Keywords
complications - neurointervention - thromboembolism
Introduction
The endovascular approach to the central nervous system began just a few decades ago
and has become a very important tool in the arsenal of neurosurgeons. This has become
one of the rapidly evolving specialties of medicine. In the early days, endovascular
procedures involved usage of crude hardwares, lengthy surgical time, and lot of complications.
Any injury to the cerebral vasculature results in catastrophic outcome with major
morbidity and mortality. Even though a lot of advancements have taken place in techniques
and technologies over the time, the specialty still remains in infancy and complications
still result in major clinical disasters.
Complications associated with neuroendovascular therapy are common and vary with the
status of the lesion being treated.[1] Overall complication rates are around 20%, with a 1-month mortality rate estimated
at 1.4%.[1]
[2] The most commonly reported complications in endovascular neurosurgery include thromboembolic
events, groin-site hematoma, contrast-induced nephropathy, intraoperative rupture,
failure to treat lesion, and radiation-induced effects.[3] We focus this review on complications common to both diagnostic and therapeutic
procedures of neurointervention, as thorough knowledge will help the endovascular
surgeon anticipate problems and thus help in avoiding them.
Complications Related to Vascular Access
Complications Related to Vascular Access
Femoral access is still the most common mode of vascular access for neuroendovascular
procedures, though in some selective cases, transradial access can be opted. The femoral
artery, in most of the population, is a larger caliber artery (permitting larger-size
catheters) and is less prone to spasm when compared with the radial artery.[4] Recognition of access site complications and early treatment of these complications
can prevent more serious complications and death. Complications include groin hematoma,
retroperitoneal hemorrhage, formation of pseudoaneurysm and arteriovenous fistula,
arterial occlusion leading to ischemic limb, femoral neuropathy, and infection. Complications
for diagnostic procedures are lower due to use of smaller-sized sheaths and shorter
duration of procedure.[5]
[6] Wagenbach et al, in their recent series of almost 300 patients who underwent diagnostic
and therapeutic neuroendovascular procedures, report a rate of 1% incidence of groin
hematoma.[7] Severe groin hematomas require surgical intervention for definitive therapy, and
if left untreated, may progress to retroperitoneal hematoma, which can be catastrophic.
Looking for peripheral pulsation (dorsalis pedis artery, posterior tibial artery in
femoral puncture) pre- and postprocedure is always recommended.
Incorrect site of the femoral artery puncture is the most common cause of these complications.
Puncturing below the femoral bifurcation is usually the reason for pseudoaneurysm
formation, groin hematoma, and arteriovenous fistulas, whereas retroperitoneal hemorrhage
(incidence of < 3%) is caused by femoral punctures above the level of inguinal ligament.[8]
[9]
[10] Early identification of bleeding and vascular complications is important as these
complications are associated with adverse events. A thorough knowledge of the surface
anatomy of femoral artery and its application along with the use of ultrasound scan
or fluoroscopy for guidance of femoral punctures can reduce these complications.[11]
[12]
[13] Furthermore, the micro puncture technique has been shown to reduce complications
but is not widely adopted.[14] Radial puncture for the vascular access is on the rise among the interventionists,
and few studies have shown that it is associated with significantly lower complications.[15] Problem with radial access is difficult navigation into the carotid system.
To reduce access-related complications, one should avoid areas of previous surgery
(such as hip replacement or hernia repair) or a lower extremity in which vascular
repair has been performed. In most centers, manual compression is given at the puncture
site to avoid groin-site hematoma and its related complications. Care should be taken
to access the femoral artery at a compressible site below the inguinal ligament ([Fig. 1]). Puncture site closure devices, including collagen plugs, percutaneous devices,
and external compression devices, have become popular recently to prevent access-related
complications[16]
[17]
[18] though concrete evidence regarding their benefits in reducing complications is still
lacking.
Fig. 1 Ideal site of femoral puncture between the femoral bifurcation and inferior border
of inferior epigastric artery.
Vasospasm and Dissection
Placing and navigating even a guiding catheter during neurointervention procedure
may cause vasospasm or, in severe cases, dissection ([Fig. 2A]). It is always better to avoid such scenario by using nimodipine infusion in flush
bags, or if it occurs, then by slowly injecting nimodipine or 50 to 100 µg nitroglycerine
through guiding catheter. In severe cases of dissection of internal carotid artery,
stent deployment remains the only resort ([Fig. 2B]).
Fig. 2 (A) Dissection with guiding catheter. (B) Stent deployment.
Thromboembolic Events
The reported incidence of hyperacute thromboembolic complications is seen to vary
between 3 and 11% in previous series.[19]
[20]
[21] Incidence depends on rupture status of the treatment target, mode of detection of
the event, and type of procedure performed.[22]
[23] Carotid artery stenting has got higher intraprocedural thromboembolic rates, with
significantly higher risk in patients with symptomatic lesions. Iatrogenic dissection,
catheter-induced vasospasm, and operative technique account for most of these events.
