Internal Iliac Artery Embolization as an Adjunct to Endovascular Aneurysm Repair Jos C. van den Berg An important requirement for endovascular aortic or iliac aneurysm repair is the presence of an adequate distal landing zone in the common iliac artery. Aneurysmal aortas are associated with dilated common iliac arteries in about 20% of patients, making patients ineligible for standard endovascular repair. Because of the limit of a maximum diameter of commercially available iliac limbs, patients with large-diameter common iliac arteries do not have a sufficient landing zone and therefore require extension of the stent graft into the external iliac artery and embolization of the internal iliac artery (IIA) to prevent retrograde flow into the aneurysm from the IIA and thus a type II endoleak. Although larger (aortic) cuffs can be used (bell-bottom technique), a common iliac artery larger than 22 mm in diameter is considered a diseased landing zone, prone to further dilation and a potential source of subsequent type I endoleak. Furthermore, the presence of mural thrombus within the dilated common iliac artery can increase the risk of distal thromboembolism. Preventing a type II endoleak in this setting can be achieved by embolization of the IIA or by surgical ligation. When a short segment of the common iliac artery proximal to the iliac bifurcation has a diameter small enough to allow sealing but not to allow endograft fixation, extension of the iliac limb into the external iliac artery (with an oversizing of 10%–15% in the distal common iliac artery) may be performed without prior embolization of the IIA. Alternatively, surgical reimplantation may be performed or bifurcated stent grafts or covered stents can be used to preserve flow into the IIA. This leads to less common occurrence of buttock claudication and may therefore be considered a primary choice in younger patients with suitable anatomy. Pretreatment embolization usually involves occluding one or both internal iliac arteries in order to be able to expand the anatomic inclusion criteria to perform endovascular treatment of aortoiliac aneurysms extending up to or beyond the iliac bifurcation. Indications for IIA occlusion are extension of the AAA into the common iliac artery with an insufficient distal neck, aneurysms involving the IIA, and insufficient distal landing zone. Relevant Anatomy The IIA is the major blood supply to the gluteal area through its posterior division. The anterior division supplies the rectosigmoid and genital areas. It provides a communication between the systemic and visceral circulation through collateral vessels to the superior rectal branch of the inferior mesenteric artery (IMA). The IMA provides the main blood supply to the left colon by way of the left colic artery, sigmoidal branches, and superior rectal artery. Ileocolic and right and middle colic arteries from the superior mesenteric artery communicate with the IMA branches through the marginal artery of Drummond and the arcade of Riolan. Prolonged occlusion of one or two of these systems is usually without any clinical sequelae caused by existence of collaterals. In addition, there are collateral pathways through the lumbar arteries, deep iliac circumflex artery, lateral and medial femoral circumflex artery, and iliolumbar and obturator arteries toward the IIA. The risk of pelvic ischemia increases when both internal iliac arteries and the IMA are occluded simultaneously. Such sudden interruption of flow can lead to severe complications. Embolization Tools Embolization can be performed by using coils or a vascular occlusion plug. Coils are available in various sizes (length and diameter) and shapes (spiral/helical versus complex) and with or without polyester (Dacron) fibers. Hydrocoils are coated with a gel that, once placed in a buffered solution (e.g., blood), takes up water into the polymer matrix after about 5 minutes, resulting in volumetric expansion. This results in a better filling of the vascular space and use of fewer coils. Coils can be placed by means of various delivery systems, including placement by using a coil pusher or guidewire versus use of detachable coil systems. There is no place for the use of glue (such as cyanoacrylate, Ethibloc, and Onyx), or microspheres (polyvinyl alcohol or trisacryl gelatin microspheres) in preoperative embolization. Pushable Coils Since the original stainless steel coils were introduced, a lot of modifications have been made. Currently, most of the commercially available coils are made of platinum and come in standard sizes of 0.035 inch and 0.038 inch. Microcoils are available in a coil thickness of 0.018 inch. An advantage of the platinum coils is their compatibility with magnetic resonance imaging (MRI) in patients in whom follow-up of the stent graft will be by MRI. Coils are advanced using a coil-pusher wire or a guidewire. When using a guidewire (which has a slightly tapered tip) in combination with large-lumen microcatheters (>0.018 inch) there is a risk of the wire becoming trapped between the coil and the inner side of the microcatheter, thus locking the