EVAR for Treating Ruptured AAAs
A standardized endovascular approach for treating abdominal aortic aneurysms is presented and studied.
Elective endovascular aneurysm repair (EVAR) has become an established means of treating abdominal aortic aneurysms (AAAs),1,2 and although EVAR for treating ruptured AAAs (r-AAAs) is feasible, open surgical repair of r-AAAs remains the gold standard.3-10 Unfortunately, regardless of advances in postoperative care of patients with r-AAAs, the associated morbidity and mortality rates remain high, ranging from 35% to 80%.3-10
There are several reasons for our failure to adopt the endovascular means for treating r-AAAs: (1) unavailability of preoperative CT in patients with r-AAAs; (2) unavailability of a dedicated operating room and ancillary staff equipped to perform emergent EVAR at all times; (3) unavailability of "off-the-shelf" stent grafts; and (4) the lack of data based on multicenter randomized trials. We recognized that the principal limitations of treating patients with r-AAAs was our inability to coordinate a seamless transition of patients with r-AAAs from the emergency room to the operating room and undergo endovascular repair.
Therefore, we established a protocol to train the emergency room physicians, the anesthesiologists, the operating room nurses, and the interventional radiology technicians who would be involved in treating patients with r-AAAs by simulating these emergent circumstances on patients with symptomatic AAAs. To facilitate standardization of EVAR for r-AAAs, the steps of the procedure were well rehearsed with the health care providers involved in patient care. Once a standardized protocol was established for treating r-AAAs, we utilized endovascular means as our primary modality for treating patients with aneurysm rupture.
MATERIALS AND METHODS
In 2002, we established a multidisciplinary approach for treating patients with r-AAAs, which included vascular surgeons, emergency room physicians, anesthesiologists, operating room staff, radiology technicians, the availability of a variety of stent graft sizes and types, and an operating room that was adequately equipped to perform endovascular procedures with at least an OEC-9800 mobile fluoroscopic unit (GE OEC Medical Systems, Salt Lake City, UT). Once an r-AAA is suspected in the emergency room, the on-call vascular surgeon and the operating room are emergently notified (Figure 1). While in the emergency room, hemodynamically stable patients undergo an expeditious CT scan and are then transferred to the operating room equipped with fluoroscopic equipment, and the operating room staff is prepared for endovascular and open surgical AAA repair. Hemodynamically unstable patients with systolic blood pressure <80 mm Hg and a suspected r-AAA are directly transferred to the operating room without a preoperative CT scan.
All procedures were performed in the operating room with general anesthesia via bilateral femoral cutdown. The stent grafts used were the "at-the-time" Food and Drug Administration-approved AneuRx (Medtronic, Santa Rosa, CA), Excluder (Gore & Associates, Flagstaff, AZ), and Zenith (Cook Incorporated, Bloomington, IN), and available "off-the-shelf" devices. The particular stent grafts were chosen at the discretion of the surgeon based primarily on the anatomical limitations of the patient's aortoiliac morphology.
After femoral artery cutdown, ipsilateral access is achieved into the descending thoracic aorta using a floppy guidewire and a guiding catheter. The floppy guidewire is then exchanged for a super-stiff wire, which is then used to place a large sheath (12-22 F) in the ipsilateral femoral artery. A 33-mm or 40-mm compliant Equalizer occlusion balloon catheter (Boston Scientific Corporation, Natick, MA) is advanced over the super-stiff wire up to the supraceliac abdominal aorta under fluoroscopic guidance and is not inflated. Subsequently, access is achieved from the contralateral femoral cutdown, and an arteriogram was obtained to better define the aortoiliac morphology. Unless anatomically prohibitive, the femoral artery contralateral to the site of the aortic occlusion balloon is used for the stent graft main body. The aortic occlusion balloon is exchanged for a marker flush catheter, and an aortogram is obtained to better define the aortic neck morphology. The remainder of the EVAR was conducted in routine fashion.
