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ENDOVASCULAR REPAIR
OF ABDOMINAL AORTIC ANEURYSMS:
SOUTHWEST METHODIST TEXAS HOSPITAL
EXPERIENCE 2000-2004
INTRODUCTION
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| Fig.1 Abdominal AorticAneurysm depicted on catheter angiogram |
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Abdominal aortic aneurysms (AAAs) (Fig 1.) affect approximately 1.5 million people in the United States, with an additional 190,000 new diagnoses each year. Rupture of abdominial aortic aneurysms (Figure 2)are associated with a high rate of mortality ( ~approximately 90%). Ruptured AAA's result in ~10,000 deaths each year and are presently the 10th leading cause of death in the western world. Although the risk of rupture has been reported to be low in small AAAs (~1%-5%/year for AAA 4-5 cm), the risk increased substantially as the aneurysm grows (25-40%/yr for an AAA 7-8 cm. Therefore, it is important to consult with patients about their treatment options as soon as an AAA is detected and diagnosed.
Risk factors for AAAs include advance age, male gender, smoking and family history. Although most AAAs go unnoticed by patients and physicians, they are often discovered during physical exam (pulsating, tender abdominal mass), and are further characterized by ultrasound and CT scanning (Fig 1). AAAs are most often identified in t he sixth, seventh, and eighth decades of life and recent guidelines recommend screening for all males 60-85 yearsof age, all females 60-85 years of age with cardiovascular risk factors and male and female 50 years of age and older with family history of AAA (Kent, KG et al. J Vascular Surg. 2004; 39(1): 267-269).
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| Fig.2 Ruptured abdominal aortic aneurysm with surrounding hemorrhage |
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TREATMENT OPTIONS:
Currently, two options exist for AAA treatment: 1) open surgical repair, in which an abdominal incision is made and the aneurysm is repaired with a graft sutured to the native aorta or 2) endovascular aneurysm repair (EVAR), in which small groin incisions are made and a self-expanding stent-graft (Figure 2) is inserted via tubes into the aortic aneurysm aorta deployed using x-ray guidance. The sten-graft is flexible and coforms to the patients anatomy. The stent-graft allows blood to flow through it, into the iliac(leg) arteries and seals off the aneurysm. The stent-graft is anchored to a normal part of the patients aorta, preventing it from moving. The stent-graft remains in place indefinitely and is observed and monitored via a CAT-scan. The aneurysm is also monitored for change in size and shape (Fig 4).
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| Fig.3 The Aneuryx stent-graft: main body on the left with modular components shown on the right. |
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| Figures 4 and 5: Interval shrinkage of abdominal aortic aneurysm following stent-graft repair |
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Open surgical repair of AAAs has been practiced since the mid 1950's with much success, but some patients are not candidates for this surgery based on the increased morbidity and mortality associated with the common chronic comorbidities present in this patient populations such as coronary artery disease (CAD), Chronic Obstructive Pulmonary Disease (COPD), hypertension, diabetes and renal insufficiency.
EVAR has been approved by the FDA for the treatment of AAAs in the United States since 1999, and offers a reliable alternative for patients who meet the vascular anatomy and AAA location requirements and for those who are not candidates for open surgical repair. EVAR is also a less invasive treatment than open surgical repair: it is associated with lower mortality and morbidity, less blood loss during surgery, shorter hospital stays and shorter recovery periods.
Current guidelines for the treatment of abdominal aortic aneurysms (Journal of Vascular Surgery, Vol 37, Number 5, pp. 1106-1117) recommend 5.5 cm diameter aneurysm as the best threshold for repair in the "average patient". Treating smaller aneurysms may be justified in younger good risk patients, aneurysms at higher rupture risk, and in women with smaller aneurysms. The choice between EVAR and open is difficult and may be advantageous for older, high risk patients with suitable anatomy. Until the long-term results of EVAR is better defined, the choice between EVAR and open repair will continue to rely heavily on patient preference.
SOUTH WEST TEXAS METHODIST HOSPITAL AAA EXPERIENCE WITH EVAR
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| Fig.6 EVAR team comprised of an interventional radiologist and vascular surgeon. |
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A total of 233 patients underwent AAA repair (148 open surgical repair, 85 EVAR) from February 2000 to October 2004 at the Southwest Texas Methodist Hospital , San Antonio, Texas. The following data illustrate a 56-month single center experience from our hospital in 85 patients who received EVAR for their AAA and were treated by Southwest Texas Radiology Group radiologists and Peripheral Vascular Associates surgeons. All EVAR procedures were performed by a team comprised of a radiologist and vascular surgeon. (Figure 6)
PATIENT AGE, AAA SIZE AND COMORBITIES
Of the 85 patients who received EVAR, 87% were female, while the average age was 74, with an age range from 45-49 to 95-100.
