Author: Philippe Ayres, MD
Editor: Nicole Anthony, MD
Introduction:
Since the 1990s, EVAR (endovascular aortic repair) has largely replaced open repair of abdominal aortic aneurysms (AAA). Although there is a lower associated, perioperative 30-day all-cause mortality and morbidity when compared to open surgery, EVAR still carries a 25% to 30% rate of post-op complications.[1] As such, AAA repair complications should be in the differential diagnosis in patients with a known history of AAA repair. The presenting signs and symptoms of EVAR complications vary based on the type, so there isn’t a perfect “one size fits all” presentation for these patients. Instead, I find it helpful to break up EVAR complications into two categories: systemic and localized complications. This now lends itself nicely to two separate blog posts. This post will focus on systemic complications while the second will discuss localized complications. So let’s go ahead and get right into it with a case!
Figure 1. The femoral artery approach to insertion of stent graft
Figure 2. (A, B) Different iterations of internal iliac artery directional branched stent graft systems. (C, D) The current version. [7]
Case:
It’s 6:45am. You’ve had a good night’s sleep, drank your coffee, and got pumped on your way to work as you listened to the Queen–yes, I mean Rihanna, not Beyonce. (I know. Hot take.) As you open the board, you “chart-check” the first patient waiting to be seen: 82-year-old male with worsening right lower extremity pain for 3 days. The pain is diffuse and aching in nature and worsens with walking. He has a past medical history of hypertension, hyperlipidemia, diabetes and abdominal surgery many years ago. Of course, there are no records available regarding this mystery surgery.
The vital signs are unremarkable. The physical exam is notable for pain with passive flexion of the right knee, notably over the anterior thigh. The patient has 5/5 strength in bilateral upper and lower extremities, cranial nerves 2-12 are intact, sensation to light touch is intact in the bilateral upper and lower extremities, coordination and gait are intact although limited secondary to an obvious limp. He has 2+ dorsalis pedis and posterior tibial pulses bilaterally. The abdomen is soft, non-distended, and non-tender. No mass is palpated. He reports pain when ambulating, repeatedly insisting that he is “fine” and that he only came due to his wife’s insistence. Given that the patient is well-appearing and neurovascularly intact, the patient is given analgesia and discharged home.
You are finishing up your shift when you see the same patient from earlier limping back into the ED. This time he is complaining of right lower extremity weakness and a new tingling sensation throughout his right leg in addition to worsening pain. What could have been considered in the differential diagnosis the first time around?
Given the title, I’m sure you can guess what issue this patient is presenting with…exactly, limb ischemia. And given that we are discussing systemic AAA repair complications, I’m sure you’ve deduced that the root cause of the patient’s limb ischemia is that darn AAA graft. Now, should we have truly considered a graft complication on his very first visit? No. But we definitely could have thought about limb ischemia which thus begs the question, why is the patient experiencing ischemia?
Below we will discuss the systemic complications of EVAR and the management and disposition of these patients from the Emergency Medicine point of view.
Systemic Complications:
Limb Ischemia:
– Incidence: 5% in new generation grafts; up to 40% in older generation grafts[1]
– Timeline: 2 months to 5 years[1]
– Pathophysiology: Graft kinking, embolism from the graft, or migration of the graft resulting in external iliac artery occlusion.[1]
– Presentation: One or more of the classic “6 Ps”: claudication pain (the earliest sign), paraesthesia with associated weakness, pallor, and less commonly the late findings of paralysis, pulselessness, and poikilothermia.
– Risk Stratification: Below are two charts that may be used to risk stratify these patients and guide management.[4] These stages are based on the Rutherford classification of acute limb ischemia and are recommended by the Society for Vascular Surgery and the North American Chapter of the International Society for Cardiovascular Surgery.
