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Endovascular Management of Visceral Arterial Aneurysms
Endovascular Management of Visceral Arterial Aneurysms Jeanette H. Hemp, MD, and Saher S. Sabri, MD Visceral artery aneurysms are rare entities involving the celiac, superior mesenteric or inferior mesenteric arteries and their branches. While the natural history of these aneurysms is not well known as many are found incidentally, a definite risk of rupture and subsequent mortality has been demonstrated. There are several endovascular methods that an operator may choose to treat visceral artery aneurysms, and selection of the appropriate technique depends on the type and size of aneurysm and the anatomy of the affected artery. It is the aim of this paper to describe the indications, technical considerations and endovascular methods of treatment of visceral artery aneurysms and pseudoaneurysms. The following techniques of angiographic intervention are presented and discussed: isolation, covered stents, coil packing, liquid embolic agents and percutaneous thrombin injection. Where appropriate, individual aneurysm and artery specific treatment considerations are emphasized. To guide and assist practice, a suggested treatment algorithm is presented. Tech Vasc Interventional Rad 18:14-23 C 2015 Elsevier Inc. All rights reserved. KEYWORDS Aneurysm, Pseudoaneurysm, Visceral, Embolization
Introduction Visceral artery aneurysms (VAAs) are rare entities involving the celiac, superior mesenteric, or inferior mesenteric arteries and their branches, with a prevalence of 0.1%2%.1 A true aneurysm affects all 3 vessel walls, with multiple etiologies ranging from collagen vascular diseases to vasculitides (Table 1).2-6 The splenic artery is most commonly affected, followed by the hepatic artery; however, any visceral artery may be involved. Although the natural history of these aneurysms is not well known, as many are found incidentally on studies performed for other reasons, a definite risk of rupture has been demonstrated.1,6-9 Depending on size and location, mortality from rupture ranges from 25%-100%.1,2 Treatment recommendations are based on the specific artery affected. Visceral artery pseudoaneurysms (VAPAs), or false aneurysms, only involve the outermost vessel wall and are secondary to infectious, inflammatory, or iatrogenic causes and have an increased propensity to progress to rupture as compared with true aneurysms. Commonly, they are found in the setting of pancreatitis or postbiliary Department of Radiology, University of Virginia Health System, Charlottesville, VA. Address reprint requests to Saher S. Sabri, MD, Department of Radiology, University of Virginia Health System, Box 800170, 1215 Lee St, Charlottesville, VA 22908-0170. E-mail: [email protected]
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intervention. In contrast to true aneurysms, pseudoaneurysms are often symptomatic, with a study reporting 92% requiring urgent intervention because of hemorrhage.1 Because of the increased risk of rupture, it is recommended that all pseudoaneurysms be repaired. There are several endovascular methods that an operator may choose, and the selection of the appropriate technique depends on the type and size of the aneurysm and the anatomy of the affected artery. Techniques include isolation, covered stents, coil packing, liquid embolic agents, and percutaneous thrombin injection. It is the aim of this article to describe the indications, technical considerations, and endovascular methods of treatment of VAAs and VAPAs.
Indications and Artery-Specific Considerations As there have been no prospective studies, indications to treat VAAs and VAPAs are variable, with differing recommendations found in the literature. Universally, it is agreed that pseudoaneurysms of any size should be treated. There are few large studies that evaluate aneurysms by their parent artery; however, from those that do exist, a loose consensus has been reached (Table 2).2,4,5,10-12 Particularly, repair is recommended for all VAAs that demonstrate interval growth or are symptomatic. Pseudoaneurysms are
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Endovascular management of visceral aneurysms Table 1 Pathogenesis of VAA and VAPA True aneurysms Atherosclerosis (32%) Medial degeneration or dysplasia (24%) Abdominal trauma (22%) Infection or inflammation (10%) Hypertension Connective tissue disorders Marfan syndrome, Ehlers-Danolos syndrome, OslerWeber-Rendu disease, systemic lupus erythematosus, Behçet syndrome, fibromuscular dysplasia, and alpha1-antitrypsin deficiency Hyperflow Portal hypertension, pregnancy, and median arcuate ligament syndrome Vasculitis Polyarteritis nodosa, Takayasu arteritis, Kawasaki disease, and Wegener granulomatosis Neurofibromatosis Hereditary hemorrhagic telangiectasia Long-term amphetamine use Pseudoaneurysms Iatrogenic Surgery, endoscopy, and interventional procedures Trauma Infection or inflammation
often found in the setting of multiple comorbidities, and these patients are particularly likely to benefit from an endovascular approach.
Celiac Artery Celiac artery aneurysms are the fourth most common VAAs, accounting for 4% of all VAAs.12,13 Association with other aneurysms is very common, with a study reporting a rate of 66%.14 The risk of rupture has been demonstrated at 10%-20%, with 72% being asymptomatic at presentation.14 Mortality at rupture has been reported as high as 100%.1 These aneurysms are most likely due to atherosclerosis; however, the celiac trunk itself can be affected by median arcuate ligament syndrome with poststenotic dilatation owing to altered flow mechanics with retrograde Table 2 General Guidelines for Intervention True aneurysms Symptomatic Women of childbearing age Patients who may require a liver transplant Nonatherosclerotic etiology (ie, connective tissue disease) Interval growth 40.5 cm/y Multiple hepatic VAA 42 cm Hepatic, splenic, or celiac VAAs Any size rare VAA (SMA and branches and IMA aneurysms) Pseudoaneurysms All
15 flow through the pancreatic arcades.13 Symptoms can include abdominal pain and mimic pancreatitis.14 Endovascular repair is most suitable in patients who are at high surgical risk with good, nondiseased collateral circulation, although studies of aortic aneurysm repair have shown that the proximal celiac artery may be embolized safely.12,14,15
Splenic Artery Splenic artery aneurysms are the most common true aneurysms, comprising 50%-75% of all VAAs. They are found in conjunction with other splanchnic aneurysms in 3% of cases and with other nonvisceral aneurysms in 14%.3 Most are saccular and located in the middle-todistal splenic artery.10 The rate of rupture is low and has been estimated at 3%-20%.2,3,16 True aneurysms have been found more commonly in women and in association with multiparty and portal hypertension, whereas pseudoaneurysms are more commonly seen in the setting of pancreatitis.3,10 Endovascular repair of splenic artery aneurysms must take into account the tortuosity of the parent artery. For example, stent graft placement is difficult in a distal tortuous vessel; however, it may be appropriate for proximal splenic aneurysms. With a rich collateral flow between the celiac axis and the superior mesenteric artery (SMA) via the pancreaticoduodenal arteries, as well as collateral flow to the spleen via the short gastric arteries, embolization can be undertaken with less risk for ischemia. As such, splenic artery aneurysms are good candidates for coil embolization.
Hepatic Artery Hepatic artery aneurysms are the second most common true aneurysms comprising 20% of all visceral aneurysms.4 They are found in conjunction with other VAAs in 31% of cases and nonvisceral aneurysms in 42%; however, they are most often solitary. In contrast to splenic artery aneurysms, true aneurysms have been found to be more common in men. An increased risk of rupture was found in cases of multiple aneurysms or with aneurysms of nonatherosclerotic etiology, such as those with fibromuscular dysplasia or polyarteritis nodosa.4 Rupture rates as high as 80% have been described, with a mortality rate of 20%.2 Hepatic artery aneurysms may rupture into the biliary tree, resulting in Quincke’s triad of jaundice, biliary colic, and gastrointestinal hemorrhage. Overall, extrahepatic aneurysms are more common. In particular, the incidence of hepatic pseudoaneurysms is rising because of the increasing use of hepatic interventions such as percutaneous transhepatic cholangiography and transarterial chemoembolization. Endovascular repair of intrahepatic aneurysms is considered first line because of the complicated nature of open repair. However, special attention must be given to limit end-organ ischemia when aneurysms of the proper hepatic artery are addressed, as there is not appropriate collateral flow to compensate in the event of complete occlusion.