coil and guidewire within the catheter. Alternatively, the squirt technique can be used: After the coil is loaded into the (micro)catheter, a saline-filled Luer-lock syringe (2 or 3 mL) is connected to the (micro)catheter, and the (micro)coil is advanced under fluoroscopic guidance through the catheter by administering small boluses of saline. This technique can only be used in cases where an extremely stable catheter position has been obtained, and it should never be the delivery technique for placing the first coil in a large target vessel. Detachable Coils Detachable coils developed for applications in neurointerventional radiology are also used in peripheral interventions. The availability of coils in long lengths and in various complex shapes, combined with the possibility to reposition them before final release, makes them extremely useful in procedures where accurate embolization of high-flow, large-diameter vessels is needed. Release of detachable coils can be accomplished using various techniques that vary with type and manufacturer of the coils. Release mechanisms commonly used are electrolytic release, pressure-controlled release, and mechanical detachment, using either an interlocking release mechanism or a torsion-controlled detachment. Vascular Occlusion Plug Currently there is only one commercially available peripheral vascular occlusion plug (Amplatzer vascular plug, AGA Medical, Golden Valley, MN). The device is similar to the PFO (patent foramen ovale) occlusion devices and consists of a cylindrical device made from a self-expandable nitinol wire mesh. Radiopaque platinum marker bands are embedded in the proximal and distal ends. The plug is attached to a 135-cm-long delivery cable and can be released by a microscrew mechanism. Several types of plug are available: Vascular Plug (AVP I), Vascular Plug II (AVP II), and Vascular Plug 4, each having different shapes. Diameters range from 3 mm to 22 mm. Crossing profile (i.e., the minimum required inner diameter of sheath/guiding catheter) of the device is from 0.038 inch for smaller diameters (4-Fr catheter) to 0.098 inch (7-Fr sheath) for plugs with a larger diameter. Technique Embolization of Internal Iliac Arteries To prevent retrograde flow into the aneurysm, the most proximal nonaneurysmal part of the IIA should be occluded. It is important to occlude only the main trunk of the IIA and leave the communication between the anterior and posterior branches of the IIA open. This approach reduces the number of ischemic complications. The relative risk of developing claudication after distal embolization in one series has been reported to be 4.6 times higher after proximal embolization. Most interventionalists favor a staged procedure, performing the embolization before the EVAR, to reduce use of contrast material and operative time. Other reasons to perform a staged procedure are the lack of high-quality fluoroscopy in the operative setting, which can hamper navigation with microcatheters (with the advent of high-end hybrid operating rooms, this is less of an issue), and a local reimbursement system that favors outpatient embolization treatment. Finally, there is an increased likelihood of developing transient buttock claudication when performing a concomitant one-stage procedure. Patients with impaired renal function are preferably treated with a staged procedure. When both internal iliac arteries need to be occluded preoperatively, sequential bilateral embolization would reduce the risk of developing complications intuitively. It was shown only in one study that simultaneous embolization of both internal iliac arteries can be performed with a complication rate comparable to that from other reports where a staged procedure was performed. Published series are small, however, and to date it is not clear whether there are advantages of staged versus simultaneous embolization, and controversy persists. Coils Coils should be oversized about 15% to 20% with respect to the target vessel to prevent distal migration of the device. Overly large coils potentially can displace the catheter from its selected location. This is especially so when stainless steel coils (with a higher radial force) and platinum macrocoils are used. The lower radial force of platinum microcoils allows the coil to be adapted even in cases of extreme oversizing (>50%), without the risk of catheter displacement. Although coils can be placed using a selective diagnostic catheter (lumen 0.035 inch), a coaxial catheter system is preferable. Using the coaxial technique, the diagnostic catheter needs to have a lumen of 0.038 inches in order to allow passage of a microcatheter. The most commonly used selective catheters are cobra-curved or Simmons-type catheters. The microcatheter should be inserted into the main catheter by means of a Y-connecter, which allows a continuous heparinized saline flush of the diagnostic catheter throughout the procedure. The main advantage of using a coaxial system is the stability provided by the diagnostic catheter, allowing movement of the microcatheter within the diagnostic catheter. These movements