Guy DeRose

Cumulative sum failure analysis of the learning curve with endovascular abdominal aortic aneurysm repair

PURPOSE The purpose of this study was to evaluate the importance of experience and the learning curve with endovascular abdominal aortic aneurysm (AAA) repair. METHODS A retrospective analysis was performed of all elective endovascular AAA repairs attempted by an individual surgeon and radiologist over a 4-year period. The primary outcome variable was achievement and 30-day maintenance of initial clinical success as defined by the Society for Vascular Surgery/American Association of Vascular Surgery reporting standards. Following standard statistical analysis, the cumulative sum (CUSUM) method was used to analyze the learning curve, with a predetermined acceptable failure rate of 10% and calculated 80% alert and 95% alarm lines. RESULTS Ninety-six elective endovascular AAA repairs were attempted by this team between 1998 and 2002 (mean age 74 +/- 0.8 years; mean aneurysm diameter 5.98 +/- 0.8 cm). Initial clinical success was achieved and maintained in 85 of 96 patients (88.5%). Although results were acceptable throughout the study period, improved results with respect to the target failure rate (10%) were not achieved until 60 patients were treated. The learning or CUSUM curves did not differ for different device manufacturers, with improved results being achieved following 20 implantations of each device. The results did differ when comparing aortouniiliac grafts (n = 27) and bifurcated grafts (n = 64). Results with bifurcated grafts remained consistent throughout the study period, whereas with aortouniiliac grafts, results improved after only a few procedures in comparison with the target failure rate. CONCLUSION Success rates with endovascular aneurysm repair will improve with an individuals experience. The CUSUM method is a valuable tool in the evaluation of this learning curve, which has credentialing and training implications. Although acceptable results were obtained throughout the study period, this analysis indicates that 60 endovascular aneurysm repairs, or 20 with an individual device, are necessary before optimal rates of initial clinical success can be achieved. These results can be achieved more readily with aortouniiliac grafts than with bifurcated grafts.

Technical factors are strongest predictors of postoperative renal dysfunction after open transperitoneal juxtarenal abdominal aortic aneurysm repair.

OBJECTIVE Juxtarenal abdominal aortic aneurysms (AAAs) have predominantly been repaired using an open technique. We present a series of patients with juxtarenal AAAs and analyze multiple factors predictive of postoperative renal dysfunction. METHODS Between March 2000 and September 2011, all patients in our prospectively maintained database undergoing juxtarenal AAA repair were evaluated for demographics, operative details, and in-hospital outcomes. Postoperative renal dysfunction was classified using the RIFLE (risk, injury, failure, loss, end-stage renal disease) criteria (glomerular filtration rate decrease >25%). The relationship between perioperative factors and postoperative renal dysfunction was explored using both univariate and multivariate analysis (logistic regression). RESULTS Of 169 patients, 76 (45%) required clamping above one renal artery, whereas 93 patients (55%) required clamping above both renal arteries. Mean (standard deviation) renal ischemia time was 29.2 (8.9) minutes (range, 12-65 minutes). Twenty-seven patients (16%) underwent adjunctive renal procedures, 19 (11.3%) required left renal vein division, and 130 (76.9%) received intraoperative mannitol. Postoperative renal dysfunction occurred in 63 patients (37.3%), with the majority (69%) resolving during hospital stay. Seven patients (4.1%) required postoperative dialysis, which was permanent in two cases. Patients who developed postoperative renal dysfunction had significantly longer mean renal ischemia times (34.7 [9.3] minutes vs 25.9 [6.6] minutes; P < .001), a higher rate of bilateral suprarenal aortic clamping (68.3% vs 47.2%; P = .008), higher rates of adjunctive renal artery procedures (26.7% vs 8.8%; P = .002), and higher rates of left renal vein division (20.6% vs 5.7%; P = .003). Logistic regression identified left renal vein division, renal ischemia time, and aortic clamp position as the strongest predictors of renal dysfunction. The use of mannitol was seen to be protective. Overall in-hospital mortality was 4.1% and was 9.5% among patients with postoperative renal dysfunction. CONCLUSIONS Postoperative transient renal dysfunction occurred in 37.3% of patients after open juxtarenal AAA repair, with a low incidence of dialysis and a low rate of permanent dysfunction. Technical factors including renal ischemia time, aortic clamp position, and left renal vein division are the strongest predictors of renal dysfunction. The use of intraoperative mannitol was associated with decreased postoperative renal dysfunction.

