Introduction
When AAA ruptures are not repaired, they invariably lead to the patient’s death. In addition, ruptured aortic aneurysms (rAAA have high mortality (35–55%) and morbidity rates when treated by standard open surgical methods.1–5 These high perioperative mortality and morbidity rates have not been substantially reduced, despite the introduction of many improvements in open surgical techniques and perioperative care.1–6 The introduction of endovascular approaches to treat AAA in the early 1990s seemed like an opportunity to alter substantially treatment outcomes when rupture occurred.7,8 The present article details how these endovascular approaches, which include endovascular stent-grafts, can be applied to the treatment of rAAA, and what advantages these new catheter-based treatments afford.
Obstacles to the Use of Endovascular Grafts in the Ruptured Aneurysm Setting
The less invasive nature of endovascular treatment of rAAA offers many potential advantages. However, one obstacle in the early days of endovascular AAA treatment was the availability of an appropriate graft for each patient. To obtain such grafts, it was necessary to have complex measurements of aneurysmal and adjacent arterial lengths and diameters. These measurements are usually based on high-quality contrast computed tomographic (CT) scans and arteriography, which take time to perform and which may not be quickly available in the rAAA setting. Moreover, it may not be possible to have a suitable stock of grafts available for most patients. A second obstacle to the use of endovascular grafts was that standard surgical practice mandated early proximal aortic control, and it was thought that this could be achieved most rapidly and most effectively by laparotomy, with placement of a supraceliac or infrarenal aortic clamp.9
Suitable Endografts for Endovascular Repair in the rAAA Setting
To overcome the first obstacle, a derivative of the original Parodi endograft10 has been available since 1993 to treat aortic and aortoiliac aneurysms. This Vascular Innovation (VI) graft (originally made by us from available materials, but is now to be marketed as the VI Graft, distributed in Europe by Datascope-Maquet), which is used in an aortofemoral configuration, is comprised of a large, proximal Palmaz balloon-expandable stent affixed to a long, tulip-shaped PTFE graft.11 This graft is “a one-size-fits-most,” since the proximal diameter can vary between 20 and 27 mm, depending on the inflation pressure applied to the deployment balloon, and the excess graft length can be cut off and tailored appropriately before the distal graft is sutured to its introduction site within the common femoral artery. Having this graft sterilized and available has had the potential of eliminating the need for some preoperative measurement and fabricating, or procuring a suitable graft for use in the urgent setting of a rAAA. Moreover, as the commercially made modular endografts became available, components of these grafts were more frequently stocked in operating rooms and could be used to treat rAAA.
Early Experience with Endovascular Treatment of rAAA
On April 21, 1994, a patient presented with a rAAA with all the usual clinical sequellae, i.e., severe abdominal pain, hypotension, and a large pulsatile abdominal mass. Because he had had a total cystectomy and ileal bladder and severe symptomatic coronary artery disease (CAD) with an ejection fraction of 20%, he was deemed unsuitable for an open repair of his rAAA. However, because we had a surgeon-made graft available, we were able to perform an endovascular graft repair of his rAAA along with placement of a right common iliac artery occluder and a femorofemoral bypass.7 The patient did well following this procedure until he died from cardiac disease 3 years later. To our knowledge, this was the first endovascular graft repair of a rAAA, although another early case was reported by Yusuf et al.8 Following our experience with this first successful case, we performed similar procedures on another 11 patients with ruptured aortoiliac aneurysms.11 All these patients had major contraindications to open surgery, with serious medical comorbidities (e.g., coincident major myocardial infarction, chronic obstructive pulmonary disease [COPD requiring home oxygen therapy] or surgical problems producing a hostile abdomen (e.g., abdominal infection, intestinal stomas or massive recurrent incisional hernias). All 12 of these first patients were stable enough to undergo preoperative CT scanning to confirm the aneurysmal rupture. In all 12 of these original patients, the ruptured aneurysm was successfully excluded by the endovascular graft. Moreover, only 2 of the patients died within 2 months of the procedure, a 17% operative mortality rate.