are needed for (some of) the packing techniques described hereafter. The goal of embolization is to produce a permanent occlusion of the target vessel. Placement of coils in an elongated fashion provides only temporary occlusion, and therefore a cross-sectional coil occlusion should be attempted with densely packed coils. Elongation of coils (either pushable or detachable) can be avoided by slowly retracting the microcatheter while moving its tip back and forth during deployment of the coil, resulting in a weaving-like pattern. When dealing with large-diameter target vessels such as the IIA, the risk of distal migration of the first coil beyond the main trunk bifurcation can be reduced by using the scaffold technique or the anchor technique. With the scaffold technique, a stable matrix is formed first, either by deploying high-radial-force pushable coils or (preferably) detachable coils (with a complex, rather than helicoid, shape). The advantage of using detachable coils is the possibility to withdraw the coil in case of distal migration (usually caused by undersizing of the coil) and to correct coil position or to change the diameter of the first coil to be placed. After this scaffold (or endoskeleton or nest) is created, complete cross-sectional occlusion is obtained by weaving smaller (fibered) coils into the remaining interstices as described earlier. Alternatively, in cases where instability of the first coil is anticipated, the anchor technique can be used (specifically when detachable coils are not available). With this technique, the main catheter is placed in the target vessel to be occluded and the microcatheter is advanced into a small side branch. Subsequently a (long) coil is placed for 1 cm to 2 cm in the side branch, the microcatheter is withdrawn, and the rest of the coil is placed more proximally. Then complete packing is achieved by deploying multiple smaller coils. Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related Related posts: Embolic Protection Devices to Prevent Stroke during Percutaneous Angioplasty and Stenting Management of Acute Limb Ischemia Complicating Aortic Reconstruction Treatment of Dyslipidemia and Hypertriglyceridemia Intraoperative Assessment of the Technical Adequacy of Carotid Endarterectomy Stay updated, free articles. Join our Telegram channel Join Tags: Current Therapy in Vascular and Endovascular Surgery Aug 25, 2016 | Posted by admin in CARDIOLOGY | Comments Off on Internal Iliac Artery Embolization as an Adjunct to Endovascular Aneurysm Repair Full access? Get Clinical Tree
Internal Iliac Artery Embolization as an Adjunct to Endovascular Aneurysm Repair Jos C. van den Berg An important requirement for endovascular aortic or iliac aneurysm repair is the presence of an adequate distal landing zone in the common iliac artery. Aneurysmal aortas are associated with dilated common iliac arteries in about 20% of patients, making patients ineligible for standard endovascular repair. Because of the limit of a maximum diameter of commercially available iliac limbs, patients with large-diameter common iliac arteries do not have a sufficient landing zone and therefore require extension of the stent graft into the external iliac artery and embolization of the internal iliac artery (IIA) to prevent retrograde flow into the aneurysm from the IIA and thus a type II endoleak. Although larger (aortic) cuffs can be used (bell-bottom technique), a common iliac artery larger than 22 mm in diameter is considered a diseased landing zone, prone to further dilation and a potential source of subsequent type I endoleak. Furthermore, the presence of mural thrombus within the dilated common iliac artery can increase the risk of distal thromboembolism. Preventing a type II endoleak in this setting can be achieved by embolization of the IIA or by surgical ligation. When a short segment of the common iliac artery proximal to the iliac bifurcation has a diameter small enough to allow sealing but not to allow endograft fixation, extension of the iliac limb into the external iliac artery (with an oversizing of 10%–15% in the distal common iliac artery) may be performed without prior embolization of the IIA. Alternatively, surgical reimplantation may be performed or bifurcated stent grafts or covered stents can be used to preserve flow into the IIA. This leads to less common occurrence of buttock claudication and may therefore be considered a primary choice in younger patients with suitable anatomy. Pretreatment embolization usually involves occluding one or both internal iliac arteries in order to be able to expand the anatomic inclusion criteria to perform endovascular treatment of aortoiliac aneurysms extending up to or beyond the iliac bifurcation. Indications for IIA occlusion are extension of the AAA into the common iliac artery with an insufficient distal neck, aneurysms involving the IIA, and insufficient distal landing zone. Relevant Anatomy The IIA is the major blood supply to the gluteal area through its posterior division. The anterior division supplies the rectosigmoid and genital areas. It provides a communication between