Patients older than 60 years, those with cerebrovascular disease, and those with longer
procedure times are also at greater risk.[24] Thromboembolic complications induce perioperative morbidity. Therefore, avoiding
thrombus formation during endovascular treatment is important. Though reported thromboembolic
episodes are high, persistent neurologic deficits occurred only in 2 to 5% of the
patients.[21] In one study, stroke rates at 30 days after the procedure is around 5%.[22]
In current practice, many strategies are used for prevention of thromboembolic events.
A carefully titrated systemic heparin therapy to keep activated clotting time (ACT)
between 250 and 300 with varying treatment duration before, during, and after the
procedure is the most commonly used strategy. Aspirin and clopidogrel are routinely
used for thromboembolism prophylaxis in patients undergoing stent placement.[25] Although the combination helps in preventing thrombotic complications in stent placement,
some patients do not respond to clopidogrel and have a higher risk of stent thrombosis.
Sedat et al studied the efficacy of prasugrel, another platelet inhibitor and an irreversible
antagonist of P2Y12 ADP receptors, and found that it reduces the clinical consequences of thromboembolic
complications of endovascular treatment with stenting and coiling of unruptured intracranial
aneurysms.[26] Ticagrelor is a new reversible ADP P2Y12 platelet receptor inhibitor with no known
resistance that will be help in clopidogrel-resistant patients. Yamada et al,[27] in a study of 369 consecutive aneurysm coil embolization cases, retrospectively
noted that patients who had been treated preprocedurally with clopidogrel and/or aspirin
had significantly fewer thrombotic complications than those who received antiplatelet
therapy only postprocedurally or those who received no antiplatelet therapy (1.9%
vs. 2.3%, and 16%, respectively). However, in ruptured aneurysms, benefits of antiplatelets
has to be carefully weighed against the risk of hemorrhagic complications related
to other procedures, such as ventriculostomies, and devastating consequences of intraprocedural
rupture (IPR) or rerupture of the aneurysm prior to its complete repair.
A variety of rescue therapies have recently been applied when embolism occurs. Intraprocedural
administration of abciximab and other glycoprotein IIb-IIIa inhibitor were used in
small uncontrolled series with some good effect. Treatment with another glycoprotein
IIb-IIIa inhibitor, tirofiban and eptifibatide, has also been reported in uncontrolled
series to be safe and effective for dissolving intraprocedural clots[28]
[29] ([Fig. 3A, B]). Ries et al analyzed the effect of a modified intraoperative anticoagulation strategy
including intravenous acetylsalicylic acid (ASA) (not available in India) on complication
rates during endovascular coil embolization. They found that intravenous ASA was associated
with a significant reduction in the rate of thromboembolic events without increase
in the rate or severity of intraoperative bleedings.[30] In few instances where complete occlusion occurs, stent retrievers will help in
restoration of the flow ([Fig. 4A–D]).
Fig. 3 (A) Post coiling thrombus formation in callosomarginal artery. (B) Same patent after infusion of G IIb-IIIa inhibitor.
Fig. 4 (A) Complete occlusion of right A1 post Acom aneurysm coiling. (B) Microcatheter placement beyond occlusion site. (C) Placement of stent retriever. (D) Complete reperfusion post clot retriever.
Air embolism, also a feared complication ([Fig. 5]), deserves mention as there are various preventive strategies that can be used.
Making sure of an airless flush bag and line system at the beginning of the procedure
may be a useful component of endovascular safety measures to prevent air embolism.
Fig. 5 Air embolism in posterior cerebral arteries.
Contrast-Induced Complications
Contrast-Induced Complications
Contrast-induced nephropathy is a is a serious complication of angiographic procedures
resulting from the administration of contrast media with an incidence of less than
5% in low-risk patients and 20 to 30% in high-risk patients after contrast administration.[31] Risk factors include contrast-related factors such as high osmolar content, ionic
contrast agents, and high viscosity and high contrast volume. Patient-related factors
include chronic kidney disease, diabetes mellitus, older age, and other cardiovascular
risk factors. It is defined as an elevation of serum creatinine of greater than 25%
or 0.5 mg/dL or greater from baseline within 48 hours. Good hydration during the procedure
and of N-acetylcysteine or bicarbonate and use of iso-osmolar and nonionic contrast have been
proposed as nephroprotective strategies.[32]
[33]
In the presence of risk factors, alternative imaging techniques should be considered
first if the risks are thought to be outweighed by the benefits of contrast administration.