Hypothesis Regarding Endovascular Treatment of rAAAs and Current Management Plan
This low operative mortality rate prompted us to speculate that all rAAAs should be treated endovascularly. Such an approach might lead to better outcomes than were currently being achieved with open repair. In 1995, we therefore adopted the following treatment plan:9 In the operating room, the patient was prepared for fluoroscopy from the neck to the knees. Then, via a femoral or brachial puncture under local anesthesia, a guidewire was placed in the supraceliac aorta. Using this guidewire, a catheter was placed to visualize the abdominal aorta and iliac arteries angiographically. This angiogram, which was best performed with a power injector, allowed a determination of whether an endovascular graft repair of the rAAA was possible on the basis of aortic neck and iliac artery anatomy. If not, a standard open surgical repair was performed.
Control of Bleeding and Blood Pressure: Restricted Resuscitation or Hypotensive Hemostasis and Proximal Balloon Control
As already noted, it was widely believed that with rAAA, it is necessary to perform immediate laparotomy to permit clamp control of the aorta proximal to the aneurysm. With major arterial bleeding in other circumstances, however, restricted fluid resuscitation and withholding blood transfusions have been shown to decrease blood loss and improve outcomes.13–16 One editorial in 1991 also advocated restriction of fluid resuscitation in the preoperative management of rAAA.17 We believe that strict restriction of fluid and blood resuscitation in the rAAA setting is mandatory. If the blood pressure is in the 50–70 mmHg range, it should be left there. If the patient is moving and talking, no fluids should be given. This should continue when the patient is first in the operating room being prepared for treatment and having a guidewire and catheter placed in the suprarenal aorta under local anesthesia via either a femoral or brachial puncture. Although endovascular treatment may lead to a delay in gaining aortic control, with the use of hypotensive hemostasis, such delays have not proven to be a problem. Patients with rAAA frequently deteriorate with induction of anesthesia. If that occurs and the blood pressure falls below 50 mmHg or is unobtainable, administration of fluid and blood becomes necessary. We believe such deterioration warrants proximal balloon control and have used this technique selectively in our current management plan for ruptured aneurysms.
Proximal Balloon Control
If and when patients deteriorate before, during, or after induction of anesthesia, a larger size (14–16 Fr) hemostatic sheath is inserted over the previously placed guidewire via either the femoral or brachial artery. Heparin is then given to the patient. With the wire in place, a 27-, 33-, or 40-mm compliant (latex) balloon is inserted through the sheath and inflated with dilute contrast under fluoroscopic control (Figure 4) in either the supraceliac or pararenal aorta (depending on the length of the infrarenal neck). If the femoral route is chosen for balloon placement, the sheath must be kept in place in the aorta to support the balloon and to facilitate its removal after graft placement. With the balloon inflated, the remainder of the procedure is conducted as rapidly as possible to minimize the duration of visceral and renal ischemia. If the infrarenal neck is too short, too flared, or too angulated for an endovascular repair, open aortic control, preferably below the renal arteries, is obtained and a standard AAA repair performed. If a bifurcated endograft is inserted, an infrarenal balloon should be placed within the large proximal part of the graft to replace the more proximal balloon as soon as possible. Then the endograft procedure is completed in a deliberate fashion.
Experience with Endovascular Treatment of rAAA
To date, we have treated 57 patients with rAAA using endovascular techniques. Included are the 12 original patients already described and another 45 patients treated according to our current management plan. Of these 57 patients, 12 were deemed unsuitable for endovascular treatment because of their aortic neck or iliac anatomy. These 12 underwent open repair and only 3 required inflation of the proximal balloon. All survived for more than 2 months after operation. Of the remaining 45 patients who received an endovascular graft, 35 had the graft inserted without the need for proximal balloon control. Only 10 of the 45 patients required balloon control. Twenty-five of these patients were treated with a VI graft, and 20 received an industry-made graft (AneuRx [Medtronic, Santa Rosa, California], Zenith [Cook, Bloomington, Illinois], or Excluder [W.L. Gore, Inc., Flagstaff, Arizona]). In all 45 endograft-treated patients, the graft was deployed successfully and completely excluded the ruptured aneurysm. There were no significant endoleaks, and all surviving patients became and remained asymptomatic. Seven of the 45 patients died within 30 days after their procedure, but all had serious medical comorbidities (coincident major myocardial infarctions and/or oxygen dependent COPD). Thus, in this entire series of 57 rAAA patients, there was a procedural mortality rate of only 12.3%. Two patients receiving endovascular grafts required evacuation of a large retroperitoneal hematoma for abdominal compartment syndrome. In one of these patients, the decompression was required immediately after graft placement; in the other, it was required several days later. Two groin wound infections required drainage, but healed without graft involvement.