the systemic and visceral circulation through collateral vessels to the superior rectal branch of the inferior mesenteric artery (IMA). The IMA provides the main blood supply to the left colon by way of the left colic artery, sigmoidal branches, and superior rectal artery. Ileocolic and right and middle colic arteries from the superior mesenteric artery communicate with the IMA branches through the marginal artery of Drummond and the arcade of Riolan. Prolonged occlusion of one or two of these systems is usually without any clinical sequelae caused by existence of collaterals. In addition, there are collateral pathways through the lumbar arteries, deep iliac circumflex artery, lateral and medial femoral circumflex artery, and iliolumbar and obturator arteries toward the IIA. The risk of pelvic ischemia increases when both internal iliac arteries and the IMA are occluded simultaneously. Such sudden interruption of flow can lead to severe complications. Embolization Tools Embolization can be performed by using coils or a vascular occlusion plug. Coils are available in various sizes (length and diameter) and shapes (spiral/helical versus complex) and with or without polyester (Dacron) fibers. Hydrocoils are coated with a gel that, once placed in a buffered solution (e.g., blood), takes up water into the polymer matrix after about 5 minutes, resulting in volumetric expansion. This results in a better filling of the vascular space and use of fewer coils. Coils can be placed by means of various delivery systems, including placement by using a coil pusher or guidewire versus use of detachable coil systems. There is no place for the use of glue (such as cyanoacrylate, Ethibloc, and Onyx), or microspheres (polyvinyl alcohol or trisacryl gelatin microspheres) in preoperative embolization. Pushable Coils Since the original stainless steel coils were introduced, a lot of modifications have been made. Currently, most of the commercially available coils are made of platinum and come in standard sizes of 0.035 inch and 0.038 inch. Microcoils are available in a coil thickness of 0.018 inch. An advantage of the platinum coils is their compatibility with magnetic resonance imaging (MRI) in patients in whom follow-up of the stent graft will be by MRI. Coils are advanced using a coil-pusher wire or a guidewire. When using a guidewire (which has a slightly tapered tip) in combination with large-lumen microcatheters (>0.018 inch) there is a risk of the wire becoming trapped between the coil and the inner side of the microcatheter, thus locking the coil and guidewire within the catheter. Alternatively, the squirt technique can be used: After the coil is loaded into the (micro)catheter, a saline-filled Luer-lock syringe (2 or 3 mL) is connected to the (micro)catheter, and the (micro)coil is advanced under fluoroscopic guidance through the catheter by administering small boluses of saline. This technique can only be used in cases where an extremely stable catheter position has been obtained, and it should never be the delivery technique for placing the first coil in a large target vessel. Detachable Coils Detachable coils developed for applications in neurointerventional radiology are also used in peripheral interventions. The availability of coils in long lengths and in various complex shapes, combined with the possibility to reposition them before final release, makes them extremely useful in procedures where accurate embolization of high-flow, large-diameter vessels is needed. Release of detachable coils can be accomplished using various techniques that vary with type and manufacturer of the coils. Release mechanisms commonly used are electrolytic release, pressure-controlled release, and mechanical detachment, using either an interlocking release mechanism or a torsion-controlled detachment. Vascular Occlusion Plug Currently there is only one commercially available peripheral vascular occlusion plug (Amplatzer vascular plug, AGA Medical, Golden Valley, MN). The device is similar to the PFO (patent foramen ovale) occlusion devices and consists of a cylindrical device made from a self-expandable nitinol wire mesh. Radiopaque platinum marker bands are embedded in the proximal and distal ends. The plug is attached to a 135-cm-long delivery cable and can be released by a microscrew mechanism. Several types of plug are available: Vascular Plug (AVP I), Vascular Plug II (AVP II), and Vascular Plug 4, each having different shapes. Diameters range from 3 mm to 22 mm. Crossing profile (i.e., the minimum required inner diameter of sheath/guiding catheter) of the device is from 0.038 inch for smaller diameters (4-Fr catheter) to 0.098 inch (7-Fr sheath) for plugs with a larger diameter. Technique Embolization of Internal Iliac Arteries To prevent retrograde flow into the aneurysm, the most proximal nonaneurysmal part of the IIA should be occluded. It is important to occlude only the main trunk of the IIA and leave the communication between the anterior and posterior branches of the IIA open. This approach reduces the number of ischemic complications. The relative risk of developing