We routinely employ the technique of hypotensive hemostasis in all patients with r-AAAs by limiting resuscitation and maintaining a detectable blood pressure to limit the potential for ongoing hemorrhage.11,12 Earlier in our experience, patients were systemically placed on heparin during EVAR for r-AAAs, although we no longer anticoagulate patients during these procedures. We found an increased activated partial thromboplastin time (a-PTT) to be a significant risk factor for development of abdominal compartment syndrome in these patients.13 In patients with hemodynamic instability or anatomic limitations that precluded expeditious exclusion of the r-AAA, modular bifurcated stent grafts were converted to aorto-uni-iliac devices by deploying aortic cuffs (AneuRx, Excluder, or Zenith aorto-uni-iliac converter) across the stent graft flow-divider. The contralateral iliac artery was interrupted by open ligation, endoluminal occlusion, or placement of a covered stent from the internal iliac artery into the external iliac artery, and femoral-femoral bypass was performed. Perioperative data were prospectively collected in a vascular surgery registry to analyze the outcomes of patients undergoing endovascular repair for r-AAAs.
Since 2002, 51 patients presented to our institution with r-AAAs and underwent EVAR. Overall, EVAR was attempted in 53 patients, and two patients (3.8%) in our earlier experience were converted to open surgical repair due to technical difficulties encountered during the procedure that precluded expeditious r-AAA exclusion. During the emergent open surgical conversion, a compliant aortic occlusion balloon catheter was left at the level of the supraceliac aorta and was ready for aortic occlusion, if needed. Fifty-one patients with r-AAAs underwent EVAR with the AneuRx (n=9; 18%), Excluder (n=36; 71%), or the Zenith (n=6; 11%) stent grafts. The mean age was 73 years (range, 54-88 years), and pre-existing comorbidities included coronary artery disease (n=32; 65%), hypertension (n=30; 58%), chronic obstructive pulmonary disease (n=9; 18%), renal insufficiency not on dialysis (n=3; 6%), and diabetes (n=12; 24%). The mean time from the presumptive diagnosis of r-AAA in the emergency room to the operating room for EVAR was 20 minutes (range, 10-35 minutes), and the mean operative time from skin incision to closure was 80 minutes (range, 35-125 minutes) (see Tables 1 and 2 for perioperative variables and morbidity/mortality rates for endovascular r-AAA repair). During a mean follow-up of 17 months, three patients with endovascular r-AAA repair required four secondary procedures.
The mortality rate of open surgical repair or r-AAAs remains notably high, ranging from 32% to 70%.9,10 Endovascular r-AAA repair is evolving and offers the potential for improved outcomes in patients who otherwise have high morbidity and mortality rates. In our experience, a multidisciplinary approach that involves the vascular surgeon, emergency room physicians, anesthesiologists, operating room staff, radiology technicians, the availability of a variety of available "off-the-shelf" stent grafts, and an operating room that is adequately equipped to perform endovascular procedures are crucial in obtaining better outcomes.
After establishing a protocol for endovascular treatment of r-AAA, we were able to expedite the recognition and treatment of patients with r-AAA, often without a preoperative CT scan. The resulting survival rate of 84% is markedly improved when compared to the historical data of open surgical repair for AAA rupture. In our experience, 24% of the patients with r-AAA were hemodynamically unstable and did not have a preoperative CT scan to evaluate their aortoiliac morphology prior to EVAR, and all patients were treated with commercially available "off-the-shelf" stent grafts with a standardized endovascular approach.
We recommend that prior to establishing endovascular means as the preferred method for treating r-AAAs, it is important to establish a standardized approach and obtained an adequate inventory of commercially available stent grafts, catheters, wires, balloons, sheaths, and fluoroscopic equipment in the operating room. A large inventory of stent grafts is not necessary crucial for treating patients with r-AAAs.
Our recommendations are: (1) surgeons/interventionists should be comfortable performing EVAR under elective circumstances; (2) obtain an inventory of standard equipment (wires, catheters, sheaths, balloons, particularly large compliant aortic occlusion balloons, and fluoroscopic equipment) before attempting endovascular repair of r-AAAs; (3) initially use the stent grafts that you are most comfortable using and get the sizes to match the largest aortic neck diameter, the shortest aneurysm length, and a variety of iliac extensions; (4) rehearse the procedure with all health care providers that would be involved in treating patients with r-AAAs, and establish a uniform triage protocol (Figure 1).
