameter of the proximal IMA was larger than 2.5 mm in 24% (26/106) of patients without type II endoleak, in 50% of those with transient endoleak (5/10), and 100% (5/5) in patients with persistent endoleak. In multivariate analysis, the absence of stenosis of the IMA at its orifice was more likely to be a significant factor of persistent type II endoleak (p = .0003), and thrombus at the orifice of the IMA was a negative predictor of persistent type II endoleak (p = 0.043).
confirmed these findings and showed that an IMA diameter > 2.5 mm along with each additional patent lumbar artery ≥ 1.9 mm were predictors of permanent type II endoleak. Similarly, Müller-Wille and colleagues
observed that patients without complex IMA and lumbar artery type II endoleak in whom the largest feeding and/or draining artery was larger than 3.8 mm, and patients with a complex IMA type II endoleak in whom the largest feeding and/or draining artery was larger than 2.2 mm were at high risk for aneurysm sac enlargement.
Another study showed the significant association between the diameter of the IMA and the occurrence of type II endoleak.
Identification of predictive CT angiographic factors in the development of high risk type 2 endoleaks after endovascular aneurysm repair in patients with infrarenal aortic aneurysms.
However, multivariate analysis showed that the number and diameter of patent lumbar arteries were the only predictors of permanent type II endoleak requiring treatment.
Identification of predictive CT angiographic factors in the development of high risk type 2 endoleaks after endovascular aneurysm repair in patients with infrarenal aortic aneurysms.
Potential Adverse Events Associated with Inferior Mesenteric Artery Embolization
A few serious complications have been reported after embolization of the IMA. Post-operative death secondary to colonic ischemia has been reported as a result of catheter directed embolization of the IMA prior to EVAR
Strategies to reduce the rate of type II endoleaks: routine intra-operative embolization of the inferior mesenteric artery and thrombin injection into the aneurysm sac.
Pre-operative inferior mesenteric artery embolization before endovascular aneurysm repair: decreased incidence of type II endoleak and aneurysm sac enlargement with 24-month follow up.
Colonic necrosis subsequent to catheter-directed thrombin embolization of the inferior mesenteric artery via the superior mesenteric artery: a complication in the management of a type II endoleak.
Pre-operative inferior mesenteric artery embolization before endovascular aneurysm repair: decreased incidence of type II endoleak and aneurysm sac enlargement with 24-month follow up.
However, considering the current clinical practice in which type II endoleaks are actively treated only in case of aneurysm growth, it is evident that routine pre-operative IMA embolization is not cost-effective.
The present patient is rather young, but has a history of myocardial infarction and of moderate renal failure, which may increase his operative and late mortality risk.
Identification of predictive CT angiographic factors in the development of high risk type 2 endoleaks after endovascular aneurysm repair in patients with infrarenal aortic aneurysms.
Colonic necrosis subsequent to catheter-directed thrombin embolization of the inferior mesenteric artery via the superior mesenteric artery: a complication in the management of a type II endoleak.
If it is assumed that his moderate renal insufficiency is equivalent to a creatinine serum level > 150 μmol/L, the Glasgow Aneurysm Score would be 88. According to the Eurostar registry data, the 30 day mortality risk of this patient would be about 5% and his 6 year survival would be about 60%.
Such a high operative risk suggests that he most certainly would benefit from a straightforward EVAR without IMA embolization. This strategy would also prevent any further risk of acute kidney injury possibly associated with the use of a larger amount of contrast.
There are a few data showing that smoking habit is associated with a lower risk of type II endoleak after EVAR.
Such a lower risk of endoleak can be related to the decreased perfusion of the IMA and lumbar arteries in previous and current smokers compared with non-smokers.
Indeed, universal atherosclerosis in heavy smokers may affect the visceral arteries and impair the retrograde collateral circulation to the aneurysm sac. Since this patient has been a heavy smoker, it may be expected that his risk of developing a type II endoleak secondary to a patent IMA is significantly reduced.
Pooled analysis of available data indicates that IMA embolization is associated with significantly lower risk of type II endoleak, but the pooled rate of this event is still about 20% among these patients and other aortic branches may be responsible for endoleak. Therefore, type II endoleak cannot be prevented in all patients solely by IMA embolization. Indeed, large lumbar arteries are associated with the occurrence of type II endoleak,
Identification of predictive CT angiographic factors in the development of high risk type 2 endoleaks after endovascular aneurysm repair in patients with infrarenal aortic aneurysms.
Therefore, accurate imaging evaluation of the lumbar arteries is needed to better estimate the real value of IMA embolization when a large number of lumbar arteries are patent.
Since treatment for type II endoleaks is needed in less than 20% of cases and this complication can be treated successfully in 60–70% of cases,
Strategies to reduce the rate of type II endoleaks: routine intra-operative embolization of the inferior mesenteric artery and thrombin injection into the aneurysm sac.
Prospective comparative analysis of colour-Doppler ultrasound, contrast enhanced ultrasound, computed tomography and magnetic resonance in detecting endoleak after endovascular abdominal aortic aneurysm repair.
Pre-operative inferior mesenteric artery embolization before endovascular aneurysm repair: decreased incidence of type II endoleak and aneurysm sac enlargement with 24-month follow up.
Identification of predictive CT angiographic factors in the development of high risk type 2 endoleaks after endovascular aneurysm repair in patients with infrarenal aortic aneurysms.
Colonic necrosis subsequent to catheter-directed thrombin embolization of the inferior mesenteric artery via the superior mesenteric artery: a complication in the management of a type II endoleak.
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