Complications of Endovascular Aneurysm Repair

Evidence for Endovascular Repair

Two randomized European trials comparing EVAR to open surgery (OS) and 1 randomized trial comparing EVAR to no intervention were published in 2005.The first was the Dutch Randomized Endovascular Aneurysm Management (DREAM) trial, randomizing 351 patients with asymptomatic AAAs >5 cm in diameter with suitable stent graft anatomy to OS or EVAR. This study suggested a 30-day benefit in mortality favoring EVAR (1.2% EVAR versus 4.6% OS; P=0.10).The trend toward an early mortality advantage was lost, however, 12 months into the 2-year study follow-up.

The second trial, from the United Kingdom, labeled EVAR trial 1 (EVAR 1) was similar to DREAM in comparing EVAR to OS in patients with suitable stent graft anatomy and aneurysm size 5.5 cm.28 This study randomized a large group of patients (1082), with 94% receiving their allocated treatment. EVAR 1 more clearly demonstrated an early perioperative mortality benefit for EVAR (1.7% EVAR versus 4.7% OS; P=0.009).31 Blood product use and length of hospital stay also favored EVAR. In contrast, the primary end point of all-cause mortality did not show a lasting benefit for EVAR at the 4-year study conclusion, although aneurysm-related death was decreased (3.5% EVAR versus 6.3% OS; P=0.02). Complication rates (17.6 per 100 person-years EVAR versus 3.3 per 100 person-years OS; P<0.0001) and reintervention rates (6.9 per 100 person-years EVAR versus 2.4 per 100 person-years OS; P<0.0001) were much higher for stent graft repair than for open repair.

EVAR trial 2 (EVAR 2) randomized 338 patients >60 years of age with aneurysms 5.5 cm who were deemed unfit for open surgical repair to EVAR or no intervention. Between the 2 arms of the study, 142 patients died during follow-up, which correlated to a 64% overall mortality by Kaplan–Meier estimates at 4 years. This study was complicated by long delays in EVAR after randomization and a 27% patient crossover rate from the no intervention group. In the final analysis, no benefit to EVAR over medical management was detected in either overall mortality or aneurysm-related mortality for patients unfit for open surgery.

Ongoing in the United States is the Open Versus Endovascular Repair (OVER) trial, a 9-year study that began in 2002 comparing endovascular aneurysm repair with standard open surgery using a multicenter randomized trial through the Department of Veteran Affairs (VA) Cooperative Study Group.

Clinical Use

The FDA approved the transluminal stent graft treatment of abdominal aortic aneurysms in 1999. Whereas 2 devices were initially approved, AneuRx by Medtronic (Minneapolis, Minn) and Ancure by Endovascular Technologies Inc (EVT; Menlo Park, Calif), the Ancure device was removed from the market in 2001 after the company failed to submit >2500 medical device reports to the FDA. Three additional devices now also hold FDA approval, including the Zenith (Cook Inc, Bloomington, Ind), Excluder (W.L. Gore and Associates, Flagstaff, Ariz), and Powerlink (Endologix Inc, Irvine, Calif) systems. Multiple other stent grafts bearing the CE (Conformité Européenne) mark are employed in Europe after demonstrating safety for their intended use. Many stent grafts have undergone modification, with resulting technologies in the third generation and beyond. Despite the diversity among the devices, a generalized discussion of device implantation is indicated.

Preprocedural planning is the most critical component of a technically successful endovascular abdominal aortic aneurysm repair. CT provides the backbone for evaluating patient candidacy. In addition to the indications of either an asymptomatic aneurysm of appropriate maximal diameter, or a small aneurysm with features putting it at increased risk of rupture, patients being considered for EVAR must fulfill several anatomic criteria. These include -

•  lliofemoral access vessels that will allow safe insertion and deployment of the device, adequate seal, and sufficient length to provide axial support for the graft
• An infrarenal aortic neck of adequate length, limited angulation, and appropriate diameter. These anatomic features, as well as the presence or absence of thrombus and calcium at each level, can be evaluated using CT.