Intestinal mucosal permeability to 51Cr-ethylenediaminetetraacetic acid is increased after bilateral lower extremity ischemia-reperfusion in the rat*

BACKGROUND Despite successful revascularization of ischemic extremities, multiorgan dysfunction syndrome develops in some patients. Mechanisms responsible for this are not known; however, the gastrointestinal tract has been implicated as a possible mediator. Our objective was to demonstrate increased intestinal mucosal permeability after bilateral hindlimb ischemia-reperfusion (I-R) in a rodent model. METHODS Sixteen male Wistar rats were randomized either to 4 hours of bilateral hindlimb tourniquet ischemia and 24 hours of reperfusion (n = 8) or control groups (n = 8). The animals received 10 MuCi 51Cr-ethylenediaminetetraacetic acid (EDTA) by gavage, and excretion was measured in urine collected every 8 hours in 16 animals and every 4 hours in 8 animals. Arterial blood pressure was monitored continuously. Intravenous normal saline solution (3 ml/hr) with fentanyl (2 microgram/100 gm/hr) was continuously administered. Immediately before death complete blood count and levels of arterial lactate, creatinine, and urea were obtained. Mesenteric lymph nodes were harvested from the ileocecal region and cultured. Distal small bowel and proximal colon were preserved for histologic analysis. An additional 11 rats, six experimental and five control, were evaluated for mesenteric lymph node cultures only. RESULTS Urinary excretion of 51Cr-EDTA was significantly greater in the I-R group between 0 and 8 hours (p < 0.02) and 8 to 16 hours (p < 0.0002) of reperfusion. This increase occurred as early as 4 to 8 hours of reperfusion (p < 0.0001). Urine volume in the I-R group was significantly reduced during 0 to 4 hours of reperfusion (p < 0.002). Hemoglobin and lactate level were significantly different in the I-R group. Leukocyte and platelet counts, levels of creatinine and urea, and colony counts from mesenteric lymph nodes were similar in I-R and control groups. Blinded histologic analysis of bowel segments did not reveal morphologic differences. CONCLUSIONS Bilateral hindlimb I-R produces remote intestinal mucosal injury shown by significantly increased permeability to 51Cr-EDTA. Such increased mucosal permeability may be important in the development of multiorgan dysfunction syndrome in patients who sustain lower extremity I-R injury.

Aortic dilatation after endovascular repair of blunt traumatic thoracic aortic injuries

OBJECTIVE Endovascular repair of blunt traumatic thoracic aortic injuries (BTAI) has become routine at many trauma centers despite concerns regarding durability and aortic dilatation in these predominantly young patients. These concerns prompted this examination of thoracic aortic expansion after endovascular repair of a BTAI. METHODS The immediate postoperative and most recent computed tomography (CT) scans of patients who had undergone urgent endovascular repair of a BTAI and had at least 1 year of follow-up were reviewed. Diameter measurements were made at four predetermined sites: immediately proximal to the left subclavian artery (D1), immediately distal to the left subclavian artery (D2), distal extent of the endograft (D3), and 15 mm beyond the distal end of the endograft (D4). Split screens permitted direct comparison of measurements between CTs at the corresponding levels. RESULTS During a 6-year period (2001-2007), 21 patients (mean age, 42.9 years; range, 19-81 years) underwent endovascular repair of a BTAI, 17 with at least 1 year of follow-up (mean, 2.6 years; range, 1-5.5 years). No patients required reintervention during this period. The mean rate of dilatation for each level of the thoracic aorta in mm/year was: D1, 0.74 (95% confidence interval [CI], 0.42-1.06); D2, 0.83 (95% CI, 0.55-1.11); D3, 0.63 (95% CI, 0.37-0.89); D4, 0.47 (95% CI, 0.27-0.67). The rate of expansion of D2 differed significantly vs D4 (P = .025). CONCLUSIONS During the first several years of follow-up, the proximal thoracic aorta dilates minimally after endovascular repair of BTAIs, with the segment just distal to the left subclavian artery expanding at a slightly greater rate. Longer-term follow-up is necessary to determine whether this expansion continues and becomes clinically significant.

