General Description

The complications of endovascular interventions for the treatment of cerebrovascular diseases can be related to the inherent risks associated with catheter angiograms and catheter-based interventions, as well as the risks that patients are exposed to secondary to technical components of specific interventions. Here we review many of the most common risks (summarized in Table 40.1 ) and preventive or treatment strategies (summarized in Table 40.2 ) for various complications that may occur during neuroendovascular interventions.

General Complications

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  Contrast-related nephropathy: Acute kidney injury secondary to contrast-induced tubular necrosis is a well-described phenomenon that can be seen shortly after the administration of iodinated contrast material. This is characterized by an increase in the creatinine level between 24 and 48 hours postprocedure, followed by normalization of the level over 3–7 days. Although contrast-induced acute kidney injury is usually benign, in rare circumstances, dialysis may be required. ²⁸

  
  
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  Risks related to conscious sedation/general anesthesia: Cardiovascular and respiratory complications as well as reactions to anesthetic agents are some of the known risks associated with general anesthesia. The risks can be minimized by the use of conscious sedation. As with general anesthesia, cardiovascular and respiratory functions must be closely monitored throughout the duration of the procedure to reduce the incidence of adverse events. Judicious use of sedative and analgesic agents and titration of these agents to the patient’s condition can help to avoid problems with oversedation, such as hypoventilation and hypercapnia. Reversal agents should be readily available in such cases.

  
  
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  Risks associated with radiation: Radiation-induced alopecia is the most common radiation-related concern and is typically a dose-dependent phenomenon. It can manifest as patches of hair falling out in the days to weeks following intensive treatment. Typically, this is self-limiting, and the hair will regrow in time. With higher doses, patients may suffer skin burns. Radiation-induced malignancies may also occur in a more delayed time frame, sometimes years later. To avoid such complications, prolonged procedures benefit from dose-tracking systems that measure the skin dose for the patient and help the physician assess when it may be appropriate to reposition the X-ray sources to distribute the dose over wider areas.

Access Site Complications

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  Access site hematoma ( Fig. 40.1, Video 40.1 ): Hematomas are relatively common at access sites, with risk factors including body habitus, anticoagulant, thrombolytic, or antiplatelet use, and choice of puncture site. Hematomas may develop at the time of access, for instance, if there are multiple punctures, if the back-wall technique is used, or because of failure of hemostatic closure at the completion of the procedure. Hematoma risk may be mitigated with routine use of ultrasound for access, use of smaller gauge needles for initial access, and use of more superficial sites, such as the radial artery. Hematomas may present as apparent bruising under the skin, fullness in the surrounding tissues, with pain, and in extreme cases, with hypotension and bradycardia. Management of hematomas begins with control of bleeding by application of direct pressure. For superficial sites, pressure is usually sufficient, but for persistent bleeds or large-bore punctures, a vascular surgery consultation may be required for direct suture repair or placement of a covered stent over the vessel wall defect.

  
  
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  Retroperitoneal hematoma: The greatest risk for retroperitoneal hematoma comes from a high puncture site for femoral access. Many of the same risk factors previously noted apply here, and routine use of ultrasound or prepuncture fluoroscopy will minimize these risks. Typically, the puncture should be made beneath the equator of the femoral head and an angiographic run of the groin area should indicate that the puncture site is below the inferior epigastric artery, which courses beneath the inguinal ligament and serves as a landmark for entry into the retroperitoneal space. Often there are no overt signs of a retroperitoneal bleed, so patients may lose several units of blood prior to presentation. Hypotension and tachycardia are often the presenting signs. The hematoma can be confirmed with computed tomography (CT) of the abdomen and pelvis. Resuscitation with fluids or blood and use of vasopressors are usually adequate for management, but if there is a large volume or persistent loss of blood, placement of a covered stent for obliteration of the opening may be necessary.

  
  
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  Pseudoaneurysm: Weakness in the arterial wall after access has been obtained can lead to partial-thickness dilation of the vessel. Most pseudoaneurysms present as a palpable mass and are best evaluated with ultrasound imaging and a vascular surgery consultation. Many pseudoaneurysms will spontaneously thrombose and the mass will dissipate over time. Some lesions may require a thrombin injection performed by a vascular surgeon; enlarging and high-flow lesions may require repair with open surgery or covered stenting.