Complications of Endovascular Aneurysm Repair

The numbers of adverse events possible with EVAR are many, because it is a technically complex procedure typically performed on a high-risk patient population. One of the most common adverse events is the need for a secondary intervention of some type. Data from the EUROpean collaborators on Stent/graft Techniques for aortic Aneurysm Repair (EUROSTAR) registry of 2846 patients treated from December 1999 until December 2004 revealed that EVAR resulted in a cumulative incidence of secondary interventions of 6.0%, 8.7%, 12%, and 14% at 1, 2, 3, and 4 years, respectively. Secondary interventions are typically performed when the aneurysm sac has become repressurized because of incomplete exclusion of blood flow from the sac. The term “endoleak” was created to describe this complication in 1996, and a classification scheme has been adopted.Type I and type III endoleaks are treated with immediate intervention to halt perigraft flow or flow between modular components. Type II endoleaks are typically managed expectantly with intervention reserved for persistent endoleaks in the presence of aneurysm sac enlargement. The presence of a persistent type II endoleak for 6 months, however, has been associated with aneurysm enlargement, increased rate of secondary interventions, and even aneurysm rupture. Type IV endoleaks rarely occur with modern stent graft design, and type V endoleaks (endotension), although still reported, are much less frequent after modification of the Gore Excluder device in 2004 to a low-permeability expanded polytetrafluoroethylene layer. Secondary interventions occur in a spectrum ranging from diagnostic angiography to endograft removal with conversion to open repair, although the majority are percutaneous treatment of type II endoleaks with source embolization.
A related cause of endoleak and potential complication of EVAR is device failure. The integrity of stent graft materials and maintenance of proper positioning within the aneurysm are critical in preventing pressurization of the aneurysm sac and rupture. Material failure includes fracture of any of the metallic components of the stent graft, including stents, hooks, or barbs, or tears in the fabric component of the stent graft. Loss of proper stent graft position can occur for many reasons. Material failure, inadequate proximal or distal seal zone, aneurysm remodeling after EVAR, or features of the vessel, such as thrombus or calcium, that limit stent purchase, have all been implicated in the migration of stent grafts. Each of these modes of failure needs to be analyzed within the context of their clinical significance. A stent fracture that leaves the graft fabric intact and is not in a critical region for maintaining fixation would likely need only follow-up, whereas modular component separation resulting in a large type III endoleak will require urgent intervention to restore stent graft integrity.

Approach to the Small Abdominal Aortic Aneurysm

Whereas randomized clinical trials have focused on establishing the proper use of EVAR for larger aneurysms, its application for the treatment of small aneurysms is still an area of controversy. Early open aneurysm repair for aneurysms <5.5 cm in diameter does not confer a long-term survival advantage. However, retrospective analysis of the large EUROSTAR database revealed that EVAR for aneurysms with diameters between 4.0 cm and 5.4 cm had lower incidence of type I endoleak and improved cumulative freedom from aneurysm-related death relative to 2 comparison groups with aneurysm diameters of 5.5 to 6.4 cm and 6.5 cm. Level 1 evidence is lacking at this time, but the Positive Impact of EndoVascular Options for Treating Aneurysms EarLy (PIVOTAL) and Comparison of surveillance versus Aortic Endografting for Small Aneurysm Repair (CAESAR) trials were initiated in an attempt to provide such evidence. Both are device specific, randomize patients with smaller aneurysms to EVAR or surveillance, and use an FDA-approved Medtronic device or the Cook Zenith device, respectively. Until the results of these trials are published, the optimal management of small aneurysms remains ambiguous and a patient-specific approach that takes into account aneurysm morphology, biology, and patient comorbidities should be used.

Published Clinical Guidelines

The 2005 American College of Cardiology/American Heart Association practice guidelines for the management of patients with peripheral arterial disease (lower extremity, renal, mesenteric, and abdominal aortic) states that it is reasonable to offer EVAR of infrarenal aortic and/or common iliac aneurysms in patients at high risk of complications from open operations because of cardiopulmonary or other associated diseases and that repair may be considered in patients at low or average surgical risk. Whereas this document proposes a treatment algorithm setting the threshold for surgical repair at 5.5 cm except in cases of rapid expansion, it also states, “Ultimately, once an infrarenal aortic aneurysm reaches an appropriate size for graft replacement, a choice must be made between a traditional open operation or endovascular repair. Like all other aspects of aneurysm management, this decision requires a balanced judgment of relative risks.” Other features, such as saccular aneurysm morphology, patient gender, heredity, uncontrolled hypertension, and chronic obstructive pulmonary disease may also be important considerations.