Table 1. Categorizing patients into different stages based on clinical findings.[4]
Figure 3. Management of limb ischemia based on staging (see table 1).[4]
Figure 4. Image of graft kinking that can lead to occlusion of the external iliac artery and limb ischemia.[1]
Figure 5. Left stent-graft-limb kinking.(a, b) Coronal CT images and (c) volume rendering reconstruction CT angiography taht show left limb kinking (arrows) with angulation of about 90°.[14]
– Incidence: <5% for renal artery ischemia and < 3% for bowel ischemia[1]
– Timeline: < 30 days post-op[1]
– Pathophysiology: Renal ischemia results either from unintentional coverage of the origin of the renal arteries by the endograft intra-procedurally or from endograft migration post-operatively.[3] Bowel ischemia occurs if endograft migration obstructs the inferior mesenteric artery. The left colon is particularly susceptible as this region has poorly developed mesenteric collateral arcades.[2]
– Presentation: Both of these complications have a subacute presentation with patients complaining of abdominal pain, flank pain, and/or bloody diarrhea.[2,3] Make sure to be on extra high alert for bowel ischemia if patients with a concerning history present with LLQ abdominal pain.[2]
Spinal Cord Ischemia
– Incidence: < 0.2% of abdominal EVAR but up to 12% in thoracic EVAR[1]
– Timeline: ≤ 12 hours post-op[1]
– Pathophysiology: Intraoperative hypotension, disruption or occlusion of the radicular artery (which perfuses large segments of the spinal cord), and prolonged aortic occlusion by the device, limiting blood flow.[13]
– Presentation: Neurological deficits will depend on the spinal level involved. Given that this occurs in the immediate post-op period, these patients will still be on the surgical floor or in PACU and are unlikely to present to the ED with this complication.
Evaluation:
CT: The modality of choice is a triple phase CT (non-contrast, arterial phase, and delayed phase). In a meta-analysis, the sensitivity and specificity of CTA to detect aortoiliac stenosis > 50% were reported as 96% and 98%, respectively.[6]
Doppler US (DUS): This can help with staging (see Table 1 above).[4,8]
Management:
Heparin: Do we heparinize these patients empirically before obtaining results from CT? That is a difficult question. Most of these complications are due to stent graft migration or kinking, which don’t lend themselves to heparin therapy. On the other hand, the stent graft itself is a nidus for thrombus formation, and if the patient has not been compliant with anticoagulation (AC) and/or antiplatelet (AP) therapy, there could be a compounded effect. What is clear, however, is if there are concerning signs of limb ischemia, then yes, you should heparinize prior to CT results. Heparinization remains one of the mainstays in the treatment of acute limb ischemia and is shown to prevent proximal and/or distal thrombus propagation, and preserve microcirculation.[14] If there are no contraindications (Table 2), then consider a heparin bolus of 80 units/kg followed by a heparin drip at 18 units/kg/hr.
Bowel Ischemia: Initial treatment for bowel ischemia includes broad-spectrum antibiotic therapy with coverage of colonic flora to prevent and treat sepsis, e.g. a 2nd generation cephalosporin with metronidazole OR fluoroquinolone with metronidazole OR piperacillin/tazobactam.[9][10] Recommendations on starting heparin vary– some recommend delaying heparin for 48 hours due to the risk of intraluminal bleeding in bowels with catheter-directed thrombolysis being the preferred option.[9,10] Consider discussing with your institution’s vascular surgery team prior to initiating heparin therapy for bowel ischemia.
Renal Ischemia: The optimal treatment for renal ischemia remains uncertain given the absence of comparative studies. There have been many reported approaches including anticoagulation, percutaneous endovascular therapy (thrombolysis, thrombectomy with or without angioplasty, or stent placement), and open surgery. Therefore, consult your surgeons before proceeding with interventions.[11,12]
Table 2. Contraindications for unfractionated heparin use.
At the end of the day, these patients will require vascular surgery consultation for either endovascular revascularization (stent placement, percutaneous aspiration thrombectomy, percutaneous mechanical thrombectomy, or catheter-directed pharmacological recanalization via thrombolytic agents) or open revascularization (thrombectomy with a balloon catheter, bypass surgery with use of adjuncts such as endarterectomy, patch angioplasty, and intraoperative thrombolysis).[4,8,9,10,11,12]
Regardless of the form of ischemia, the diagnosis of systemic complications of EVAR relies on clinical suspicion.
Our vascular surgery colleagues will want to know the following:
Are they on anticoagulation/antiplatelet therapy and if so which one and when was the last dose?
Has the patient had their yearly surveillance imaging and if so when was the last one and what did it show?