  
  
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  Arterial dissection: Dissection at the access site is generally discovered during routine angiographic runs through the sheath after access has been obtained. If an intimal flap is noted, it is best to obtain a vascular surgery consultation. Non-flow-limiting dissections may not require intervention and can be managed with aspirin. If flow limitation is noted, stenting may be required.

  
  
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  Nerve injury: Poor localization of the vessel, like in a patient with large body habitus or calcified vessels, can make arterial puncture difficult. Medialization of the needle could lacerate or puncture the nerve and lead to pain, numbness, or paresthesias. This is often managed conservatively and will improve with time, although poorly tolerated pain may be successfully managed with gabapentin or pregabalin. Use of ultrasound and careful palpation, especially in patients with difficult anatomy, may help to reduce such injuries.

  
  
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  Infection of the access site or abscess formation: Infections may present as superficial erythema, drainage, or a palpable mass. Ultrasound imaging can be helpful to elucidate the relationship of masses to the artery and can exclude the presence of a pseudoaneurysm. Patients with large body habitus or preexisting superficial infections are particularly prone to infectious complications. In such patients, alternate access sites should be considered. Superficial infections can be successfully managed with oral antibiotics and should be closely monitored for abscess formation. An abscess should be managed aggressively. A vascular surgery consultation should be obtained as surgical drainage and debridement are often required. Wound healing is often an issue for groin abscesses because it is difficult to keep the area clean and dry.

General Procedural Complications

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  Vasospasm: Catheter manipulation can irritate vessels and cause them to constrict. If the vasospasm is flow-limiting, the catheter should be withdrawn to avoid ischemic complications. Vasodilators, such as verapamil, should be slowly infused to relax the vessels before proceeding with the procedure. In peripheral locations, such as when accessing or navigating the radial artery, spasm also responds to topical vasodilators, such as nitroglycerine paste, and to systemic analgesics.

  
  
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  Vessel perforation ( Fig. 40.2, Video 40.2 ): Wire perforations can result from several issues. A build-up of tension in microcatheter systems can result in an uncontrolled release of energy, causing microcatheters or microwires to lurch forward. This is especially problematic during aneurysm access as the microcatheter can frequently catch at the orifice, and the release of pressure can result in a wire or catheter puncturing an already fragile aneurysm dome. If vessel perforation is suspected, often it is best to leave the devices in place and obtain a guide catheter run to assess for active extravasation. If none is observed, the interventionist may have some time to prepare additional devices to manage the perforation. Ideally, the anticoagulation effect should be reversed with protamine in the case of systemic heparinization. Hemostasis must then be assured at the site of perforation. This can be achieved with a balloon or embolic materials. If the perforation happens during coiling or liquid embolic administration, the embolization procedure is continued within the subarachnoid space as the catheter is withdrawn into the aneurysm, thus plugging the perforation. Balloons may also be useful for controlling flow at the site of the perforation. If necessary, a second access site is obtained, and the balloon microsystem is advanced to the site of the perforation. The balloon is inflated, and the perforating device is withdrawn under conditions of flow stasis. Inflation is maintained for 3 minutes at a time, with flow restored and confirmatory runs obtained to assess for further bleeding. This is repeated until no further extravasation is seen.

  
  
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  Distal thromboembolism ( Fig. 40.3, Video 40.3 ): Emboli may result from numerous procedural issues, and the management approach differs with each. Injected emboli include air and clot, both of which may occur with improper flush technique. For cerebral angiography, the double-flush technique or the use of heparinized saline pressure bags is essential to keep catheters clear. Emboli can also result from catheter manipulation of calcified vessels, causing calcific fragments to shower the distal vasculature. For patients in whom there is known or suspected calcification, particularly in the aortic arch, care should be taken to choose an access route that minimizes vessel manipulation in terms of introducing devices and minimizes the number of times the arch is traversed by selecting vessels in order as they branch off the aorta. Most distal emboli are asymptomatic, apparent only with findings of restricted diffusion on postprocedural magnetic resonance imaging. However, if a patient becomes acutely symptomatic or flow limitation is noted during the course of an angiogram, mechanical thrombectomy or intra-arterial thrombolytic infusion may be warranted.