Trends in management of abdominal aortic aneurysms

OBJECTIVE The purpose of this study was to evaluate patients undergoing elective repair of infrarenal abdominal aortic aneurysms (AAAs) and the longitudinal trends in surgical management (open repair vs endovascular aneurysm repair [EVAR]), factors associated with the choice of surgical technique, and differences in the rate of in-hospital mortality at a single large-volume Canadian center. METHODS This retrospective cohort study used data from a prospectively collected vascular surgery database and reviewed all patients undergoing elective repair of an infrarenal AAA over a recent 10-year period (June 2000-May 2010). Information was reviewed regarding surgical techniques, patient demographics, and short-term outcomes. Subsequent analysis included univariate statistics and multivariable logistic regression with data presented as odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS A total of 1942 patients underwent elective AAA repair over this 10-year study period, 1067 (54.9%) via open repair and 875 (45.1%) via EVAR. The proportion of patients undergoing EVAR was significantly higher in the latter half of the study period compared to the first half (55.8% vs 33.9%; P < .01). Older patients (75 vs 71; P < .01) and those with higher American Society of Anesthesiologists classifications (P < .01) were more likely to receive endovascular repair than open repair. The overall in-hospital mortality rate in the entire cohort was low (2.3% for EVAR and 3.9% for open repair), and after multivariable logistic regression and adjustment for preoperative factors, in-hospital mortality was significantly higher in patients with open AAA repair (OR, 1.8; 95% CI, 1.04-3.13; P = .04). CONCLUSIONS This 10-year analysis shows a significant shift toward an endovascular approach in the repair of infrarenal AAAs at our Canadian center. Similar to other jurisdictions, higher risk and older patients are more likely to be treated with an endovascular repair resulting in a survival advantage in these patients compared to standard open repair.

Similar failure and patency rates when comparing one- and two-stage basilic vein transposition

OBJECTIVE Basilic vein transposition is recommended in patients who are not candidates for a radial or brachial artery to cephalic vein fistula for dialysis access. Both one-stage and two-stage procedures have their advantages and disadvantages. Which procedure results in improved outcomes remains unclear. METHODS A systematic review was conducted of the MEDLINE and EMBASE databases for studies that compared one-stage and two-stage brachial-basilic vein transpositions. Abstracts and full-text studies were screened independently by two reviewers with data abstraction done in duplicate. Random-effects meta-analysis was used to identify differences in primary failure rates and 1-year primary and secondary patency rates. Study quality was assessed by a previously described tool designed for observational studies reporting on dialysis access outcomes. RESULTS Of 1662 abstracts screened, 97 were selected for full-text review. Of these, eight studies (one randomized trial, seven observational studies) involving 882 patients met the inclusion criteria. The pooled odds ratio estimate for primary failure was 1.21 (95% confidence interval [CI], 0.73-1.98; P = .46), suggesting no difference in failure rate between one-stage and two-stage transpositions. Similarly, the estimated odds ratio for 1-year primary patency rate of 1.39 (95% CI, 0.71-2.72; P = .33) and 1-year secondary patency rate of 1.02 (95% CI, 0.36-2.87; P = .98) indicated no difference between the two groups. Study quality was limited by unclear outcome definitions, minimal control for confounding, and variable selection criteria. The decision to pursue a one-stage vs a two-stage procedure was often based on size of the basilic vein, with a two-stage procedure reserved for patients with smaller veins. CONCLUSIONS Meta-analysis of the existing literature comparing one-stage and two-stage basilic vein transposition suggests no difference in failure and patency rates, despite the two-stage procedures being used in patients with smaller basilic veins. These findings are limited by the small size, observational design, and inconsistent quality of included studies. Reserving a two-stage procedure for patients with smaller basilic veins appears justified, although the strength of the evidence is limited.