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| Fig.7 Age ranges vs. numbers of EVAR patients. |
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Many of these EVAR patients also displayed a variety of comorbidities at the time of repair. These included hypertension, CAD, dyslipidemia, cancer, COPD, arrythmias, bronchitis, asthma, and pneumonia. (Figure 8) The patient population treated at SW Texas Methodis Hospital had an average aneurysm size of 5.4 cm with a range from 4.2 cm to 7.7 cm.
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| Fig.8 Comorbidities associated with EVAR patients. |
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EVAR PROCEDURE OUTCOMES
The average length of the endovascular procedure was approximately 3 hours with blood loss averaging ~513 cc. Transfusions were infrequent, and were only required in 17% of patients (14), and consisted of 1.5 units of packed RBCs. No EVAR patient underwent conversion to open repair (0/85) and the 30 day post-operative mortality was 1.1% (1/85). This is similar to that reported in many clinical trials conducted at academic centers.
CONCOMITTANT OF ADJUNCTIVE PROCEDURES
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| Figures 9 and 10: Adjunctive procedures utilized during EVAR included stents in the iliac artery to the leg (left) and stent in the aortic end of the graft (right). |
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During the course of the EVAR procedure, it is often necessary to perform adjunctive procedures to maximize patency of the stent-graft and to ensure the best fit of the device inside the patient. Early on in our experience, we utilized a graft that would often require metallic stents in addition to the graft itself. Currently utilized devices may require modular components to extend the graft either at the limb attachment sites in the iliac arteries in the pelvis or where the device attaches in the aorta.
In our series, we report 59 device-related concomitant procedures in 85 patients. Most of these procedures were graft limb stents and limb extenders. Limb patency rate was similar in those who received limb stents (92%, with 8% requiring later revascularization) vs. those who did not receive limb stents (93%, with 6 % requiring intervention).
CHANGE IN AAA DIAMETER AND PRESENCE OF ENDOLEAKS
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| Fig.11 Type III endoleak identified on surveillance CT scans, treated with minimally invasive interventional radiology techniques with subsequent resolution. |
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Post operative imaging of AAA diameter after EVAR revealed shrinkage (Figures 4 and 5) or no change in the size of the AAA after EVAR in 89% of patients. Only 11 percent of patients showed some type of enlargement in their AAA, and the average enlargement was just 2.8mm. This compares favorably to recent literature (Brewster, et al, JVS, May 2003, pp 1106-1117) which reports that EVAR limited AAA expansion in 80-90% of patients. Our series has no cases in which the AAA ruptured after EVAR, vs literature rupture rates of 2-5% post EVAR. One issue with EVAR is the presence of what are known as endoleaks post procedure. These have been classified and several types, known as Types 1 and 3, need to be repaired prior to the end of the procedure (Type 1) or once discovered (Type 3). (Figure 11).
The most common type of endoleak, type II, arises from small blood vessels associated with the native aorta which reverse flow following treatment with EVAR. This type rarely causes adverse consequences.
In our series, endoleaks were identified by CT scan in 12 patients within 6 months following EVAR, 5 patients at 1 year, and only 4 patients at the 2 year follow-up. Nine endoleak patients are living and being followed; 3 others are living and not being followed. The average age of the endoleak patients is 74, 11 of 12 are male; their average AAA diameter is 5.0cm. At the time of EVAR in all 85 patients, there were only 10 concomitant procedures performed to deal with endoleaks; the majority of these procedures were stent placements. There was only one late procedure (out of 12 endoleaks detected) conducted to treat an endoleak in this patient cohort, that being a repair of a Type 1 endoleak (graft attachment leak).
SURVIVAL DATA
In total, for the period from February 2000 to October 2004, 74% of patients who received EVAR are living, 60% of these patients are actively being followed and 14% are not. Nine percent of patients have been lost to follow-up and 16% of patients have died.
CONCLUSIONS
Our team of physicians and support staff at the Southwest Texas Methodist Hospital consists of an experienced group of EVAR physicians who have been providing this type of treatment since it was approved by the FDA in 1999. They are familiar with the devices currently available and are experts in the noninvasive evaluation and workup of patients prior to the exam, have extensive intraprocedural skills and are able to monitor and treat the patients appropriately post procedure.
The patients who have undergone EVAR under our care in this 56 month time period have displayed excellent outcomes based on operative and post-operative follow-up. The data show a low rate of complications, mostly stable to shrinking AAA measurements post-EVAR and a very low mortality rate associated with the procedure.
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