Collected World Experience with Endovascular Graft Treatment of rAAA
Over the last 9 years, a collaborative group, the EVAR for Ruptured Aneurysm Investigators, have been pooling their results with the use of endovascular graft repair of rAAA. The results of this study will be published in November 2009. Many of the details of this experience cannot be described here. However, the highlights can be summarized. Data were collected from 44 centers on 1,037 rAAA patients who were treated by EVAR. The overall 30-day mortality in these patients was 21%, although that figure may be biased by the fact that in many centers, unstable patients who were deemed at greater risk were uniformly treated by open surgery, while EVAR was used on more stable patients. However, 13 centers were identified in which EVAR was employed to treat all anatomically suitable rAAA patients. In these 13 centers, 680 rAAA patients treated by EVAR had a 30-day mortality of 19.7%, while 763 rAAA patients treated by open repair had a 30-day mortality of 36.3%. Although the 2 patient groups may not have been perfectly comparable, this mortality difference is highly statistically significant (p Why Results of EVAR For rAAA Vary Although some groups have achieved excellent results with EVAR for rAAA and have reported a low 30-day mortality rate, ranging from 10–25%, other centers have not been able to reproduce these results. Indeed, some reports have shown no improvement when comparing EVAR to open repair in the treatment of rAAA. We believe these variable results are due to technical factors, the use of adjuncts and the strategies, which are used in the performance of the EVAR procedures themselves, and the myriad of other details, which may influence the outcome of treatment for rAAA. Key among these are the use of a protocol and organization for the treatment of rAAA, the presence of an endovascularly trained staff committed to this protocol and the optimal management of rAAA, the routine use of hypotensive hemostasis, an awareness of abdominal compartment syndrome, a willingness to detect it early and treat it aggressively, and the appropriate use with proper techniques for supraceliac aortic balloon control. All of these components of treatment, which are detailed in this article and elsewhere, are important in achieving optimal results with EVAR in the treatment of rAAA. We believe that when all these components of treatment are in place, EVAR will produce better outcomes with rAAA than open repair, as has been demonstrated in a number of centers that employ them. If these components of treatment are used, the superiority of EVAR will become apparent, and a randomized, prospective trial will not only be unnecessary, but will also be impossible to perform for ethical and logistical reasons.
Advantages of Endovascular Treatment of rAAA
Among the advantages of EVAR for rAAA is the ability to obtain proximal control without general anesthesia, the ability to deploy the graft from a remote access site, reduced blood loss, and the minimization of hypothermia by eliminating laparotomy.
Proximal Control without General Anesthesia
Patients with rAAA may be severely hypotensive. However, many patients may have their blood pressure stabilized at a nonlethal level. This is due to sympathetically mediated vasoconstriction in response to hypotension. It is not uncommon for this vasoconstriction to be released during the induction of general anesthesia, which results in a sudden drop in blood pressure. Therefore, a relatively stable patient may become severely hypotensive, mandating urgent application of a proximal aortic clamp. However, a guidewire can be inserted in the upper abdominal or lower thoracic aorta through a percutaneous puncture under local anesthesia, while maintaining vasoconstriction. Once the guidewire is inserted in the aorta, the patient can then safely undergo induction of general anesthesia because proximal control can be rapidly and relatively safely obtained by an occlusion balloon placed over the previously inserted guidewire.