 Conclusions

The patient described in the vignette meets all the recommended criteria for aneurysm repair. His age, ethnic background, and heavy smoking history are typical of patients with this disease process. The absolute aneurysm size and history of rapid expansion suggest that repair would offer a mortality benefit. Before offering EVAR, however, anatomic suitability must be confirmed by an experienced clinician using accurate imaging. Once it is established that the patient is an appropriate candidate for endovascular repair, the risks and benefits of both open and endovascular approaches should be discussed. Given the advanced age and pulmonary morbidity of this patient, endovascular repair would be appropriate therapy.

Endovascular Abdominal Aortic Aneurysm Repair

Introduction

The early 1990s ushered in the era of endovascular aneurysm repair (EVAR). Diffusion of this technology, although widespread, has been met with enthusiasm by some and caution by others. Advocates of traditional open surgical techniques maintain that EVAR is costly and that long-term outcomes for patients are inferior. The objectives of the present review are to use a case scenario to highlight the clinical problem, examine current data on the use of EVAR, and to describe the principles behind the safe application of this therapy to patients.

Case Scenario

A 78-year–old white man involved in a motor vehicle crash is evaluated in the emergency department and is found to be without serious injury. Computerized tomography (CT) reveals the incidental finding of a 4.8-cm infrarenal abdominal aortic aneurysm. He has been unaware of the aneurysm but recalls an older brother who had undergone repair of an aneurysm previously. He smokes 2 packs of cigarettes daily, has moderate chronic obstructive pulmonary disease, and has hypertension that is well controlled on a β-Blocker. He is referred to a vascular surgeon, who recommends ultrasound surveillance with a 6-month follow-up visit. The subsequent visit reveals aneurysm growth to 5.6 cm, which is confirmed by repeat CT. The patient remains asymptomatic and endovascular aneurysm repair is offered.

Clinical Impact of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a significant health risk in older populations, representing the 14th-leading cause of death for the 60- to 85-year–old age group in the United States. Necropsy studies from Europe and the United States suggest an overall prevalence of the condition of 2% to 4% for men and 1% to 2% for women. The prevalence is greatly affected by case definition, however, with less stringent definitions of AAA in population-based screening studies demonstrating a prevalence of nearly 9% in men and 2% in women. Universally noted are the graded increase in prevalence with advancing age and the increased prevalence with male gender.

Noninvasive screening programs and a dramatic rise in the elderly population have led to an overall increased incidence of asymptomatic AAA. Despite an aggressive surgical posture toward elective repair before rupture, the incidence of ruptured AAA has also continued to increase.Annually 35 000 to 40 000 aneurysms are repaired surgically in the United States.A steady upward trend in stent graft use reflected in administrative databases implies that EVAR now represents the majority of cases.1 With Markov modeling of hospital costs ranging from $16 016 to 18 484 for open repair and $20 083 to 20 716 for EVAR, AAA represents a considerable economic burden.

Pathophysiology and Current Therapies

AAAs are conventionally defined as a 50% increase in aortic diameter compared with the normal proximal aorta. The inciting events leading to AAA formation are not well understood. Some common themes of maturing aneurysms include 

•  proteolytic degradation of aortic wall
• connective tissue 
•  transmural inflammation immune responses
•   increased biomechanical wall stresses
   
  Once AAA formation is initiated, a slow steady growth of the aneurysm until rupture is typical, although on an individual basis this growth rate may be quite variable. Larger-diameter aneurysms in particular, along with female gender, advanced age, smoking, and hypertension have been associated with rapid growth. Rapid growth has consequently been associated with increased risk of rupture, although initial aneurysm size at diagnosis has the strongest association with rupture. Open aneurysm repair, initially using homografts, has successfully been employed to prevent rupture since the 1950s. The traditional open surgical approach in the modern era is performed either via a retroperitoneal or transperitoneal exposure to obtain proximal and distal aortic control. The aneurysm is then opened, back-bleeding branch arteries are ligated, and a prosthetic graft is sutured from the normal proximal aorta to the normal distal aorta or iliac segments. Flow is then restored to the lower extremities and the aneurysm sac is closed over the newly placed synthetic graft. Although effective and durable in treating aneurysms and preventing rupture, this operation has been associated with national mean mortality rates> 4% since the 1980s.