16 In this setting, the use of stent graft repair is preferred to ensure distal perfusion.
Superior Mesenteric Artery SMA aneurysms are the third most common true visceral aneurysm and most commonly affect the proximal 5 cm of the artery. These aneurysms have been found to be more common in men with a presenting rupture rate of 38%.5,12 Especially in the SMA territory, elective intervention may prevent visceral ischemia. Indications for repair vary, with some studies recommending that all SMA aneurysms should be repaired because of the limited natural history data available.5,14 SMA aneurysms that are most appropriate for embolization are those that are distal to the origin of the SMA, with small necks and good collateral flow.5
SMA Branches True gastroduodenal and pancreaticoduodenal aneurysms are rare, with unpredictable behavior. Gastroduodenal artery (GDA) aneurysms are more often VAPAs, secondary to pancreatitis.17 Symptoms may include abdominal pain and a pulsating mass.18 Rupture rates of GDA aneurysms range between 20% and 80%, prompting some authors to recommend that all should be repaired, regardless of size. Aneurysms in these territories can result from median arcuate ligament compression with altered flow mechanics and increased intravascular pressure from retrograde flow through the pancreatic arcades. As in the SMA, adequate collateral flow should be demonstrated before intervention. In a large retrospective study of GDA aneurysms, 52% of patients presented with gastrointestinal hemorrhage, with 40% of those ruptures leading to death. Only 7.5% were asymptomatic.19
Inferior Mesenteric Artery Inferior mesenteric artery (IMA) aneurysms are extremely rare, with few reports in the literature.20 IMA aneurysms most commonly occur in the proximal IMA trunk. IMA aneurysms are more common in men, and most are due to atherosclerosis. Of the known cases, 21 are associated with occlusion of the celiac and the SMA.20,21 Symptoms may include abdominal pain and an enlarging mass, although approximately half of cases are asymptomatic. Because of the rarity of the condition, rupture rates are not known; however, rupture has been demonstrated.20
Workup or Contraindications Multiple imaging modalities may reveal the presence of a VAA or VAPA. Angiography, plain radiographs, ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) have been used to arrive at the diagnosis.5,14 Diagnostic workup for both elective and urgent interventions are similar and include imaging characterization of the aneurysm. Some authors advocate for duplex US and computed tomography angiography in
J.H. Hemp and S.S.Sabri elective cases and for computed tomography angiography in hemodynamically stable but urgent cases, to evaluate the visceral collateral arterial circulation.22 Clinical workup includes a detailed history, focused physical examination, and recent blood analysis including complete blood (cell) count, international normalized ratio, creatine, glomerular filteration rate, platelets, partial thromboplastin time, and C-reactive protein.13 Consent must be obtained. Ideally, the patient is recommended to have nothing by mouth for 6 hours. Intravenous access is necessary for fluid resuscitation and conscious sedation.13 Absolute contraindications to endovascular intervention include hemodynamic instability that cannot be corrected or life-threatening anaphylaxis to contrast. It is worth noting that an acute rupture, especially in the retroperitoneum, may stabilize because of tamponade from surrounding hematoma and does not preclude endovascular treatment.23
Endovascular Management Methods General Technical Considerations Interventions for visceral aneurysms are usually performed from a common femoral arterial access. Brachial or radial arterial access can be considered when the targeted mesenteric vessel takes off the aorta at a steep angle. This access can also be helpful when median arcuate compression of the SMA or the celiac is present. Selective catheterization can be performed using a variety of selective angiographic catheters. The fluoroscopic frame rate during digital subtraction angiography can be adjusted to be 4-6 frames per second to allow visualization of the arterial branches feeding the aneurysm. The need to place a sheath in the mesenteric artery depends on the type of intervention performed and the stability of the catheter system in the mesenteric vasculature. If a sheath is required, a long sheath (eg, Ansel, Raabe Flexor sheaths, Cook Inc., Bloomington, IN) is recommended to be placed in the aorta before selective catheterization of the mesenteric artery. A stiff wire (Rosen or Amplatz, Cook Inc., Bloomington, IN) can be placed through the 5-F catheter, and the sheath can be advanced over the stiff wire into the mesenteric artery origin using the 5-F catheter as a “dilator,” or by exchanging the 5-F catheter for the sheath dilator before advancing into the ostium. To aid in advancing the stiff wire into the mesenteric branch to be treated (eg, the splenic artery), the selective 5-F catheter can be advanced into the middle or distal splenic artery over a hydrophilic wire (Glidewire, Terumo). The stiff wire is then advanced through the 5-F catheter. If the 5-F selective catheter could be advanced deep into the splenic artery, it can be exchanged for a 4-F hydrophilic catheter (Slip-Cath, Cook Inc, or Glidecath, Terumo), which can be advanced into the distal artery over a hydrophilic wire. Simmons 2 and 3 catheters (Angiodynamics) can also be helpful in gaining “purchase” into the distal artery before the stiff wire is placed. A detailed description of different
Endovascular management of visceral aneurysms
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Figrue 1 The suggested algorithm for treating visceral aneurysms and pseudoaneurysms. (Color version of figure is available online.)
endovascular techniques used to treat VAAs and VAPAs is given later. The choice of the technique relies on the need to preserve the parent artery, the morphology of the aneurysm, and the tortuosity of the parent artery (Fig. 1).
Isolation Isolation includes embolization of the aneurysmal artery, first distal and then proximal to the location of the aneurysm, the so-called sandwich technique. Careful evaluation of the angiographic images is critical to determine all inflow and outflow arteries of the aneurysm. Successful isolation of the aneurysm is dependent on successful embolization of all inflow and outflow arteries. Depending on the vessel size and tortuosity, a 0.035-in system or microembolization system can be chosen. A 0.035-in system is used for larger arteries (43 mm) with a more proximally located aneurysm with single inflow and outflow. This can be achieved by using metallic coils or vascular plugs (VPs). 0.035-in Metallic Coils The selective angiographic catheter of 4 or 5 F is used to select the mesenteric artery and is then advanced over a hydrophilic wire (Glidewire, Terumo, Somerset, NJ) distal to the aneurysm. If this cannot be achieved, then the selective catheter can be exchanged for a hydrophilic catheter (Slip-Cath, Cook Inc., Bloomington, IN, or Glidecath, Terumo, Somerset, NJ), which can be placed distal to the aneurysm. A sheath can be placed in the origin
of the mesenteric artery to aid in the stability of the catheter during embolization. The coils are sized with 10%-20% oversizing compared with the size of the target artery. A variety of pushable metallic coils (Tornado and Nester, Cook Inc., Bloomington, IN, and Vortex, Boston Scientific, Marlborough, MA) can be used. Detachable coils (eg, Interlock, Boston Scientific, Marlborough, MA) can be used especially in more tortuous arteries, where the operator thinks the catheter may not be stable in position. Pushable Hydrogel coils (Terumo, Somerset, NJ) have also been used and have the advantage of being more thrombogenic because of the presence of the hydrogel that may achieve embolization with fewer coils. Vascular Plugs VPs (AMPLATZER Vascular Plug [AVP], AGA Medical, Plymouth, MN) have been used as an alternative embolization method. Advantages of the VP include easy delivery, a detachable system, and the ability to occlude the artery with a single device. Disadvantages include the need for a larger delivery system compared with using metallic coils. The size of the VP ranges from 4-22 mm. Depending on the size of the VP used, a sheath of 5-7 F is required. The success of this procedure relies on the ability to place the sheath distal to the aneurysm. The technical aspects of advancing the sheath are described earlier. The VP is oversized 20%-40% compared with the target artery. We placed 1 or 2 VPs distal to the aneurysm. Once angiography confirms occlusion of the distal artery, the sheath is retracted across the aneurysm and 1 or 2 VPs are deployed
J.H. Hemp and S.S.Sabri
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Figure 2 Isolation technique. (A) Selective splenic angiogram shows a large splenic aneurysm (arrow). A sheath (arrowheads) is placed in the celiac axis for stability. (B) A microcatheter was placed in one of the outflow vessels (arrow). The sheath was advanced into the origin of the splenic artery (arrowheads). (C) Coil embolization of the outflow arteries was performed with microcoils (arrows). (D) After coiling the splenic artery proximal to the aneurysm, there is stagnation of contrast agent in the aneurysm (arrow), indicating successful isolation.
