Endoleaks are defined as persistent blood flow outside the lumen of the endograft but within the aneurysm sac, as verified by imaging study.[1] Endoleaks can be classified according to Veith et al.[2]
Type I | Inadequate sealing of landing zones
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Type II | Retrograde blood flow in the aneurysm sac via collateral vessels (mainly nferior mesenteric artery and lumbar arteries, occasionally accessory renal artery)
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Type III |
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Type IV | Generally porous graft (intentional design of graft, usually self-limiting) |
Type V | Endotension (growing aneurysm without evidence of endoleak) |
Endoleaks can be subdivided into three groups based on when they manifest.[3]
- Early endoleak: within 24 hours
- Intermediate endoleak: postinterventional day 1 to 90.
- Late doleak: after 90 days
Type Ia endoleak
With type I endoleaks, there is a significant increase in pressure in the aneurysm sac with a corresponding risk of rupture. The incidence of type 1a endoleaks increases with::
- Short aneurysm neck (<15 mm)
- Wide neck diameter (>32 mm)
- Aaneurysm neck with distal enlargement
- Increased angulation (>60°)
- Calcification and thrombus material in the landing zones
If possible, type I endoleaks should therefore be repaired before patients leave the OR [5, 6], although this is not always possible. In a cohort study by the Vascular Study Group of New England (VSGNE), 80 (3.3%) of 2402 patients who underwent elective EVAR had persistent endoleak type I.[6] Patients with type I endoleak suffered higher in-hospital mortality compared with others but did not differ in their 1-year mortality, and in 94% of cases, the endoleak had resolved within 1 year without intervention. Similar experiences have been reported from other studies.[7] If interventional repair in endoleak type I is not successful, the above data suggest that watchful waiting is an option, but patients must be carefully followed up. Any increase in size of the aneurysm sac can be followed by ultrasonography if suitable expertise is available; a follow-up interval of three months appears to be adequate.
Early type I endoleaks can undergo balloon remodeling, and so-called extension cuffs and bare metal stents may also be used. There is also the endoluminal option of pinning stent graft components to the vessel wall with staples or endo-anchors.[8]
In late phases with persistent type I endoleak, an attempt can be made to fill the lumen between the endograft and arterial wall by embolization. If the aneurysm diameter continues to grow, extension of the proximal or distal landing zone by stent graft or open surgery may be considered.
Type II endoleak
There is a systematic review of the significance of type II endoleaks based on 32 nonrandomized retrospective studies involving 21,744 patients.[9] Type II endoleaks were observed in 10.2% of patients after EVAR, and spontaneous regression was seen in 35.4% of cases. Aneurysm rupture was seen in 14 patients (0.9%) with isolated type II endoleak, although in 6 of these patients the aneurysm had not expanded. Out of 393 interventions for type II endoleaks, 28.5% were unsuccessful. The authors of this review article concluded that nonsurgical management of type II endoleak is safe, which is in line with data from other studies.[10] Another systematic review did not identify a cutoff point at which type II endoleaks require intervention.[11] Considering the uncommon nature of aneurysm sac enlargement and rupture in type II endoleak, it is considered a "benign complication" with treatment decisions on a case-by-case basis. A retrospective study from 2014 also came to this conclusion.[12]
Large caliber lumbar arteries can result in type II endoleaks [13] as can a large inferior mesenteric artery. Endoleak management can include embolization of the above-mentioned vessels via microcatheters. After EVAR, the inferior mesenteric artery is accessed via the arc of Riolan with probing of the superior mesenteric artery; the lumbar arteries are accessed via the collateral circulation from the internal iliac artery. Eembolization often has to be repeated, because after occlusion of the vessels, other collateral vessels may develop. If arterial access is not available, therapy may also proceed by direct puncture of the aneurysm sac and localization of the endoleak (from posterior under local anesthesia). [14] Minimally invasive stapler transection of the inferior mesenteric artery is another treatment option. The success rate of interventional management in type II endoleaks is 60% to 80%. Surgical treatment is indicated if the feeder vessels cannot be disrupted by interventional measures and an increase in size is observed.
Type III endoleak
The incidence of type III endoleaks is less than 4% at 1-year follow-up.[15, 16] Leakage is associated with an increased risk of rupture and should be treated promptly.[17] Repair is effected by endoluminal lining all or part of the endograft with a second endograft. The same also applies to the disconnection of individual stent graft components. Open surgical repair is rarely required.
Type IV endoleak
Type IV endoleaks result from endograft porosity or leakage. Typically, toward the end of the intervention, the leaks present as a perigraft contrast cloud persisting for several seconds during the final verification angiogram.[17] In most cases, the leaks resolve within 24 hours once the heparin effect wears off. Persistent type IV endoleaks generally do not require treatment.[18] In case of unexpected progressive aneurysm growth, internal stenting ("relining") of the endograft becomes necessary.
Type V endoleak
In this endoleak type, also known as endotension, there is a continuous increase in the size of the aneurysm sac with no apparent contrast leakage. Usually, these endoleaks are self-limiting. An increase in size and imminent rupture require reintervention, either by implanting a second endograft within the first endoluminal graft or by open surgical repair.