The excessive mortality associated with open aneurysm repair and a strong trend in surgery toward minimally invasive techniques led to the concept that a covered stent graft might be delivered endoluminally, effectively sealing off the aneurysm wall from systemic pressures, preventing aneurysm rupture, and decreasing associated mortality. In 1991, the first published report of stent graft implantation for AAA in humans suggested that this approach was feasible. Subsequent years have seen a tremendous surge in both the number of endovascular aneurysm repairs performed and technological improvements in stent graft design. Four Food and Drug Administration (FDA)–approved devices, each with a slightly different design, are currently being marketed . Rather than relying on sutures to provide fixation, as in open repair, endovascular stent grafts rely on radial forces of self-expanding stents for fixation or self expand in concert with active fixation using hooks or barbs at the proximal aorta fixation site. One FDA-approved device uses bare-wire suprarenal support, as well. With appropriate positioning and adequate fixation, each of these devices redirects the transmission of aortic pulsatile flow and shear forces from the wall of the aneurysm sac to the graft itself. The responses of aneurysm sacs to these changes are variable. The great majority will cease growth or shrink over time. With longer follow-up now being achieved after EVAR, >97% 5-year and >94% 9-year rupture-free survival has been observed.

Endovascular Treatment of Peripheral Aneurysms of the Posterior Inferior Cerebellar Artery

Background And  Purpose:

Peripheral aneurysms of the posterior inferior cerebellar artery (PICA) are rare, and pre-existing literature concerning their endovascular treatment is limited. The purpose of this study was to assess the etiology and clinical characteristics of peripheral PICA aneurysms and to evaluate the angiographic and clinical results of the patients who underwent endovascular treatment for a peripheral PICA aneurysm in a single center.

Material And  Methods:

 Twelve consecutive patients with 12 peripheral PICA aneurysms (10 ruptured) included in an internal data base were retrospectively reviewed. Posttreatment and follow-up angiograms were analyzed, and the clinical outcome was recorded.

Results:

The etiology was dissection in 7 (58%) and unknown in 5 cases (42%). Three dissecting aneurysms reruptured before endovascular treatment, and another 3 demonstrated angiographic progress. Four aneurysms were treated by endosaccular coiling, 6 (all dissecting) by parent artery occlusion, and in 2 cases endovascular treatment failed. Angiographic outcome was complete aneurysm and/or parent artery occlusion in 9 cases and neck remnant in 1 case. One aneurysm needed retreatment at follow-up. One lethal procedural complication occurred, and transient ischemic symptoms appeared in 2 patients. The clinical outcome was good in 7 patients, whereas 3 patients, all poor clinical grade, died (1 for unrelated reasons). No rebleedings have occurred during the follow-up.

Conclusion:

In this series, most peripheral PICA aneurysms were secondary to arterial dissection. They were unstable with a high risk of rebleeding and a high mortality if not treated without delay. Endovascular treatment was effective in preventing rehemorrhage.

after endovascular stent grafting?

What can I expect after endovascular stent grafting?

Usually you will spend 2 to 3 days in the hospital. During the first recovery day you will be permitted to eat and encouraged to walk. After you leave the hospital, you should not drive until your physician approves. You may be permitted to sponge bathe around your incisions but you should avoid soaking your groin incisions until they have healed. You may also be advised to avoid lifting more than about 5 to 10 pounds for approximately 4 to 6 weeks after the procedure.

Your physician will instruct you to return for a follow-up visit after about 7 to 10 days. At that visit, your physician will check your incisions and assess your overall condition. Usually you will undergo follow-up imaging tests 1 and 6 months after the procedure to ensure that the stent is still functioning without significant problems and in the proper location. After the first year, you will probably undergo yearly imaging tests if your aneurysm is shrinking and no problems are found. You may require more frequent imaging tests if potential problems require closer monitoring. 

Are there any complications?

The potential complications of endovascular stent grafting include:

• Leaking of blood around the graft (“endoleaks”)
• Infection
• Movement of the graft away from the desired location (“migration”)
• Graft fracturing
• Blockage of the blood flow through the graft
  Sometimes fever and an increase in white blood cell count can happen shortly after endovascular stent grafting. These symptoms usually last 2 to 10 days and are treated with medications such as aspirin and ibuprofen. Other complications that are rare but serious include a burst artery, injury to your kidney, paralysis, blocked blood flow to your abdomen or lower body, and delayed rupture of AAA.