proximal to the aneurysm. Metallic coils can be used in addition to the VP if there is flow into the aneurysm. A new VP (AVP 4, AGA, Plymouth, MN) is now available that can be placed through a catheter of 4-5 F. The size for AVP 4 ranges from 4-8 mm. This VP can be used alone or in combination with metallic coils. Microcoils Similar to the 0.035-in metallic coils, the microcoils need to be placed in the arterial segment(s) distal and then proximal to the aneurysm. This can be achieved by advancing a microcatheter through the selective catheter of 4-5 F placed in the proximal mesenteric artery. The microcatheter is advanced with the aid of a microwire (0.014-0.25 in) in the arterial segment distal to the aneurysm. A long sheath rarely needs to be placed at the
ostium of the mesenteric artery. One of the advantages of microcoils is the availability of varying sizes of coils ranging from 2-25 mm, both in pushable and detachable forms. Using a microcatheter system allows for treatment of a wide range of aneurysm sizes, and its low profile allows for navigating tortuous arterial anatomy, which can be challenging using a 0.035-in system or VPs (Fig. 2).
Covered Stents To preserve the arterial segment where the aneurysm is present, a covered stent can be placed across the aneurysm (Fig. 3). A long sheath is required to deliver the stent in the mesenteric artery. The sheath is advanced into the ostium of the mesenteric artery or further into the target artery to achieve further stability and allow for tracking of the stent
Endovascular management of visceral aneurysms
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Figure 3 Covered stent and coils to treat a splenic aneurysm. (A) Splenic angiogram shows a distal splenic aneurysm (arrows). It can be noted that a sheath is placed in the splenic artery (arrowheads). (B) The smaller of the 2 outflows was embolized using 0.035-in coils (arrow). The larger outflow artery remains patent (arrowheads). (C) A covered stent (black arrow) was placed across the aneurysm into the larger outflow artery (white arrow).
across the aneurysm. It is recommended to extend the stent at least 10 mm proximal and distal to the aneurysm. Selfexpanding covered stents are recommended to be placed in tortuous arteries (Fig. 4), whereas balloon-expandable covered stents (iCast, Atrium/MAQUET Cardiovascular, Wayne, NJ) can be placed in straight proximal segments of mesenteric arteries. Self-expanding stents such as VIABAHN (W.L. Gore, Flagstaff, AZ) range in size from 5-13 mm and require a sheath of 6-12 F, depending on size. A lower profile VIABAHN stent is now available, deliverable over a 0.018-in wire. This allows for better tracking and need for a lower size sheath. Other self-expanding covered stents include Fluency (Bard, Murray Hill, NJ), which is deployable through a 9-F sheath and has a size range of 8-12 mm.
Coil Packing Coil packing of the aneurysm is used to treat saccular true aneurysms with narrow necks. This technique should not be
used for pseudoaneurysms, as the aneurysm sac continues to expand after coil packing because of the absence of a true vessel wall. Tight packing of the coil mass is critical to achieve technical success for this procedure. Embolization is usually preformed through a microcatheter that is placed in the aneurysm sac. Detachable coils are recommended in this setting, as they provide the most controlled and accurate deployment. 3-dimensional detachable framing coils are usually placed first, and they are sized to match the largest diameter of the aneurysm. Then, smaller framing coils are placed followed by helical-shaped coils of progressively smaller size till tight coil packing is achieved. The entire aneurysm needs to be coiled to prevent recanalization (Fig. 5). Fluoroscopic techniques such as road map and other digital subtraction techniques are useful in visualizing the coils as they are deployed and aid in achieving accurate deployment. Attention needs to be given to avoid herniation of coil material into the parent artery. Detachable coils allow for retraction and repositioning in this setting. If the neck of
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J.H. Hemp and S.S.Sabri
Figure 4 Covered stent to treat a pseudoaneurysm secondary to pancreatitis. (A) Splenic angiogram shows a pseudoaneurysm (arrow) with a jet of contrast agent noted arising from the midsplenic artery. (B) Exclusion of the pseudoaneurysm after placement of a covered stent (arrow).
Figure 5 Coil packing technique. (A) Superior mesenteric angiogram shows an inferior pancreaticoduodenal artery aneurysm (black arrows) in a patient with median arcuate compression of the celiac artery. It can be noted that the outflow of the aneurysm is through the posterior inferior pancreaticoduodenal artery (white arrow). The anterior inferior pancreaticoduodenal artery (white arrowheads) is the main collateral pathway to reconstitute the celiac artery. (B) A sheath (white arrowheads) is placed in the origin of the SMA. A microcatheter (white arrow) is advanced into the outflow artery. A “buddy” 0.014-in wire was placed in the SMA to provide support. (C) Superiomesenteric angiogram shows successful coil packing (black arrow) of the aneurysm and continued filling of the celiac artery (white arrow) through pancreaticoduodenal collaterals.
Endovascular management of visceral aneurysms
Figure 6 Stent-assisted coiling technique. Early (A) and late (B) phases of aortogram and selective angiogram of the aneurysm (C) show a replaced right hepatic artery aneurysm (black arrow). The 2 outflow arteries are replaced right hepatic artery (black arrowheads) and an inferior pancreaticoduodenal artery that reconstitutes the celiac artery (white arrow). (D) A sheath and a diagnostic catheter were advanced through the gastroduodenal artery (black arrow) into the pancreaticoduodenal artery to aid in coiling the aneurysm and the outflow arteries. (E) Replaced right hepatic arteriogram shows a bare metal stent in place (large black arrow) with successful coil packing of the aneurysm (large white arrow). The pancreaticoduodenal artery branches were embolized with microcoils (small black arrows) and a vascular plug (white arrow).
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J.H. Hemp and S.S.Sabri
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Figure 7 Liquid embolic agents in tortuous arteries. (A) Splenic angiogram shows an extremely tortuous splenic artery with multiple aneurysms of varying sizes (black arrows). (B) The aneurysms were excluded using a combination of coils and onyx (black arrows).
the aneurysm is too wide, stent-assisted coiling can be performed. For this technique, a bare metal stent is placed across the saccular aneurysm in the parent artery (Fig. 6). Through the interstices of the stent, a microcatheter can be placed into the sac, and coil packing can be performed without the risk of herniation into the parent artery. Alternatively, the microcatheter can be placed in the aneurysm sac before stent deployment. The stent is then deployed alongside the microcatheter over a “buddy” wire. The advantage of this technique is that it guarantees access into the aneurysm sac. The disadvantage is the need for a larger sheath to accommodate a microcatheter alongside the bare metal stent.
Liquid Embolic Agents Liquid embolic agents such as n-butyl cyanoacrylate glue and onyx can be used to embolize the inflow and outflow arteries or filling the aneurysm sac itself. A useful application is in extremely tortuous arteries, where pushability of coils is limited (Fig. 7). Liquid agents can be injected through the microcatheter first in the distal artery(ies) until complete filling of the target artery(ies) is noted. The catheter can be retracted to the artery proximal to the aneurysm, which can be embolized using liquid agents or coils. Alternatively, the aneurysm sac can be filled with liquid agents, if preservation of the parent artery is planned. However, spillage of liquid agents into the parent artery is a risk, and careful incremental injection of liquid agents is recommended. A balloon-assisted technique can be used. A balloon is placed in the parent artery across the aneurysm sac alongside a microcatheter placed in the aneurysm sac. Liquid agents can be injected directly into the sac. The balloon prevents spillage of liquid agent. However, overfilling should be avoided, as spillage can still occur after balloon deflation.