Complications at Closure

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  Failure of closure device: Failure of closure devices is frequently noted in the acute phase, manifesting as arterial bleeding or the formation of a rapidly expanding hematoma at the access site. It may also manifest in a delayed fashion as a retroperitoneal hematoma or a groin hematoma. Regardless of presentation, manual compression at the puncture site is applied. Clamp-type pressure devices may be useful in such settings and pressure is typically applied for 20–30 minutes, although longer time frames may be prudent in cases of anticoagulant administration and/or access with a large-gauge needle.

  
  
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  Access site thrombosis or distal thromboembolism: Thrombosis at the puncture site may occur when the vessel caliber does not permit forward flow of blood around the arterial sheath. For this reason, it is essential to document distal pulses prior to access so any change in pulse can prompt further investigation. Thrombosis at the access site or distally is usually best managed by a vascular surgeon, so asking for help (a vascular surgery consultation) early is essential. If the interventionist suspects access site issues at the time of access, it may be prudent to ask for a consultation while the procedure is ongoing in case salvage maneuvers are possible while the sheath is in place.

Complications of Mechanical Thrombectomy

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  Vessel dissection with a stent retriever: Intimal damage with stent retriever use is a relatively rare occurrence and can result in flow limitation or hemorrhage. After each stent retrieval, signs of dissection should be assessed. A non-flow-limiting dissection may not require any further intervention, but antiplatelet medication may be indicated to prevent further thrombosis as a result of an exposed vessel wall. However, in the event of a flow-limiting dissection, the focus of the case must shift to stenting the dissected segment open. If no hemorrhage is noted, antiplatelet medication is instituted, and the interventionist introduces an appropriate microsystem. The dissection must be successfully crossed with a clear connection from true lumen to true lumen, as evidenced by intravascular opacification seen on a distal microcatheter injection. The stent is then advanced and deployed across the site of injury. Often, this can be successfully accomplished, along with intravenous administration of glycoprotein (GP) IIb/IIIa inhibitors, which can then be converted to dual antiplatelet medications after the acute phase of the intervention. Care should be taken to avoid unnecessary angioplasty in a dissected vessel out of concern for rupturing the already weakened vessel wall. If hemorrhage is noted, balloon tamponade proceeded by stenting is a reasonable approach. In cases where thrombolytics have been administered, vessel sacrifice may be necessary.

  
  
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  Distal thromboembolism ( Fig. 40.3, Video 40.3 ) With manipulation and restoration of flow, clots may fragment and migrate to more distal locations. Depending on their locations, it may be advisable to pursue these clots, for instance when an internal carotid artery terminus clot migrates to an M1 or M2 location. However, the relative risks and benefits of additional clot retrieval need to be assessed throughout the procedure because very distal lesions may present a risk of perforation or perforator avulsion that is greater than the risk of stroke. Frequently, after the conversion of a large-vessel occlusion to a small-vessel occlusion, patients clinically improve, despite distal thromboembolism. If the decision is reached to pursue distal emboli, we favor judicious use of stent retrievers and prefer an aspiration-only technique to avoid avulsion-type injuries.

  
  
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  Vasospasm: Vessel manipulation may result in vessel reactivity. This can limit flow, thus increasing thrombotic risks but may also make navigation of vessels more fraught. If vasospasm is noted, calcium-channel blockers can help to relax the vessel. This medication should be given time to take effect before proceeding with the intervention to avoid further vessel injury.

  
  
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  Device detachment or misplacement: Despite rigorous regulatory oversight, device malfunctions, such as inadvertent disconnection of stent retrievers, may occur. Dealing with these unforeseen events requires quick judgment. Although it is sometimes possible to retrieve stents by withdrawing them with oversized stent retrievers deployed within the stent or snares to grasp them from outside, these are difficult maneuvers that may cause further vessel injury. If the device is in a large vessel and obstructing flow, reasonable attempts should be made to retrieve. However, in cases where devices are deployed in smaller vessels or they are not flow-limiting, it is reasonable to leave them in place and to institute GP IIb/IIIa therapy and thereafter convert to dual antiplatelet therapy.