Endovascular stent grafts can sometimes leak blood through the areas where the graft components join together, or they can allow blood to leak back into the aneurysm sac through small arteries feeding the aneurysm sac. These leaks are called “endoleaks”. Some of the leaks stop by themselves and are not dangerous, but others need to be treated immediately. These leaks can even occur years after your procedure and can be dangerous if the aneurysm continues to enlarge. Thus, after endovascular aneurysm repair, physicians require their patients to undergo long term surveillance with periodic CT scans for the rest of their life to detect and treat problems before they become threatening. Since problems with the graft or endoleaks can occur even years after successful placement, it is important to comply with the follow-up regimen advised by your vascular surgeon.

If you suspect or experience any complications because of the endovascular stent graft as described above, you should contact your physician immediately.

Endovascular Stent Graft

What is an endovascular stent graft?

An endovascular stent graft is a tube composed of fabric supported by a metal mesh called a stent.  It can be used for a variety of conditions involving the blood vessels, but most commonly is used to reinforce a weak spot in an artery called an aneurysm. Over time, blood pressure and other factors can cause this weak area to bulge like a balloon and it can eventually enlarge and rupture. The stent graft is designed to seal tightly with your artery above and below the aneurysm. The graft is stronger than the weakened artery and it allows your blood to pass through it without pushing on the bulge. Physicians typically use endovascular stent grafting to treat abdominal aortic aneurysms (AAAs), but they also use it to treat thoracic aortic aneurysms (TAAs) and less commonly, aneurysms in other locations.

Aneurysms often affect the aorta, your body’s largest artery. Your aorta carries blood away from the heart and it runs from your heart through your chest and abdomen. The normal diameter of the aorta in the abdomen is about 2 centimeters, which is a little less than 1 inch. An aneurysm is considered to have formed if the aorta grows to more than 1½ to 2 times its normal diameter.

Aortic aneurysms are potentially serious health problems since a burst aorta results in massive internal bleeding that can be fatal unless treated rapidly by an experienced emergency medical team. Endovascular stent graft repair is designed to help prevent an aneurysm from bursting. The term “endovascular” means “inside blood vessels.” To perform endovascular procedures, vascular surgeons use special technologies and instruments. These procedures require only a small incision or puncture in an artery or vein. Through these punctures, a vascular surgeon inserts long thin tubes, called catheters, which carry the devices through your blood vessels to the location of the aneurysm where they can be placed to reline and strengthen your artery. Generally, endovascular treatments allow you to leave the hospital sooner and recover more quickly, with less pain and a lower risk of complications, and sometimes a lower risk of death, than traditional surgery because the incisions are smaller. Sometimes traditional surgery is required, however, if the shape or the location of the aneurysm is not favorable for an endovascular treatment.  Your vascular surgeon will help you decide what procedure is best for your particular situation.

How do I prepare?

Your physician will ask you about your medical history and perform a complete physical examination. In addition, your physician may perform several tests, including an electrocardiogram (ECG), which measures your heart’s electrical activity, stress testing, which will help to determine your heart health and a scan to determine if your aneurysm has a favorable shape for endovascular stent graft treatment. If your physician believes that you are a good candidate for endovascular stent grafting, he or she may order one or more of the following tests. These tests show detailed images of your arteries and help your physician choose the correct size and shape of the graft

Spiral computed tomography (CT) scan: This test involves a rapid series of x rays taken in a spiral pattern around your body. A computer transforms the x ray data into three-dimensional images of your blood vessels.
Angiography: In these tests, your physician inserts a catheter into one of your arteries. Your physician then injects a dye called contrast through the catheter and takes x rays.

Am I eligible for endovascular stent grafting?

You may be eligible for elective (non-emergency) endovascular stent grafting if your aortic aneurysm has not ruptured, is large enough (5 centimeters, about 2 inches, wide or more), and you have a long enough area of normal artery for the stent graft to attach securely.  Endovascular stent grafting may be a good option if your risk for conventional surgical aneurysm repair is increased because of other illnesses you might have.  However, if you have a long life expectancy or have a low risk for complications, or if the shape of the aneurysm is not favorable for an endovascular stent graft, your physician may recommend conventional surgical aneurysm repair instead. To date, this treatment has been used for a longer period of time than endovascular stent grafting and there is general agreement that it requires less long-term maintenance than endovascular repair.