Percutaneous Thrombin Injection Thrombin can be injected directly into the sac to aid in thrombosis. This technique is particularly useful in mesenteric artery pseudoaneurysms and especially if the aneurysm neck is narrow and long. The concept is similar to thrombin injection to treat femoral pseudoaneurysms after arterial puncture. Access into the sac can be transarterial by placing a microcatheter into the aneurysm sac and injecting incremental amounts of thrombin until stasis is confirmed by transabdominal US or by performing angiogram from the parent artery. Alternatively, access into the sac can be achieved percutaneously using CT, US, or fluoroscopy guidance. If the neck is wide or short, balloon-assisted thrombin injection can be performed with a balloon inflated across the aneurysm neck in the parent artery during thrombin injection. The major disadvantage of thrombin is that it is not radiopaque and distal embolization may not be recognized during the procedure.
Outcomes, Complications, and Follow-up Historically, open resection or ligation of visceral aneurysms has been the gold standard for treatment of VAAs and VAPAs; however, endovascular methods have been increasingly used with excellent results and offer an effective alternative therapy for poor surgical candidates. Although most reports in the literature are smaller series, the largest studies have demonstrated technical success rates ranging from 89%-98%.1,6,24 Studies have also demonstrated that there is no significant difference in the morbidity and mortality rates between open and endovascular methods and that the reintervention rate between surgery and endovascular treatments is not different.
Endovascular management of visceral aneurysms Studies have also demonstrated decreased hospital stay, when compared with surgical repair, with a mean hospital stay of 3.8 vs 12 days. A significant difference in survival between aneurysms treated electively vs urgently underscores the need for early, elective intervention.7,24 Observed complications have been minor in general. As with any procedure that requires arterial access, there is a risk of access-related complications such as groin hematoma, retroperitoneal hematoma, femoral artery pseudoaneurysm, femoral artery thrombosis, or embolism. The possibility of contrast agent–induced nephropathy must be considered in those with poor renal function; however, CO2 can be used in some situations as an alternative contrast agent.1 Specific to treatment of splenic artery aneurysms, splenic infarcts and postembolization syndrome has been observed in up to 40% of patients and are more often associated with distal splenic artery aneurysms. In general, the condition is often self-limited and managed with pain medications.3,6,24 Specific to the treatment of hepatic artery aneurysms, there is a risk of hepatic ischemia, hepatic abscess, and cholecystitis.4 Treatment failures including persistent perfusion, recanalization, and coil migration have been observed, with reperfusion rates of 10.3% in the first month.1,4,16 Failures may be related to technical difficulties in catheterizing the aneurysm neck, resulting in intraprocedural dissection or rupture, and may be more frequently encountered with treatment of large aneurysms, as large neck size and turbulence can lead to unstable coils and incomplete sac packing.7,18 In the setting of the isolation technique for saccular aneurysms, there is a risk of coil migration into the pseudoaneurysm with associated growth in sac size. While using stents, there is a risk of stent migration or stent occlusion requiring reintervention.7 Pseudoaneurysms are particularly prone to recurrent bleeding due to pancreatitis or other persistent inflammatory states.6 The potential for early and late failure such as growth in sac size or leak, which would require reintervention, necessitates early and serial imaging follow-up.11 Unfortunately, the same radiopaque materials that allow fluoroscopic visualization and endovascular treatment often preclude sensitive CT evaluation because of artifact.1 Some authors advocate for the use of contrast-enhanced US or MRI to verify complete aneurysmal sac occlusion.16 Proposed imaging protocols include followup imaging in 1 week to 30 days; CT follow-up at 1, 6, and 12 months; and yearly CT or MRI.7,9,12,16 In summary, endovascular treatment of aneurysms and pseudoaneurysms is technically feasible with excellent outcomes, lower morbidity, and shorter hospital stay than open procedures are. Interventional radiologists should be familiar with the diagnosis, general indications, and specific techniques of endovascular treatment of visceral artery aneurysms and pseudoaneurysms as discussed earlier. Additionally, interventionalists should also be aware that anatomical variation necessitates an artery-specific treatment approach. The choice of technique relies on the need to preserve the parent artery, the morphology of the aneurysm, and the tortuosity of the parent artery, as presented in the suggested treatment algorithm. Techniques discussed
23 include isolation, covered stent, coil packing, liquid embolic agents, and percutaneous thrombin injection.
References 1. Tulsyan N, Kashyap VS, Greenberg RK, et al: The endovascular management of visceral artery aneurysms and pseudoaneurysms. J Vasc Surg 45:276-283, 2007 2. Cordova AC, Sumpio BE: Visceral artery aneurysms and pseudoaneurysms—Should they all be manage by endovascular techniques? Ann Vasc Dis 6:687-693, 2013 3. Abbas MA, Stone WM, Fowl RJ, et al: Splenic artery aneurysms: Two decades of experience at Mayo clinic. Ann Vasc Surg 16:442-449, 2002 4. Abbas MA, Fowl RJ, Stone WM, et al: Hepatic artery aneurysm: Factors that predict complications. J Vasc Surg 38:41-45, 2003 5. Stone WM, Abbas M, Cherry KJ, et al: Superior mesenteric artery aneurysms: Is presence an indication for intervention? J Vasc Surg 36:234-237, 2002 6. Gabelmann A, Gorich J, Merkle E: Endovascular treatment of visceral artery aneurysms. J Endovasc Ther 9:38-47, 2002 7. Ferrero E, Ferro M, Viazzo A, et al: Visceral artery aneurysms, an experience on 32 cases in a single center: Treatment from surgery to multilayer stent. Ann Vasc Surg 25:923-935, 2011 8. Kasirajan K, Greenberg RK, Clair D, et al: Endovascular management of visceral artery aneurysm. J Endovasc Ther 8:150-155, 2001 9. Fankhauser GT, Stone WM, Naidu SG, et al: The minimally invasive management of visceral artery aneurysms and pseudoaneurysms. J Vasc Surg 53:966-970, 2011 10. Nosher JL, Chung J, Brevetti LS, et al: Visceral and renal artery aneurysms: A pictorial essay on endovascular therapy. Radiographics 26:1687-1704, 2006 11. Berceli SA: Hepatic and splenic artery aneurysms. Semin Vasc Surg 18:196-201, 2005 12. Sachdev-Ost U: Visceral artery aneurysms: Review of current management options. Mt Sinai J Med 77:296-303, 2010 13. Kos S, Liu DM, Jacob AI: Mesenteric aneurysms. in Geshwind JH, Dake MD (eds.), Abrams’ Angiography. Philadelphia, PA: Lippincott Williams & Wilkins, 712-722, 2006 14. Stone WM, Abbas MA, Gloviczki P, et al: Celiac arterial aneurysms. Arch Surg 137:670-674, 2002 15. Waldenberger P, Bendix N, Peterson J, et al: Clinical outcome of endovascular therapeutic occlusion of the celiac artery. J Vasc Surg 46:655-661, 2007 16. Lagana D, Carrafiello G, Mangini M, et al: Multimodal approach to endovascular treatment of visceral artery aneurysms and pseudoaneurysms. Eur J Radiol 59:104-111, 2006 17. Kueper MA, Ludescher B, Koenigsrainer I, et al: Successful coil embolization of a ruptured gastroduodenal artery aneurysm. Vasc Endovasc Surg 41:568-571, 2008 18. Marone EM, Mascia D, Kahlberg A, et al: Is open repair still the gold standard in visceral artery aneurysm management? Ann Vasc Surg 25:936-946, 2011 19. Habib N, Hassan S, Abdou R, et al: Gastroduodenal artery aneurysm, diagnosis, clinical presentation and management: A concise review. Ann Surg Innov Res 7:4, 2013 20. Edogawa S, Shibuya T, Kurose K, et al: Inferior mesenteric artery aneurysm: Case report and literature review. Ann Vasc Dis 6:98-101, 2013 21. Tsukioka K, Nobara H, Nishimura K: A case of inferior mesenteric artery aneurysm with an occlusive disease in superior mesenteric artery and the celiac artery. Ann Vasc Dis 3:160-163, 2010 22. Ferrero E, Viazzo A, Ferri M, et al: Management and urgent repair of ruptured visceral artery aneurysms. Ann Vasc Surg 25:e7-e11, 2011 23. Jackson JE: Management of visceral aneurysms. in Mauro MA (ed.), Image-Guided Interventions. Philadelphia, PA: Saunders, 851-862, 2014 24. Sachdev U, Baril DT, Ellozy SH, et al: Management of aneurysms involving the branches of the celiac and superior mesenteric arteries: A comparison of surgical and endovascular therapy. J Vasc Surg 44:718-723, 2006