Early Mortality Following Endovascular Versus Open Repair of Ruptured Abdominal Aortic Aneurysms

Purpose: To determine whether endovascular repair (EVAR) offers a survival advantage over open repair (OAR) with ruptured abdominal aortic aneurysms (RAAA). Methods: Retrospective analysis of RAAA patients treated between 2003 and 2008. Univariate and multivariate analyses were performed. Results: 167 patients presented with RAAA (OAR = 135, 80.8%, EVAR = 32, 19.2%). On univariate analysis, EVAR was associated with a decreased mortality relative to OAR, (15.6% vs 43.7%, P = .004). Patients who survived were younger (P < .0005), had a higher blood pressure (P < .0005), level of consciousness (P < .0005), and hemoglobin (P = .018), and a lower urea (P = .005) and international normalized ratio (INR; P = .001). On multivariate analysis, type of repair remained an independent predictor of 30-day mortality (OR: 0.121; 95% CI: 0.021-0.682, P = .017). Conclusion: Controlling for preoperative factors, EVAR is an independent predictor of lower 30 day mortality relative to open repair after RAAA. This supports the wider use of endovascular repair in all patients with RAAA.

Durability and survival are similar after elective endovascular and open repair of abdominal aortic aneurysms in younger patients.

OBJECTIVE The role of endovascular repair (EVAR) of aortic aneurysms in young patients is controversial. The purpose of this study was to determine the long-term outcomes and reintervention rates in patients 60 years of age or younger who underwent elective open or endovascular repair of an abdominal aortic aneurysm. METHODS Retrospective review of a prospectively collected vascular surgery database at a university-affiliated medical center was performed to identify all patients who underwent elective repair of an abdominal aortic aneurysm between 2000 and 2013 and were 60 years of age or younger at the time of the repair. Preoperative anatomic measurements were performed and compared with instructions for use (IFU) criteria for the endografts. RESULTS The study cohort comprised 169 patients 60 years of age or younger (mean age, 56.7 ± 2.8 years) who underwent elective repair (119 open repair, 50 EVAR). Patients treated with open repair and EVAR had similar comorbidities, except that EVAR patients were more likely to have hypertension (P = .03) and poor left ventricular function (P = .04). The open repair group had significantly larger suprarenal (P = .004) and infrarenal (P = .005) neck angles, shorter neck lengths (P < .001), and larger maximum aneurysm diameter (P = .02) compared with the EVAR group. Only five patients (13%) in the EVAR group did not meet all IFU criteria. The overall in-hospital mortality rate was 1.8% (0% EVAR, 2.5% open repair; P = .56). Overall mean life expectancy was 11.5 years (9.8 years EVAR, 11.9 years open repair; P = .09). The 1-year (98% EVAR, 96% open repair), 5-year (86% EVAR, 88% open repair), and 10-year (54% EVAR, 75% open repair) survival did not differ between EVAR and open repair (P = .16). Long-term survival (78% EVAR, 85% open repair; P = .09) and reintervention rates (12% EVAR, 16% open repair; P = .80) did not differ. No late aneurysm rupture or aneurysm-related deaths were observed. The most common causes of long-term mortality were malignant disease and cardiovascular events. Reinterventions in the open repair group were exclusively laparotomy related (incisional hernia repairs), whereas all reinterventions in the EVAR group were aortic related, including one conversion to open repair. CONCLUSIONS After elective aneurysm repair, younger patients have a moderate life expectancy related to malignant disease and cardiovascular health. EVAR offers durability and long-term survival similar to those with open repair in these younger patients as long as aneurysm anatomy and IFU are adhered to.