  
  
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  Symptomatic intracerebral hemorrhage ( Fig. 40.2, Video 40.2 ): Vessel perforation and reperfusion hemorrhage may both result in symptomatic hemorrhage. If extravasation is noted at the time of the procedure, it should be controlled with balloon tamponade or vessel sacrifice, as previously described. The severity of symptoms and size of the hematoma will guide further management. Small hemorrhages associated with modest symptomatology may best be managed with administration of hypertonic solutions, whereas larger lesions may require surgical evacuation. Early intervention and close surveillance are key.

  
  
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  Subarachnoid hemorrhage: Avulsion of perforating vessels because of the traction placed on vessels during mechanical thrombectomy can result in subarachnoid blood. If extravasation is noted at the time of the procedure, it should be controlled with balloon tamponade or vessel sacrifice as previously described. However, if evidence of such bleeding is only noted on postoperative CT scans, the condition can usually be managed conservatively. Serial scans are appropriate, but it is not usually necessary to treat the patient with the full subarachnoid protocol, as with aneurysmal hemorrhage.

Complications of Aneurysm Embolization (Coiling or Flow-Diversion)

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  Coil migration or loss: When a coil is deployed in an unintended location, there are a few reasonable strategies. Coil retrieval may be attempted and is often feasible with the use of a stent retriever deployed along the length of the distal coil, allowing the coil to be dragged back into the guide catheter and retrieved. Snares may also be useful for retrieval, but small vessels and difficulty grasping the coil make stent retrievers our preferred method. If retrieval does not succeed, stabilizing the coil in place with deployment of a permanent stent is the preferred option. If both methods fail, surgical retrieval must be considered.

  
  
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  Rupture of aneurysm ( Fig. 40.4, 40.5, 40.6 Video 40.4, 40.5, 40.6 ): Intraoperative rupture must be managed swiftly and in such a way that the patient does not suffer hemorrhagic and ischemic complications from the procedure. Ideally, anticoagulation should be reversed with protamine in the case of systemic heparinization. Hemostasis can be achieved with a balloon or coiling materials. If the perforation happens during coiling, the embolization is continued within the subarachnoid space as the catheter is withdrawn into the aneurysm, thus plugging the perforation. Balloons may also be useful for controlling flow. If necessary, a second access site is obtained, and the balloon microsystem is advanced to the perforation site. The balloon is inflated, and the perforating device is withdrawn under conditions of flow stasis. Inflation is maintained for 3 minutes at a time, with flow restored and confirmatory angiographic runs obtained to assess for further bleeding. This process is repeated until no further extravasation is seen.

  
  
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  Migration of flow-diversion device (distally or into the aneurysm) ( Fig. 40.7, Video 40.7 ): Flow diverter migration can be a difficult problem to manage depending on where the device lands. If migration only uncovers the neck of the aneurysm, it is usually a straightforward matter of telescoping additional devices to fully cover the aneurysm ostium. However, if device migration results in deployment within the dome of a large aneurysm, there are several management options. If the microsystem has maintained distal access, it is usually possible to use the previously described telescoping stent maneuver to span the aneurysm neck. If distal access is lost, the options depend on regaining distal access. If it is possible to get wire access across the stent, the telescoping maneuver is preferred. If not, every effort should be made to retrieve the flow diverter, usually with a snare-type device.

  
  
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  Aneurysm regrowth or rupture (late complication or failure of treatment) ( Fig. 40.8, Video 40.8 ): Coil compaction and aneurysm regrowth are known issues with endovascular treatments. Each case is individual, but options include recoiling, use of balloon or stent adjuncts for neck remnants, use of flow diverters, or surgical clip ligation.

  
  
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  Risks with dual antiplatelet therapy (if a stent is used): The current generation of intraluminal devices typically requires 6–12 months of dual antiplatelet administration to prevent intraluminal thrombus from forming as the stent heals into place. However, in neurologically impaired or elderly patients, this may cause any number of medical complications, ranging from epistaxis to severe gastrointestinal bleeds to subdural hematomas. A thorough risk-benefit discussion should be had with patients and their care providers before stopping these medications early. Usually, antiplatelet agents are only withdrawn early in life-threatening circumstances, and if possible, a single agent, usually aspirin, should be continued.