Introduction Visceral artery aneurysms (VAAs) are rare entities involving the celiac, superior mesenteric, or inferior mesenteric arteries and their branches, with a prevalence of 0.1%2%.1 A true aneurysm affects all 3 vessel walls, with multiple etiologies ranging from collagen vascular diseases to vasculitides (Table 1).2-6 The splenic artery is most commonly affected, followed by the hepatic artery; however, any visceral artery may be involved. Although the natural history of these aneurysms is not well known, as many are found incidentally on studies performed for other reasons, a definite risk of rupture has been demonstrated.1,6-9 Depending on size and location, mortality from rupture ranges from 25%-100%.1,2 Treatment recommendations are based on the specific artery affected. Visceral artery pseudoaneurysms (VAPAs), or false aneurysms, only involve the outermost vessel wall and are secondary to infectious, inflammatory, or iatrogenic causes and have an increased propensity to progress to rupture as compared with true aneurysms. Commonly, they are found in the setting of pancreatitis or postbiliary Department of Radiology, University of Virginia Health System, Charlottesville, VA. Address reprint requests to Saher S. Sabri, MD, Department of Radiology, University of Virginia Health System, Box 800170, 1215 Lee St, Charlottesville, VA 22908-0170. E-mail: [email protected]
14
intervention. In contrast to true aneurysms, pseudoaneurysms are often symptomatic, with a study reporting 92% requiring urgent intervention because of hemorrhage.1 Because of the increased risk of rupture, it is recommended that all pseudoaneurysms be repaired. There are several endovascular methods that an operator may choose, and the selection of the appropriate technique depends on the type and size of the aneurysm and the anatomy of the affected artery. Techniques include isolation, covered stents, coil packing, liquid embolic agents, and percutaneous thrombin injection. It is the aim of this article to describe the indications, technical considerations, and endovascular methods of treatment of VAAs and VAPAs.
Indications and Artery-Specific Considerations As there have been no prospective studies, indications to treat VAAs and VAPAs are variable, with differing recommendations found in the literature. Universally, it is agreed that pseudoaneurysms of any size should be treated. There are few large studies that evaluate aneurysms by their parent artery; however, from those that do exist, a loose consensus has been reached (Table 2).2,4,5,10-12 Particularly, repair is recommended for all VAAs that demonstrate interval growth or are symptomatic. Pseudoaneurysms are
1089-2516/15/$ - see front matter & 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1053/j.tvir.2014.12.003
Endovascular management of visceral aneurysms Table 1 Pathogenesis of VAA and VAPA True aneurysms Atherosclerosis (32%) Medial degeneration or dysplasia (24%) Abdominal trauma (22%) Infection or inflammation (10%) Hypertension Connective tissue disorders Marfan syndrome, Ehlers-Danolos syndrome, OslerWeber-Rendu disease, systemic lupus erythematosus, Behçet syndrome, fibromuscular dysplasia, and alpha1-antitrypsin deficiency Hyperflow Portal hypertension, pregnancy, and median arcuate ligament syndrome Vasculitis Polyarteritis nodosa, Takayasu arteritis, Kawasaki disease, and Wegener granulomatosis Neurofibromatosis Hereditary hemorrhagic telangiectasia Long-term amphetamine use Pseudoaneurysms Iatrogenic Surgery, endoscopy, and interventional procedures Trauma Infection or inflammation
often found in the setting of multiple comorbidities, and these patients are particularly likely to benefit from an endovascular approach.
Celiac Artery Celiac artery aneurysms are the fourth most common VAAs, accounting for 4% of all VAAs.12,13 Association with other aneurysms is very common, with a study reporting a rate of 66%.14 The risk of rupture has been demonstrated at 10%-20%, with 72% being asymptomatic at presentation.14 Mortality at rupture has been reported as high as 100%.1 These aneurysms are most likely due to atherosclerosis; however, the celiac trunk itself can be affected by median arcuate ligament syndrome with poststenotic dilatation owing to altered flow mechanics with retrograde Table 2 General Guidelines for Intervention True aneurysms Symptomatic Women of childbearing age Patients who may require a liver transplant Nonatherosclerotic etiology (ie, connective tissue disease) Interval growth 40.5 cm/y Multiple hepatic VAA 42 cm Hepatic, splenic, or celiac VAAs Any size rare VAA (SMA and branches and IMA aneurysms) Pseudoaneurysms All
15 flow through the pancreatic arcades.13 Symptoms can include abdominal pain and mimic pancreatitis.14 Endovascular repair is most suitable in patients who are at high surgical risk with good, nondiseased collateral circulation, although studies of aortic aneurysm repair have shown that the proximal celiac artery may be embolized safely.12,14,15
Splenic Artery Splenic artery aneurysms are the most common true aneurysms, comprising 50%-75% of all VAAs. They are found in conjunction with other splanchnic aneurysms in 3% of cases and with other nonvisceral aneurysms in 14%.3 Most are saccular and located in the middle-todistal splenic artery.10 The rate of rupture is low and has been estimated at 3%-20%.2,3,16 True aneurysms have been found more commonly in women and in association with multiparty and portal hypertension, whereas pseudoaneurysms are more commonly seen in the setting of pancreatitis.3,10 Endovascular repair of splenic artery aneurysms must take into account the tortuosity of the parent artery. For example, stent graft placement is difficult in a distal tortuous vessel; however, it may be appropriate for proximal splenic aneurysms. With a rich collateral flow between the celiac axis and the superior mesenteric artery (SMA) via the pancreaticoduodenal arteries, as well as collateral flow to the spleen via the short gastric arteries, embolization can be undertaken with less risk for ischemia. As such, splenic artery aneurysms are good candidates for coil embolization.
Hepatic Artery Hepatic artery aneurysms are the second most common true aneurysms comprising 20% of all visceral aneurysms.4 They are found in conjunction with other VAAs in 31% of cases and nonvisceral aneurysms in 42%; however, they are most often solitary. In contrast to splenic artery aneurysms, true aneurysms have been found to be more common in men. An increased risk of rupture was found in cases of multiple aneurysms or with aneurysms of nonatherosclerotic etiology, such as those with fibromuscular dysplasia or polyarteritis nodosa.4 Rupture rates as high as 80% have been described, with a mortality rate of 20%.2 Hepatic artery aneurysms may rupture into the biliary tree, resulting in Quincke’s triad of jaundice, biliary colic, and gastrointestinal hemorrhage. Overall, extrahepatic aneurysms are more common. In particular, the incidence of hepatic pseudoaneurysms is rising because of the increasing use of hepatic interventions such as percutaneous transhepatic cholangiography and transarterial chemoembolization. Endovascular repair of intrahepatic aneurysms is considered first line because of the complicated nature of open repair. However, special attention must be given to limit end-organ ischemia when aneurysms of the proper hepatic artery are addressed, as there is not appropriate collateral flow to compensate in the event of complete occlusion.