Early results from a Canadian multicenter prospective registry of the Endurant stent graft for endovascular treatment of abdominal aortic aneurysms.

Purpose To report the early results of a multicenter registry of endovascular aneurysm repair (EVAR) using the Endurant stent-graft. Methods Patients having elective treatment of infrarenal abdominal aortic aneurysm (AAA) with the Endurant stent-graft at 3 Canadian centers were enrolled in a prospective registry between September 2008 and January 2010. In the 16-month period, 111 patients (90 men; mean age 75 years, range 53–93) were registered. Thirty-seven (33.3%) patients had challenging anatomy: short proximal aortic necks (n = 17), large diameter (>28 mm) aortic necks (n = 4), angulated (>60°) necks (n=3), and small (<15 mm) external iliac arteries (n=21). Outcomes evaluated included survival, endoleak, aneurysm expansion >5 mm, secondary intervention, stent-graft migration, and graft thrombosis. Results The overall technical success rate was 100%. Nineteen (17.1%) patients experienced perioperative complications. After a mean follow-up of 6 months (range 0.1–16), mortality in the series was 4.5%: 1 perioperative death (multisystem organ failure) and 4 (3.6%) late deaths (3 cardiac, 1 cancer). Clinical and imaging follow-up past the perioperative period were available in 107 (96.4%) and 99 (89.2%) patients, respectively. Among the latter, 9 (9.1%) had a type II endoleak on the first scan; 4 resolved spontaneously. Three (3.0%) patients developed graft limb thrombosis in follow-up; one required an intervention. There was no graft migration, aneurysm expansion, secondary intervention for endoleak, aneurysm rupture, or conversion. Conclusion Early results from this prospective multicenter registry indicate that the Endurant stent-graft is a safe option for elective EVAR in selected AAA patients. Longer follow-up is required to determine the durability of these outcomes.

Primary Aorto/Iliac-Enteric Fistula: Report of 6 New Cases:

The management of patients with vascular-enteric fistulas remains a challenging diagnostic and therapeutic problem for the vascular surgeon. Although fortunately quite a rare cause of gastrointestinal bleeding, reported mortality and amputation rates are very high. Fistulas between major vascular structures and the gastrointestinal tract are classified as either primary or secondary. Primary fistulas occur most commonly between an aortic aneurysm and the distal duodenum, while secondary fistulas occur following erosion of prosthetic material into the bowel following aortic reconstruction. The authors report 6 new cases of primary aortoenteric fistula: A malignant aortoenteric fistula in a patient with advanced metastatic squamous cell carcinoma involving the infrarenal aorta and duodenum, 4 cases of primary aortoenteric fistulas in patients with abdominal aortic aneurysms, and 1 iliac-enteric fistula secondary to a common iliac aneurysm. The diagnosis is often difficult to make, and although it was considered in 4 patients preoperatively, the diagnosis was not made until the time of laparotomy in all of these patients. Three patients were treated with an in-situ vascular graft, 2 others had the distal abdominal aorta oversewn and axillobilateral femoral bypass performed, and in the case involving the malignancy, the patient underwent primary aortic repair owing to the extent of the tumor process prohibiting aortic reconstruction. Three patients had primary closure of the intestine performed, and 3 required bowel resection and primary anastomosis. The overall 30-day mortality rate was 50% as 3 patients died in the early postoperative period and the remaining 3 patients survived to be discharged from hospital. One patient (17%) required bilateral above-knee amputations. Treatment of patients with vascular-enteric fistulas is a difficult problem, often associated with delayed diagnosis and high morbidity and mortality rates. Successful surgical management can be achieved with primary closure of the intestinal tract and an in-situ vascular graft or extraanatomic bypass.