When possible, nonsteroidal anti-inflammatory drugs should be withheld for at least
24 hours before and after the procedure, and metformin should be avoided for at least
48 hours before the procedure. It should not be restarted until it is clear that contrast-induced
nephropathy has not developed after the procedure. Sodium bicarbonate and N-acetylcysteine may have beneficial effects,[34]
[35] but no conclusive evidence has been found so far.[36]
[37]
[38]
Intraprocedural Rupture
The most feared and fatal complication of endovascular surgery is the dissection of
the vessel or rupture of an aneurysm. Reports of its incidence range from 1 to 9%.[19]
[39]
[40] Patients who have IPR during coiling usually fare worse than those who experience
this complication during open surgery, as the resulting bleeding cannot be immediately
evacuated, and all efforts are aimed solely at trying to repair the leakage, potentially
even at the cost of vessel sacrifice. The CARAT (Cerebral Aneurysm Rerupture After
Treatment) study done at nine high-volume centers in the United States included 1,010
ruptured intracranial aneurysms. They compared the rupture rates in patients treated
with coiling and clipping and found a 5% risk of IPR in the coiling group with an
attendant 64% rate of death or disability compared with a 31% rate of death or disability
among patients who experienced an intraoperative rupture during open surgical clipping.[41] Risk factors for intraoperative rupture during occlusion of aneurysms include small
aneurysm size, recent rupture, and the presence of a daughter sac. Another study by
Park et al showed an incidence of IPR in 7.5% (6/80) in ruptured aneurysms and 2.5%
(4/155) in unruptured aneurysms.[42] They concluded that independent risk factors for IPR during endovascular treatment
of intracranial aneurysm were aneurysm size and anterior communicating artery aneurysm.[42] Ruptured aneurysms showed a higher tendency toward IPR than did unruptured aneurysms.
Aneurysms with a sharp angle between the parent vessel and fundus also had a higher
incidence of rupture. The aneurysm can be perforated through the dome by a guidewire
or microcatheter. An aneurysm can be entered with the microwire sheathed inside the
microcatheter, and this may reduce the risks of perforation. Distal curve in the microcatheter
and microwire may reduce the chances of impinging directly on the wall. Coils themselves
may cause rupture even if soft coils are used. This most commonly occurs during deployment
of last coil and rupture may occur either at the neck or the dome.
In the case of aneurysm rupture during procedure, the management consists of immediate
reversal of the heparin using protamine sulfate in the dose of 1 mg of protamine for
100 units of heparin, continuing with the originally planned coil embolization process
and placing coils in the subarachnoid space and in the aneurysm. This may not be successful
in some cases as the placement of coils may further increase the size of the rent
in the aneurysm. It is better to have balloon in place in case of such catastrophes,
especially during initial few cases. Placement of an emergency external ventricular
drain may help in reducing the intracranial pressure. In some cases, vessel may have
to be sacrificed.
Vessel rupture during arteriovenous malformation (AVM) embolization may occur when
perforation of a feeding or draining vessel is caused by the microwire or microcatheter.
Rescue therapy may consist of immediate injection of embolization material unless
the injury is too far upstream.[43] Improvements in access and embolic devices with proper endovascular techniques in
experienced hands all contribute to minimizing the risk of intraprocedural aneurysm
rupture.
Failure to Treat Lesion
In some patients, anatomical or technical difficulties may result in failure to achieve
targeted result. Reports of such occurrences are now rare, with latest improvement
in hardwares, but the available literature suggest an incidence of 4 to 6%.[1]
[2] Risk factors include lack of experience of the endovascular surgeon, lesion locations
that are difficult to reach, and tortuous vasculature. When an endovascular procedure
has to be abandoned, alternative methods include repeat angiography, open surgery,
or radiotherapy. Careful study of the preoperative imaging, including noninvasive
and invasive imaging of the access vessels and target lesion, is important in avoiding
such situations. The use of postprocessing of images in three-dimensional (3D) software
may help predict difficulties and thereby reduce the incidence of “failed” attempts.
In the future, preoperative simulation of the anticipated procedure may not only prevent
failed attempts but also allow preparation for the use of the specific devices most
likely to succeed in a particular anatomical setting.[44]
Hardware Failures
Older generation coils were used to stretch during coiling or sometimes detach before
being deployed ([Fig. 6]), so newer stretch resistant coils are introduced. Similarly microcatheter used
to break in between during AVM embolization ([Fig. 7]), so detachable microcatheters are available now to reduce complications. With the
advancement in technologies, such hardware-related complications are decreasing but
still they occur occasionally, and which as a neurointerventionist we have to deal
more with presence of mind rather than on some facts and literature.
Fig. 6 Early auto detachment of coil stent markers seen, which was used to hold coil in
place.
Fig. 7 Broken and recoiled microcatheter during AVM embolization. Liquid embolization agent
cast seen.
Radiation-Induced Complications
Radiation-Induced Complications
This can be divided into acute and long-term effects. Short-term effects from ionizing
radiation include skin burns that may occur from exposure to radiation doses as low
as 2 Gy, whereas hair loss may occur after 3 Gy.[45] Not only is the patient at risk for harm due to ionizing radiation exposure during
these procedures, but the treating physician is also at risk.[46] There are no prospective studies available in the literature that actually studies
the cause and effect of relation of these radiations and neoplasms. Techniques to
minimize radiation to both patients and their treating physicians include lead shielding,
collimation, and minimizing the exposure time and number of runs during angiography.
Conclusion
Endovascular neurosurgery has advanced rapidly since its inception over past few decades
with evolving techniques and hardwares, thus reducing the incidence of complications.
However, still whenever complications occur, significant morbidity and mortality are
associated. A thorough knowledge of the procedures, hardwares, proper training, and
knowledge about complication avoidance will help in reducing these adverse events.
Also, experience, knowledge, and preparedness about the complications will help in
managing these complications successfully, thus reducing morbidity.