16 In this setting, the use of stent graft repair is preferred to ensure distal perfusion.
Superior Mesenteric Artery SMA aneurysms are the third most common true visceral aneurysm and most commonly affect the proximal 5 cm of the artery. These aneurysms have been found to be more common in men with a presenting rupture rate of 38%.5,12 Especially in the SMA territory, elective intervention may prevent visceral ischemia. Indications for repair vary, with some studies recommending that all SMA aneurysms should be repaired because of the limited natural history data available.5,14 SMA aneurysms that are most appropriate for embolization are those that are distal to the origin of the SMA, with small necks and good collateral flow.5
SMA Branches True gastroduodenal and pancreaticoduodenal aneurysms are rare, with unpredictable behavior. Gastroduodenal artery (GDA) aneurysms are more often VAPAs, secondary to pancreatitis.17 Symptoms may include abdominal pain and a pulsating mass.18 Rupture rates of GDA aneurysms range between 20% and 80%, prompting some authors to recommend that all should be repaired, regardless of size. Aneurysms in these territories can result from median arcuate ligament compression with altered flow mechanics and increased intravascular pressure from retrograde flow through the pancreatic arcades. As in the SMA, adequate collateral flow should be demonstrated before intervention. In a large retrospective study of GDA aneurysms, 52% of patients presented with gastrointestinal hemorrhage, with 40% of those ruptures leading to death. Only 7.5% were asymptomatic.19
Inferior Mesenteric Artery Inferior mesenteric artery (IMA) aneurysms are extremely rare, with few reports in the literature.20 IMA aneurysms most commonly occur in the proximal IMA trunk. IMA aneurysms are more common in men, and most are due to atherosclerosis. Of the known cases, 21 are associated with occlusion of the celiac and the SMA.20,21 Symptoms may include abdominal pain and an enlarging mass, although approximately half of cases are asymptomatic. Because of the rarity of the condition, rupture rates are not known; however, rupture has been demonstrated.20
Workup or Contraindications Multiple imaging modalities may reveal the presence of a VAA or VAPA. Angiography, plain radiographs, ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) have been used to arrive at the diagnosis.5,14 Diagnostic workup for both elective and urgent interventions are similar and include imaging characterization of the aneurysm. Some authors advocate for duplex US and computed tomography angiography in
J.H. Hemp and S.S.Sabri elective cases and for computed tomography angiography in hemodynamically stable but urgent cases, to evaluate the visceral collateral arterial circulation.22 Clinical workup includes a detailed history, focused physical examination, and recent blood analysis including complete blood (cell) count, international normalized ratio, creatine, glomerular filteration rate, platelets, partial thromboplastin time, and C-reactive protein.13 Consent must be obtained. Ideally, the patient is recommended to have nothing by mouth for 6 hours. Intravenous access is necessary for fluid resuscitation and conscious sedation.13 Absolute contraindications to endovascular intervention include hemodynamic instability that cannot be corrected or life-threatening anaphylaxis to contrast. It is worth noting that an acute rupture, especially in the retroperitoneum, may stabilize because of tamponade from surrounding hematoma and does not preclude endovascular treatment.23
Endovascular Management Methods General Technical Considerations Interventions for visceral aneurysms are usually performed from a common femoral arterial access. Brachial or radial arterial access can be considered when the targeted mesenteric vessel takes off the aorta at a steep angle. This access can also be helpful when median arcuate compression of the SMA or the celiac is present. Selective catheterization can be performed using a variety of selective angiographic catheters. The fluoroscopic frame rate during digital subtraction angiography can be adjusted to be 4-6 frames per second to allow visualization of the arterial branches feeding the aneurysm. The need to place a sheath in the mesenteric artery depends on the type of intervention performed and the stability of the catheter system in the mesenteric vasculature. If a sheath is required, a long sheath (eg, Ansel, Raabe Flexor sheaths, Cook Inc., Bloomington, IN) is recommended to be placed in the aorta before selective catheterization of the mesenteric artery. A stiff wire (Rosen or Amplatz, Cook Inc., Bloomington, IN) can be placed through the 5-F catheter, and the sheath can be advanced over the stiff wire into the mesenteric artery origin using the 5-F catheter as a “dilator,” or by exchanging the 5-F catheter for the sheath dilator before advancing into the ostium. To aid in advancing the stiff wire into the mesenteric branch to be treated (eg, the splenic artery), the selective 5-F catheter can be advanced into the middle or distal splenic artery over a hydrophilic wire (Glidewire, Terumo). The stiff wire is then advanced through the 5-F catheter. If the 5-F selective catheter could be advanced deep into the splenic artery, it can be exchanged for a 4-F hydrophilic catheter (Slip-Cath, Cook Inc, or Glidecath, Terumo), which can be advanced into the distal artery over a hydrophilic wire. Simmons 2 and 3 catheters (Angiodynamics) can also be helpful in gaining “purchase” into the distal artery before the stiff wire is placed. A detailed description of different
Endovascular management of visceral aneurysms
17
Figrue 1 The suggested algorithm for treating visceral aneurysms and pseudoaneurysms. (Color version of figure is available online.)
endovascular techniques used to treat VAAs and VAPAs is given later. The choice of the technique relies on the need to preserve the parent artery, the morphology of the aneurysm, and the tortuosity of the parent artery (Fig. 1).
Isolation Isolation includes embolization of the aneurysmal artery, first distal and then proximal to the location of the aneurysm, the so-called sandwich technique. Careful evaluation of the angiographic images is critical to determine all inflow and outflow arteries of the aneurysm. Successful isolation of the aneurysm is dependent on successful embolization of all inflow and outflow arteries. Depending on the vessel size and tortuosity, a 0.035-in system or microembolization system can be chosen. A 0.035-in system is used for larger arteries (43 mm) with a more proximally located aneurysm with single inflow and outflow. This can be achieved by using metallic coils or vascular plugs (VPs). 0.035-in Metallic Coils The selective angiographic catheter of 4 or 5 F is used to select the mesenteric artery and is then advanced over a hydrophilic wire (Glidewire, Terumo, Somerset, NJ) distal to the aneurysm. If this cannot be achieved, then the selective catheter can be exchanged for a hydrophilic catheter (Slip-Cath, Cook Inc., Bloomington, IN, or Glidecath, Terumo, Somerset, NJ), which can be placed distal to the aneurysm. A sheath can be placed in the origin
of the mesenteric artery to aid in the stability of the catheter during embolization. The coils are sized with 10%-20% oversizing compared with the size of the target artery. A variety of pushable metallic coils (Tornado and Nester, Cook Inc., Bloomington, IN, and Vortex, Boston Scientific, Marlborough, MA) can be used. Detachable coils (eg, Interlock, Boston Scientific, Marlborough, MA) can be used especially in more tortuous arteries, where the operator thinks the catheter may not be stable in position. Pushable Hydrogel coils (Terumo, Somerset, NJ) have also been used and have the advantage of being more thrombogenic because of the presence of the hydrogel that may achieve embolization with fewer coils. Vascular Plugs VPs (AMPLATZER Vascular Plug [AVP], AGA Medical, Plymouth, MN) have been used as an alternative embolization method. Advantages of the VP include easy delivery, a detachable system, and the ability to occlude the artery with a single device. Disadvantages include the need for a larger delivery system compared with using metallic coils. The size of the VP ranges from 4-22 mm. Depending on the size of the VP used, a sheath of 5-7 F is required. The success of this procedure relies on the ability to place the sheath distal to the aneurysm. The technical aspects of advancing the sheath are described earlier. The VP is oversized 20%-40% compared with the target artery. We placed 1 or 2 VPs distal to the aneurysm. Once angiography confirms occlusion of the distal artery, the sheath is retracted across the aneurysm and 1 or 2 VPs are deployed
J.H. Hemp and S.S.Sabri
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Figure 2 Isolation technique. (A) Selective splenic angiogram shows a large splenic aneurysm (arrow). A sheath (arrowheads) is placed in the celiac axis for stability. (B) A microcatheter was placed in one of the outflow vessels (arrow). The sheath was advanced into the origin of the splenic artery (arrowheads). (C) Coil embolization of the outflow arteries was performed with microcoils (arrows). (D) After coiling the splenic artery proximal to the aneurysm, there is stagnation of contrast agent in the aneurysm (arrow), indicating successful isolation.
proximal to the aneurysm. Metallic coils can be used in addition to the VP if there is flow into the aneurysm. A new VP (AVP 4, AGA, Plymouth, MN) is now available that can be placed through a catheter of 4-5 F. The size for AVP 4 ranges from 4-8 mm. This VP can be used alone or in combination with metallic coils. Microcoils Similar to the 0.035-in metallic coils, the microcoils need to be placed in the arterial segment(s) distal and then proximal to the aneurysm. This can be achieved by advancing a microcatheter through the selective catheter of 4-5 F placed in the proximal mesenteric artery. The microcatheter is advanced with the aid of a microwire (0.014-0.25 in) in the arterial segment distal to the aneurysm. A long sheath rarely needs to be placed at the
ostium of the mesenteric artery. One of the advantages of microcoils is the availability of varying sizes of coils ranging from 2-25 mm, both in pushable and detachable forms. Using a microcatheter system allows for treatment of a wide range of aneurysm sizes, and its low profile allows for navigating tortuous arterial anatomy, which can be challenging using a 0.035-in system or VPs (Fig. 2).