The physical characteristics of your aneurysm help your physician determine if you are a good candidate for endovascular treatment. For example, if you have an AAA located in the section of the aorta just below your kidney arteries, and there is enough space for the stent graft to seal properly, and your aorta is not severely angled, you may be eligible. Your blood vessels also must be large enough to allow the endovascular stent graft to pass through, and the device must fit the shape and contour of your blood vessels once it is in place.

Am I at risk for complications?

If you have kidney disease called chronic renal insufficiency, your chances of complications from endovascular stent grafting may be increased since contrast dye, which can affect the kidneys, is required. If you have an unfavorable aneurysm shape, associated arterial occlusive disease, or have already had an AAA repaired, you also may be at increased risk for complications. Other conditions, such as heart or lung disease, may also increase the risk for treatment.  Some of these issues may be addressed by adjunctive measures to lessen the risk of the endovascular procedure if your risk for conventional (open) aneurysm repair is prohibitive.  Your vascular surgeon will advise you regarding the best option for your particular situation. 

What happens during endovascular stent grafting?

As the procedure begins, you will usually receive a sedative and a regional anesthesia, or you might receive general anesthesia depending upon your particular circumstance. Your vascular surgery team will clean your skin and shave hair around the insertion points to help decrease your chances of infection. Your vascular surgeon will then cut into the skin overlying the femoral artery in your groin. Your vascular surgeon then threads a guide wire into your femoral artery and advances it to the aneurysm. Because you have no nerve endings inside your arteries, you will not feel the wires or catheters as they move through your body. You may feel a slight pressure or a sensation of mild tugging during this insertion.

Using x-rays that appear as moving images on a screen, your vascular surgeon inserts a catheter over the guide wire. Usually your vascular surgeon will perform angiography through the catheter to insure correct placement of the endovascular stent graft.  You may feel a warm sensation as the contrast dye is injected.  Then, a compressed form of the graft is inserted through a larger catheter, called a sheath, and the guide wire carries so it can move through your blood vessels. When the graft has reached the aneurysm site, your physician withdraws the sheath, leaving the graft in place. The graft expands to fit snugly against the walls of your artery. Often additional components of the graft are placed in a similar fashion through incisions in each groin to extend to the arteries supplying each leg.

Endovascular surgery

Endovascular surgery is a form of minimally invasive surgery that was designed to access many regions of the body via major blood vessels.Endovascular techniques were originally designed for diagnostic purposes. Basic techniques involve the introduction of a catheter percutaneously or through the skin, into a large blood vessel. Typically the blood vessel chosen is the femoral artery or vein found near the groin. Access to the femoral artery for example, is required for coronary, carotid, and cerebral angiographic procedures. The catheter is injected with a radio-opaque dye that can be seen on live xray or flouroscopy. As the dye courses through the blood vessels, characteristic images are seen by experienced viewers and can assist in the diagnosis of diseases such as atherosclerosis, vascular trauma, or aneurysms.

In recent years, however, the development of intravascular balloons, stents and coils have allowed for new therapies as alternatives to traditional surgeries such as CABG, Carotid Endarterectomy and Aneurysm clipping. Stents and coils are composed of fine wire materials such as platinum, that can be inserted through a thin catheter and expanded into a predetermined shape once they are guided into place.

Endovascular surgery is performed by radiologists, neurosurgeons, cardiologists, and vascular surgeons. The field is rapidly growing as its minimally invasive techniques offer an immediate advantage over more traditional, yet highly invasive surgeries. However, the science of endovascular surgery and its developing techniques are so new that it is currently difficult to compare the long term outcomes and complications of these patients. Several trials are underway, including CREST, and ISAT, among others.The most common and advanced form of endovascular surgery taking place today is an EVAR. This is a new technique developed to treat aortic aneurysms.

Recommendations for the Endovascular Treatment of Intracranial Aneurysms

Introduction

Intracranial aneurysms are common, with a prevalence of 0.5% to 6% in adults, according to angiography and autopsy studies. Most intracranial aneurysms are asymptomatic and are never detected. Some are discovered incidentally in neuroimaging studies and some produce symptoms due to compression of neighboring nerves or adjacent brain tissue. Others are detected only after they have ruptured and caused subarachnoid hemorrhage, a devastating type of stroke asso-ciated with 32% to 67% case fatality and 10% to 20% long-term dependence in survivors due to brain damage.