claudication after distal embolization in one series has been reported to be 4.6 times higher after proximal embolization. Most interventionalists favor a staged procedure, performing the embolization before the EVAR, to reduce use of contrast material and operative time. Other reasons to perform a staged procedure are the lack of high-quality fluoroscopy in the operative setting, which can hamper navigation with microcatheters (with the advent of high-end hybrid operating rooms, this is less of an issue), and a local reimbursement system that favors outpatient embolization treatment. Finally, there is an increased likelihood of developing transient buttock claudication when performing a concomitant one-stage procedure. Patients with impaired renal function are preferably treated with a staged procedure. When both internal iliac arteries need to be occluded preoperatively, sequential bilateral embolization would reduce the risk of developing complications intuitively. It was shown only in one study that simultaneous embolization of both internal iliac arteries can be performed with a complication rate comparable to that from other reports where a staged procedure was performed. Published series are small, however, and to date it is not clear whether there are advantages of staged versus simultaneous embolization, and controversy persists. Coils Coils should be oversized about 15% to 20% with respect to the target vessel to prevent distal migration of the device. Overly large coils potentially can displace the catheter from its selected location. This is especially so when stainless steel coils (with a higher radial force) and platinum macrocoils are used. The lower radial force of platinum microcoils allows the coil to be adapted even in cases of extreme oversizing (>50%), without the risk of catheter displacement. Although coils can be placed using a selective diagnostic catheter (lumen 0.035 inch), a coaxial catheter system is preferable. Using the coaxial technique, the diagnostic catheter needs to have a lumen of 0.038 inches in order to allow passage of a microcatheter. The most commonly used selective catheters are cobra-curved or Simmons-type catheters. The microcatheter should be inserted into the main catheter by means of a Y-connecter, which allows a continuous heparinized saline flush of the diagnostic catheter throughout the procedure. The main advantage of using a coaxial system is the stability provided by the diagnostic catheter, allowing movement of the microcatheter within the diagnostic catheter. These movements are needed for (some of) the packing techniques described hereafter. The goal of embolization is to produce a permanent occlusion of the target vessel. Placement of coils in an elongated fashion provides only temporary occlusion, and therefore a cross-sectional coil occlusion should be attempted with densely packed coils. Elongation of coils (either pushable or detachable) can be avoided by slowly retracting the microcatheter while moving its tip back and forth during deployment of the coil, resulting in a weaving-like pattern. When dealing with large-diameter target vessels such as the IIA, the risk of distal migration of the first coil beyond the main trunk bifurcation can be reduced by using the scaffold technique or the anchor technique. With the scaffold technique, a stable matrix is formed first, either by deploying high-radial-force pushable coils or (preferably) detachable coils (with a complex, rather than helicoid, shape). The advantage of using detachable coils is the possibility to withdraw the coil in case of distal migration (usually caused by undersizing of the coil) and to correct coil position or to change the diameter of the first coil to be placed. After this scaffold (or endoskeleton or nest) is created, complete cross-sectional occlusion is obtained by weaving smaller (fibered) coils into the remaining interstices as described earlier. Alternatively, in cases where instability of the first coil is anticipated, the anchor technique can be used (specifically when detachable coils are not available). With this technique, the main catheter is placed in the target vessel to be occluded and the microcatheter is advanced into a small side branch. Subsequently a (long) coil is placed for 1 cm to 2 cm in the side branch, the microcatheter is withdrawn, and the rest of the coil is placed more proximally. Then complete packing is achieved by deploying multiple smaller coils. Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related Related posts: Embolic Protection Devices to Prevent Stroke during Percutaneous Angioplasty and Stenting Management of Acute Limb Ischemia Complicating Aortic Reconstruction Treatment of Dyslipidemia and Hypertriglyceridemia Intraoperative Assessment of the Technical Adequacy of Carotid Endarterectomy Stay updated, free articles. Join our Telegram channel Join Tags: Current Therapy in Vascular and Endovascular Surgery Aug 25, 2016 | Posted by admin in CARDIOLOGY | Comments Off on Internal Iliac Artery Embolization as an Adjunct to Endovascular Aneurysm Repair Full access? Get Clinical Tree