Covered Stents To preserve the arterial segment where the aneurysm is present, a covered stent can be placed across the aneurysm (Fig. 3). A long sheath is required to deliver the stent in the mesenteric artery. The sheath is advanced into the ostium of the mesenteric artery or further into the target artery to achieve further stability and allow for tracking of the stent
Endovascular management of visceral aneurysms
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Figure 3 Covered stent and coils to treat a splenic aneurysm. (A) Splenic angiogram shows a distal splenic aneurysm (arrows). It can be noted that a sheath is placed in the splenic artery (arrowheads). (B) The smaller of the 2 outflows was embolized using 0.035-in coils (arrow). The larger outflow artery remains patent (arrowheads). (C) A covered stent (black arrow) was placed across the aneurysm into the larger outflow artery (white arrow).
across the aneurysm. It is recommended to extend the stent at least 10 mm proximal and distal to the aneurysm. Selfexpanding covered stents are recommended to be placed in tortuous arteries (Fig. 4), whereas balloon-expandable covered stents (iCast, Atrium/MAQUET Cardiovascular, Wayne, NJ) can be placed in straight proximal segments of mesenteric arteries. Self-expanding stents such as VIABAHN (W.L. Gore, Flagstaff, AZ) range in size from 5-13 mm and require a sheath of 6-12 F, depending on size. A lower profile VIABAHN stent is now available, deliverable over a 0.018-in wire. This allows for better tracking and need for a lower size sheath. Other self-expanding covered stents include Fluency (Bard, Murray Hill, NJ), which is deployable through a 9-F sheath and has a size range of 8-12 mm.
Coil Packing Coil packing of the aneurysm is used to treat saccular true aneurysms with narrow necks. This technique should not be
used for pseudoaneurysms, as the aneurysm sac continues to expand after coil packing because of the absence of a true vessel wall. Tight packing of the coil mass is critical to achieve technical success for this procedure. Embolization is usually preformed through a microcatheter that is placed in the aneurysm sac. Detachable coils are recommended in this setting, as they provide the most controlled and accurate deployment. 3-dimensional detachable framing coils are usually placed first, and they are sized to match the largest diameter of the aneurysm. Then, smaller framing coils are placed followed by helical-shaped coils of progressively smaller size till tight coil packing is achieved. The entire aneurysm needs to be coiled to prevent recanalization (Fig. 5). Fluoroscopic techniques such as road map and other digital subtraction techniques are useful in visualizing the coils as they are deployed and aid in achieving accurate deployment. Attention needs to be given to avoid herniation of coil material into the parent artery. Detachable coils allow for retraction and repositioning in this setting. If the neck of
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J.H. Hemp and S.S.Sabri
Figure 4 Covered stent to treat a pseudoaneurysm secondary to pancreatitis. (A) Splenic angiogram shows a pseudoaneurysm (arrow) with a jet of contrast agent noted arising from the midsplenic artery. (B) Exclusion of the pseudoaneurysm after placement of a covered stent (arrow).
Figure 5 Coil packing technique. (A) Superior mesenteric angiogram shows an inferior pancreaticoduodenal artery aneurysm (black arrows) in a patient with median arcuate compression of the celiac artery. It can be noted that the outflow of the aneurysm is through the posterior inferior pancreaticoduodenal artery (white arrow). The anterior inferior pancreaticoduodenal artery (white arrowheads) is the main collateral pathway to reconstitute the celiac artery. (B) A sheath (white arrowheads) is placed in the origin of the SMA. A microcatheter (white arrow) is advanced into the outflow artery. A “buddy” 0.014-in wire was placed in the SMA to provide support. (C) Superiomesenteric angiogram shows successful coil packing (black arrow) of the aneurysm and continued filling of the celiac artery (white arrow) through pancreaticoduodenal collaterals.
Endovascular management of visceral aneurysms
Figure 6 Stent-assisted coiling technique. Early (A) and late (B) phases of aortogram and selective angiogram of the aneurysm (C) show a replaced right hepatic artery aneurysm (black arrow). The 2 outflow arteries are replaced right hepatic artery (black arrowheads) and an inferior pancreaticoduodenal artery that reconstitutes the celiac artery (white arrow). (D) A sheath and a diagnostic catheter were advanced through the gastroduodenal artery (black arrow) into the pancreaticoduodenal artery to aid in coiling the aneurysm and the outflow arteries. (E) Replaced right hepatic arteriogram shows a bare metal stent in place (large black arrow) with successful coil packing of the aneurysm (large white arrow). The pancreaticoduodenal artery branches were embolized with microcoils (small black arrows) and a vascular plug (white arrow).
21
J.H. Hemp and S.S.Sabri
22
Figure 7 Liquid embolic agents in tortuous arteries. (A) Splenic angiogram shows an extremely tortuous splenic artery with multiple aneurysms of varying sizes (black arrows). (B) The aneurysms were excluded using a combination of coils and onyx (black arrows).
the aneurysm is too wide, stent-assisted coiling can be performed. For this technique, a bare metal stent is placed across the saccular aneurysm in the parent artery (Fig. 6). Through the interstices of the stent, a microcatheter can be placed into the sac, and coil packing can be performed without the risk of herniation into the parent artery. Alternatively, the microcatheter can be placed in the aneurysm sac before stent deployment. The stent is then deployed alongside the microcatheter over a “buddy” wire. The advantage of this technique is that it guarantees access into the aneurysm sac. The disadvantage is the need for a larger sheath to accommodate a microcatheter alongside the bare metal stent.
Liquid Embolic Agents Liquid embolic agents such as n-butyl cyanoacrylate glue and onyx can be used to embolize the inflow and outflow arteries or filling the aneurysm sac itself. A useful application is in extremely tortuous arteries, where pushability of coils is limited (Fig. 7). Liquid agents can be injected through the microcatheter first in the distal artery(ies) until complete filling of the target artery(ies) is noted. The catheter can be retracted to the artery proximal to the aneurysm, which can be embolized using liquid agents or coils. Alternatively, the aneurysm sac can be filled with liquid agents, if preservation of the parent artery is planned. However, spillage of liquid agents into the parent artery is a risk, and careful incremental injection of liquid agents is recommended. A balloon-assisted technique can be used. A balloon is placed in the parent artery across the aneurysm sac alongside a microcatheter placed in the aneurysm sac. Liquid agents can be injected directly into the sac. The balloon prevents spillage of liquid agent. However, overfilling should be avoided, as spillage can still occur after balloon deflation.
Percutaneous Thrombin Injection Thrombin can be injected directly into the sac to aid in thrombosis. This technique is particularly useful in mesenteric artery pseudoaneurysms and especially if the aneurysm neck is narrow and long. The concept is similar to thrombin injection to treat femoral pseudoaneurysms after arterial puncture. Access into the sac can be transarterial by placing a microcatheter into the aneurysm sac and injecting incremental amounts of thrombin until stasis is confirmed by transabdominal US or by performing angiogram from the parent artery. Alternatively, access into the sac can be achieved percutaneously using CT, US, or fluoroscopy guidance. If the neck is wide or short, balloon-assisted thrombin injection can be performed with a balloon inflated across the aneurysm neck in the parent artery during thrombin injection. The major disadvantage of thrombin is that it is not radiopaque and distal embolization may not be recognized during the procedure.