To prevent subarachnoid hemorrhage, physicians have developed methods to treat aneurysms. For ruptured aneurysms, early treatment within 24 to 72 hours has been recommended because the risk of subsequent rupture is high, with approximately 20% risk of rerupture in the first 2 weeks after subarachnoid hemorrhage. Each additional rupture substantially increases the risk of mortality and morbidity. Treatment has also been recommended for most unruptured aneurysms, although there is uncertainty about treatment of some small aneurysms <10 mm because their risk of rupture appears low. The American Heart Association formed this special writing group to summarize the literature and create recommendations on endovascular therapy of ruptured and unruptured intracranial aneurysms. This statement is meant to extend previous statements on treatment of subarachnoid hemorrhage and on treatment of unruptured aneurysms.During the review, it became evident that any recommendations would be based primarily on expert opinion weighing evidence only from nonrandomized cohort studies and case series.

Background

In 1937, Walter Dandy reported the first successful surgical clipping of the neck of an aneurysm. Microsurgical techniques have steadily evolved since then, with development of a variety of surgical approaches and metal aneurysm clips. Repair of aneurysms in nearly all intracranial locations is possible by placing a clip made from a stable metal (including platinum, titanium, tungsten, and steel alloys) across the neck of the aneurysm, thus excluding it from the cerebral circulation.

Endovascular treatment of intracranial aneurysms was first described in the early 1970s by Fedor Serbinenko, a Russian neurosurgeon. He used a vascular catheter with a detachable latex balloon to treat aneurysms, either by depositing the balloon directly into the aneurysm lumen or by occluding the artery from which the aneurysm arose.

In 1991, Guido Guglielmi was the first to describe the technique of occluding aneurysms from an endovascular approach with electrolytic detachable platinum coils, termed Guglielmi detachable coils (GDCs). GDCs are introduced directly into the aneurysm through a microcatheter and detached from a stainless-steel microguidewire by an electrical current . The aneurysm is packed with 1 or more GDCs, thereby excluding it from the circulation .

As clinical experience with this technique has increased and coil design has improved, coil embolization has been used with increasing frequency even in patients who could be treated by conventional surgical clipping. Furthermore, some centers are treating patients with surgical clipping only if they cannot be treated primarily by endovascular coil embolization therapy. In August 2002, it was estimated that 100 000 patients with intracranial aneurysms had been treated with GDCs at sites throughout the world, with approximately 1500 patients being treated per month.

Given the wide use of endovascular coil embolization to treat intracranial aneurysms, it is important to establish recommendations, based on the best available evidence, to define appropriate indications for coil embolization and other endovascular techniques in the context of surgical alternatives. The essential elements to compare are risk of morbidity and mortality, and efficacy, measurable in terms of reduced risk of aneurysm rupture after treatment.

Procedural Risk

Intracranial aneurysm treatment, by either surgery or endovascular coiling, may precipitate a complication that could lead to new symptoms, disability, or death. In comparing procedural risks, a measure of complications caused by the treatment itself would be ideal so that the impact of the therapy could be isolated from other aspects of presentation or medical care. For example, brain injury from subarachnoid hemorrhage at presentation or from aspiration of gastric contents during airway manipulation may lengthen hospitalization or result in disability, and these complications could obscure the impact of the procedure itself on outcomes. However, determinations of what “procedure-related” means are subjective and require judgment; hence, “measurements” of procedure-related complications are unreliable. In formulating these guidelines, we have favored comparisons of functional outcomes when available in the literature.

Functional outcomes after subarachnoid hemorrhage are highly dependent on the severity of the initial hemorrhage.Although researchers have attempted to adjust for differences in pretreatment prognosis, it is not possible to ensure that adjustment is adequate to compare results in different case series. Thus, comparison of results of case series of procedural risk in ruptured aneurysm treatment should be avoided.

As with all procedures, risk is affected by patient selection, technical expertise, and supportive services, and its measurement is influenced by the definition of the outcome and the judgment of the evaluator. Descriptions of retrospective case series, which dominate the literature on procedural risk of intracranial aneurysm treatment either by surgery or by endovascular coiling, should be considered skeptically given potential sources of bias and will be reviewed only briefly. Comparative studies that include patients treated by both modalities are more likely to assess outcomes impartially and may provide more reliable comparisons of surgery and endovascular coil embolization.