How was the AAA repaired (endovascular or open surgery), when was it repaired, and what type of graft was used? I included a list of FDA-approved EVAR grafts below.[11]
Table 3. FDA-Approved Devices for EVAR.[5]
Summary/Key Points:
EVAR systemic complications include limb ischemia (most common), bowel ischemia, renal ischemia, and spinal ischemia.
The most common systemic graft complication is limb ischemia.
In patients with limb ischemia secondary to graft complications who do not have contraindications to anticoagulation, initiate a bolus of unfractionated heparin 80 units/kg followed by a heparin drip at 12 units/kg/hr.
In patients with bowel ischemia secondary to graft complications it is important to start antibiotics to prevent sepsis
See related posts!!! http://blog.clinicalmonster.com/2020/04/14/acute-vs-chronic-abdominal-aortic-dissection/, http://blog.clinicalmonster.com/2017/03/14/em-critical-care-aortic-dissection/, http://blog.clinicalmonster.com/2017/03/07/clinical-ct-april-2016/
References
1. Daye D, Walker T. Complications of endovascular aneurysm repair of the thoracic and abdominal aorta: evaluation and management. Cardiovasc Diagn Ther. 2018;8(S1):S138-S156. doi:10.21037/cdt.2017.09.17
2. Becquemin JP, Majewski M, Fermani N, et al. Colon ischemia following abdominal aortic aneurysm repair in the era of endovascular abdominal aortic repair. J Vasc Surg 2008;47:258-63; discussion 263. 10.1016/j.jvs.2007.10.001
3. Chang, C., Chuter, T., Niemann, C., Shlipak, M., Cohen, M., Reilly, L. and Hiramoto, J., 2009. Systemic inflammation, coagulopathy, and acute renal insufficiency following endovascular thoracoabdominal aortic aneurysm repair. Journal of Vascular Surgery, 49(5), pp.1140-1146.
4. Creager, M., Kaufman, J. and Conte, M., 2012. Acute Limb Ischemia. New England Journal of Medicine, 366(23), pp.2198-2206.
5. Jackson, B. and Carpenter, J., 2009. Devices Used for Endovascular Aneurysm Repair: Past, Present, and Future. Seminars in Interventional Radiology, 26(01), pp.039-043.
6. Met, R., Bipat, S., Legemate, D., Reekers, J. and Koelemay, M., 2009. Diagnostic Performance of Computed Tomography Angiography in Peripheral Arterial Disease. JAMA, 301(4), p.415.
7. Ivancev, K. and Vogelzang, R., 2020. A 35 Year History of Stent Grafting, and How EVAR Conquered the World. European Journal of Vascular and Endovascular Surgery, 59(5), pp.685-694.
8. Olinic, D., Stanek, A., Tătaru, D., Homorodean, C. and Olinic, M., 2019. Acute Limb Ischemia: An Update on Diagnosis and Management. Journal of Clinical Medicine, 8(8), p.1215.
9. Klar E, Rahmanian P, Bücker A, Hauenstein K, Jauch K, Luther B. Acute Mesenteric Ischemia. Deutsches Ärzteblatt international. 2012. doi:10.3238/arztebl.2012.0249
10. American Gastroenterological Association medical position statement: Guidelines on intestinal ischemia. Gastroenterology. 2000;118(5):951-953. doi:10.1016/s0016-5085(00)70182-x
11. Ouriel K, Andrus C, Ricotta J, DeWeese J, Green R. Acute renal artery occlusion: When is revascularization justified?. J Vasc Surg. 1987;5(2):348-355. doi:10.1067/mva.1987.avs0050348
12. Bouttier S, Valverde J, Lacombe M, Nussaume O, Andreassian B. Renal Artery Emboli: The Role of Surgical Treatment. Ann Vasc Surg. 1988;2(2):161-168. doi:10.1016/s0890-5096(06)60800-5
13. Szilagyi DE. A second look at the etiology of spinal cord damage in surgery of the abdominal aorta. J Vasc Surg. 1993;17(6):1111-1113.
14. Gozzo C, Caruana G, Cannella R et al. CT angiography for the assessment of EVAR complications: a pictorial review. Insights Imaging. 2022;13(1). doi:10.1186/s13244-021-01112-4
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