Outcomes, Complications, and Follow-up Historically, open resection or ligation of visceral aneurysms has been the gold standard for treatment of VAAs and VAPAs; however, endovascular methods have been increasingly used with excellent results and offer an effective alternative therapy for poor surgical candidates. Although most reports in the literature are smaller series, the largest studies have demonstrated technical success rates ranging from 89%-98%.1,6,24 Studies have also demonstrated that there is no significant difference in the morbidity and mortality rates between open and endovascular methods and that the reintervention rate between surgery and endovascular treatments is not different.
Endovascular management of visceral aneurysms Studies have also demonstrated decreased hospital stay, when compared with surgical repair, with a mean hospital stay of 3.8 vs 12 days. A significant difference in survival between aneurysms treated electively vs urgently underscores the need for early, elective intervention.7,24 Observed complications have been minor in general. As with any procedure that requires arterial access, there is a risk of access-related complications such as groin hematoma, retroperitoneal hematoma, femoral artery pseudoaneurysm, femoral artery thrombosis, or embolism. The possibility of contrast agent–induced nephropathy must be considered in those with poor renal function; however, CO2 can be used in some situations as an alternative contrast agent.1 Specific to treatment of splenic artery aneurysms, splenic infarcts and postembolization syndrome has been observed in up to 40% of patients and are more often associated with distal splenic artery aneurysms. In general, the condition is often self-limited and managed with pain medications.3,6,24 Specific to the treatment of hepatic artery aneurysms, there is a risk of hepatic ischemia, hepatic abscess, and cholecystitis.4 Treatment failures including persistent perfusion, recanalization, and coil migration have been observed, with reperfusion rates of 10.3% in the first month.1,4,16 Failures may be related to technical difficulties in catheterizing the aneurysm neck, resulting in intraprocedural dissection or rupture, and may be more frequently encountered with treatment of large aneurysms, as large neck size and turbulence can lead to unstable coils and incomplete sac packing.7,18 In the setting of the isolation technique for saccular aneurysms, there is a risk of coil migration into the pseudoaneurysm with associated growth in sac size. While using stents, there is a risk of stent migration or stent occlusion requiring reintervention.7 Pseudoaneurysms are particularly prone to recurrent bleeding due to pancreatitis or other persistent inflammatory states.6 The potential for early and late failure such as growth in sac size or leak, which would require reintervention, necessitates early and serial imaging follow-up.11 Unfortunately, the same radiopaque materials that allow fluoroscopic visualization and endovascular treatment often preclude sensitive CT evaluation because of artifact.1 Some authors advocate for the use of contrast-enhanced US or MRI to verify complete aneurysmal sac occlusion.16 Proposed imaging protocols include followup imaging in 1 week to 30 days; CT follow-up at 1, 6, and 12 months; and yearly CT or MRI.7,9,12,16 In summary, endovascular treatment of aneurysms and pseudoaneurysms is technically feasible with excellent outcomes, lower morbidity, and shorter hospital stay than open procedures are. Interventional radiologists should be familiar with the diagnosis, general indications, and specific techniques of endovascular treatment of visceral artery aneurysms and pseudoaneurysms as discussed earlier. Additionally, interventionalists should also be aware that anatomical variation necessitates an artery-specific treatment approach. The choice of technique relies on the need to preserve the parent artery, the morphology of the aneurysm, and the tortuosity of the parent artery, as presented in the suggested treatment algorithm. Techniques discussed
23 include isolation, covered stent, coil packing, liquid embolic agents, and percutaneous thrombin injection.
References 1. Tulsyan N, Kashyap VS, Greenberg RK, et al: The endovascular management of visceral artery aneurysms and pseudoaneurysms. J Vasc Surg 45:276-283, 2007 2. Cordova AC, Sumpio BE: Visceral artery aneurysms and pseudoaneurysms—Should they all be manage by endovascular techniques? Ann Vasc Dis 6:687-693, 2013 3. Abbas MA, Stone WM, Fowl RJ, et al: Splenic artery aneurysms: Two decades of experience at Mayo clinic. Ann Vasc Surg 16:442-449, 2002 4. Abbas MA, Fowl RJ, Stone WM, et al: Hepatic artery aneurysm: Factors that predict complications. J Vasc Surg 38:41-45, 2003 5. Stone WM, Abbas M, Cherry KJ, et al: Superior mesenteric artery aneurysms: Is presence an indication for intervention? J Vasc Surg 36:234-237, 2002 6. Gabelmann A, Gorich J, Merkle E: Endovascular treatment of visceral artery aneurysms. J Endovasc Ther 9:38-47, 2002 7. Ferrero E, Ferro M, Viazzo A, et al: Visceral artery aneurysms, an experience on 32 cases in a single center: Treatment from surgery to multilayer stent. Ann Vasc Surg 25:923-935, 2011 8. Kasirajan K, Greenberg RK, Clair D, et al: Endovascular management of visceral artery aneurysm. J Endovasc Ther 8:150-155, 2001 9. Fankhauser GT, Stone WM, Naidu SG, et al: The minimally invasive management of visceral artery aneurysms and pseudoaneurysms. J Vasc Surg 53:966-970, 2011 10. Nosher JL, Chung J, Brevetti LS, et al: Visceral and renal artery aneurysms: A pictorial essay on endovascular therapy. Radiographics 26:1687-1704, 2006 11. Berceli SA: Hepatic and splenic artery aneurysms. Semin Vasc Surg 18:196-201, 2005 12. Sachdev-Ost U: Visceral artery aneurysms: Review of current management options. Mt Sinai J Med 77:296-303, 2010 13. Kos S, Liu DM, Jacob AI: Mesenteric aneurysms. in Geshwind JH, Dake MD (eds.), Abrams’ Angiography. Philadelphia, PA: Lippincott Williams & Wilkins, 712-722, 2006 14. Stone WM, Abbas MA, Gloviczki P, et al: Celiac arterial aneurysms. Arch Surg 137:670-674, 2002 15. Waldenberger P, Bendix N, Peterson J, et al: Clinical outcome of endovascular therapeutic occlusion of the celiac artery. J Vasc Surg 46:655-661, 2007 16. Lagana D, Carrafiello G, Mangini M, et al: Multimodal approach to endovascular treatment of visceral artery aneurysms and pseudoaneurysms. Eur J Radiol 59:104-111, 2006 17. Kueper MA, Ludescher B, Koenigsrainer I, et al: Successful coil embolization of a ruptured gastroduodenal artery aneurysm. Vasc Endovasc Surg 41:568-571, 2008 18. Marone EM, Mascia D, Kahlberg A, et al: Is open repair still the gold standard in visceral artery aneurysm management? Ann Vasc Surg 25:936-946, 2011 19. Habib N, Hassan S, Abdou R, et al: Gastroduodenal artery aneurysm, diagnosis, clinical presentation and management: A concise review. Ann Surg Innov Res 7:4, 2013 20. Edogawa S, Shibuya T, Kurose K, et al: Inferior mesenteric artery aneurysm: Case report and literature review. Ann Vasc Dis 6:98-101, 2013 21. Tsukioka K, Nobara H, Nishimura K: A case of inferior mesenteric artery aneurysm with an occlusive disease in superior mesenteric artery and the celiac artery. Ann Vasc Dis 3:160-163, 2010 22. Ferrero E, Viazzo A, Ferri M, et al: Management and urgent repair of ruptured visceral artery aneurysms. Ann Vasc Surg 25:e7-e11, 2011 23. Jackson JE: Management of visceral aneurysms. in Mauro MA (ed.), Image-Guided Interventions. Philadelphia, PA: Saunders, 851-862, 2014 24. Sachdev U, Baril DT, Ellozy SH, et al: Management of aneurysms involving the branches of the celiac and superior mesenteric arteries: A comparison of surgical and endovascular therapy. J Vasc Surg 44:718-723, 2006