Complications of Arteriovenous Malformation (AVM) Embolization

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  Rupture of AVM: Premature embolization of arterial or venous channels with a change in flow dynamics may result in periprocedural rupture of AVMs. The critical decision in such cases is whether further embolization would stop the bleeding. In cases where bleeding is from a single vessel that could be occluded as a result of the embolization already performed, it may make sense to continue to embolize. If rupture is the result of the draining vein occluding, it is often not possible to control bleeding from a single pedicle. We favor placement of a ventriculostomy and surgical resection in most cases.

  
  
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  Proximal reflux of embolic material: Careful attention must be paid to reflux as it may occlude vessels feeding eloquent regions of the brain and cause symptomatic strokes. It is often useful to define how much reflux will be tolerated during a procedure and to agree to abort the embolization procedure if that limit is exceeded. When reflux is noted, forward pressure on the injection syringe is simply stopped. Usually this is sufficient to arrest the flow of embolic material. It is not necessary to immediately withdraw the microcatheter because frequently a modest amount of reflux can create a plug that allows for successful subsequent embolization.

  
  
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  Glue embolization in normal vasculature or the parent vessel: If glue is moving into unintended areas, it is best to immediately stop the embolization process to assess the consequences. Awake patients can be queried to determine the functional impact of the unintended embolization. If neurologic deficits are noted, mechanical thrombectomy may be attempted with stent retrievers and suction devices, as would be done for an occlusive stroke. Densely embolized vessels may not respond to these techniques, but subocclusive embolic material may be retrieved.

  
  
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  Cementing (gluing) of the distal catheter tip ( Fig. 40.9, Video 40.9 ): Aggressive embolization and reflux of glue around the catheter can make catheter withdrawal quite difficult. Although the use of detachable tip catheters mitigates this issue, it is important to have strategies to deal with stuck catheters. Most catheters will yield to persistent pressure. It can be useful to place a clamp on the microcatheter to hold constant pressure, pulling and reclamping every few minutes until the catheter releases. This can sometimes take up to 1 hour. If the catheter does not release after application of pressure, it may be necessary to cut the microcatheter at the groin. The microcatheter is stretched as much as possible and cut flush with the skin so that it recoils into the soft tissues. Pressure is held to obtain hemostasis, and the patient is placed on antiplatelet agents while the remaining portion of the microcatheter endothelializes into the vessel.

Complications of Carotid Artery Stenting

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  Plaque rupture and thromboembolic complications: Embolic protection is an essential part of carotid stenting, but there are certain cases where it fails or is infeasible. Ruptured plaque containing embolic material may lodge in distal filters or in the intracranial vasculature. If within the filter, a suction catheter can be introduced and used to clear the filter prior to retrieval. If the material is noted intracranially, the case becomes a typical mechanical thrombectomy case, with the difference being that stent retrievers may not be withdrawn through the carotid stent unprotected, meaning that they must be completely sheathed within the suction catheter or the guide catheter tip must be advanced beyond the stent to avoid entanglement of the devices.

  
  
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  Hemodynamic instability: This frequently occurs with angioplasty at the carotid bulb. Prophylactic administration of glycopyrrolate may be used to minimize this risk. If the patient becomes bradycardic or symptomatic during the procedure, the balloon should be deflated. In some patients, it may be necessary to perform several brief balloon inflations to adequately open the vessel without overly stressing the heart.

  
  
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  Hyperperfusion hemorrhage: Aggressive blood pressure management at the time of carotid stenting is essential to prevent a state of hyperperfusion. Cerebral vessels may be maximally dilated and have lost autoregulatory control as a result of chronic ischemia. Sudden reperfusion at high blood pressures can result in cerebral dysfunction or vessel rupture. Once the carotid lesion has been opened, we favor the use of nicardipine to keep the systolic pressure below 140 mmHg to minimize this risk.

  
  
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  Myocardial infarction: Routine electrocardiography and troponin blood testing every 8 hours overnight postprocedure is useful for detecting cardiac issues and preventing more severe consequences. If abnormalities arise, a cardiologist is consulted swiftly.

  
  
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  Other extracranial vessel stenting complications include dissection, occlusion, and stent migration ( Fig. 40.10, 40.11, Video 40.10, 40.11 ).

Complications of Intracranial Angioplasty and Stenting

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  Vessel rupture or hemorrhage: same as above.

  
  
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  Vessel dissection: same as above.

  
  
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  Thromboembolism: same as above.