Graft Deployment from a Remote Access Site
Endovascular grafts can be inserted and deployed through a remote access site, thereby obviating the need for laparotomy and, more importantly, eliminating the technical difficulties that are encountered when performing a standard repair in the rupture setting. With the associated bleeding, the anatomy of the retroperitoneal structures is often distorted and obscured by a large hematoma, which may lead to technical difficulties, as well as inadvertent injury of the inferior vena cava, the left renal vein or its genital branches, the duodenum, or other surrounding structures. These iatrogenic injuries have been the cause of significant operative morbidity and mortality following standard surgery for rAAA. In contrast, endograft repair is performed within the arterial tree, which is unaffected by extravasated blood or previous operative scarring. Thus, the technical difficulty encountered when treating a rAAA with an endograft is similar to that for elective cases. Moreover, this approach completely eliminates the risk of inadvertent injury to surrounding structures.
Reduced Blood Loss
In our experience, EVAR for rAAA was accomplished with a relatively small amount of additional blood loss compared to that which occurs during open rAAA repair. This advantage is more important in patients with rAAA because they have already lost a significant amount of blood following rupture, and coagulopathy or disseminated intravascular coagulation secondary to further blood loss can be serious and often lethal complications. There are several reasons why blood loss was limited, including the maintenance of the tamponade effect within the retroperitoneum. In addition, back-bleeding from the iliac and lumbar arteries and bleeding from the anastomotic suture lines and from iatrogenic venous injuries are eliminated.
Minimizing hypothermia. Hypothermia secondary to poor perfusion and laparotomy can exacerbate coagulopathy, which is one of the causes of mortality following open surgical repair. Endovascular graft repair can minimize the extent of hypothermia by avoiding laparotomy.
Discussion
The relatively low mortality rates in rAAA patients treated endovascularly are encouraging, particularly because many were high-risk patients who were poor surgical candidates.12,18–21 These results show that endograft repair of rAAA is feasible and effective in selected cases. However, before the universal use of these techniques is adopted, many questions must be answered. Should endovascular repair be attempted in all rAAA patients or just those who are relatively stable? In what proportion of rAAA patients should an endograft repair be used? Should a CT scan be obtained before rAAA patients are taken to the operating room or endovascular suite? In which patients should a proximal balloon be placed? How should this be done? Is a randomized, prospective comparison with open repair necessary or justified? Should an aortounilateral graft be used or a modular bifurcated graft? What kind of anesthesia should be employed? What resources are required for an institution to undertake endograft repairs of rAAA? Until these questions are answered, we will not know the optimal approach to endovascular repair of rAAA. Nevertheless, we believe that endovascular grafts represent a potentially better way to treat this entity, since previous open-surgical methods have had such a persistently high morbidity and mortality. We currently believe that these endovascular grafts can and should be used in all anatomically suitable patients and in over 50–60% of all patients who present with a rAAA. Indeed, some of the sickest, most urgent hypotensive patients may benefit the most from endograft treatment rather than subjecting them to an emergent open repair under suboptimal conditions. Moreover, we believe that the use of fluoroscopic techniques to facilitate the placement of proximal occlusion balloons for rAAA,11,12,21 an old idea,22–25 will make this endovascular adjunct a practical and valuable one, even if an endovascular graft procedure is not possible and an open repair is required. And finally, we believe that hypotensive hemostasis or restricted fluid resuscitation will prove valuable in the rAAA setting, whether treatment is by EVAR or open repair. Hypotensive hemostasis will likely become the standard of care for all rAAA leading to improved treatment outcomes for this lethal condition.
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From the *Cleveland Clinic, Cleveland, Ohio, and §New York University Medical Center, New York, New York.
Manuscript submitted September 9, 2009, provisional acceptance given September 21, 2009, accepted September 29, 2009.
Correspondence: Frank J. Veith, MD, 4455 Douglas Avenue, Bronx, NY 10471. E-mail: fjvmd@msn.com
Disclosure: This work was supported in part by grants from the William J. von Liebig Foundation.