As long as the patients maintained a measurable blood pressure, the technique of hypotensive hemostasis and limiting resuscitation to maintain a detectable blood pressure helps minimize ongoing hemorrhage and cuts down on the transfer time to the operating room.11,14 These standardizations led to an acceptable transfer time (mean, 20 minutes) of patients from the emergency room to the operating room. The decision to use a particular stent graft type and size is based on the patient's aortoiliac morphology. In 24% of patients who were hemodynamically unstable and did not have a preoperative CT scan, the device selection was based on intraoperative angiographic findings; we have routinely oversized the stent graft generously when sizing is based solely on intraoperative arteriographic findings. Our goal in endovascular r-AAA repair has been to exclude the aneurysm at presentation and get the patient though the initial high-risk period, even at the cost of an elective secondary procedure or conversion to open surgical repair once the patient is hemodynamically stable. Although we did not use intravascular ultrasound guidance, one can speculate on its usefulness in identifying proximal and distal stent graft landing sites in patients without preoperative CT scan. With this approach, we have been successful in 96% of patients (51 of 53) who underwent an attempted EVAR for rupture.
At a mean follow-up of 17 months, the incidence of secondary interventions in 43 survivors was only 14% (six procedures in four patients), and elective open surgical conversion was 2% (one patient). None of these patients requiring secondary procedures had any significant morbidity/mortality. In the setting of hemodynamic instability or anatomical limitations that precluded expeditious exclusion of the r-AAA, temporary use of an aortic occlusion balloon was required in eight (16%) patients.
Our preferred method for placing aortic occlusion balloons is to use the femoral approach, and we have found this to have several advantages: (1) it allows the anesthesia team to have access to both upper extremities for arterial and venous access; (2) the patients who require the aortic occlusion balloon are often hypotensive and, in these patients, percutaneous brachial access can be difficult and more time consuming than femoral cut-down; and (3) the currently available aortic occlusion balloons require at least a 12-F sheath, which requires a brachial artery cut-down and repair, and stiff wires and catheters across the aortic arch without prior imaging under emergent circumstances might lead to other arterial injuries and/or embolization causing stroke. When using the femoral approach, distal migration of the aortic occlusion balloon by the blood flow can be prevented by placing the balloon through a long 12-F sheath (at least 55-cm length). Once the tip of the sheath is placed in the distal thoracic aorta, just below the level of the aortic occlusion balloon, it can be used to support the occlusion balloon and prevent distal migration. Once the stent graft is adequately positioned at the aortic neck, the occlusion balloon is deflated and withdrawn with the sheath into the aortic aneurysm sac (while maintaining wire access), and the stent graft is deployed.
In our experience of endovascular r-AAA repair, the incidence of ACS is much higher (eight of 51 patients, 16%) than previous reports. Furthermore, 50% (four of eight) of patients with ACS had emergent conversion of bifurcated stent grafts into aorto-uni-iliac devices due to ongoing hemodynamic instability during the procedure. One can speculate that a higher incidence of ACS might be related to the fact that similar to hemodynamically stable patients with r-AAAs, we also treated hemodynamically unstable patients by endovascular means. The resulting overall mortality rate was 16% (eight of 51), however, patients without ACS experienced far less mortality (three of 43 patients; 7%) when compared to those with ACS (five of eight patients; 63%).
Manish Mehta, MD, MPH, is from The Institute for Vascular Health and Disease, The Vascular Group, PLLC, Albany, New York. He has disclosed that he receives grant/research funding from Gore, Medtronic, and Cordis Endovascular. Dr. Mehta may be reached at (518) 262-5640; email@example.com.
Dr. Mehta's coauthors are from The Institute for Vascular Health and Disease, The Vascular Group, PLLC, Albany, New York. Dr. Darling has disclosed that he receives grant/research funding from Gore. Dr. Kreienberg has disclosed that he is a paid consultant and receives grant/research funding from Bard and Gore. Dr. Shah has disclosed that he receives grant/research funding from Gore.