Frank R. Arko

Type-II Endoleaks Following Endovascular AAA Repair: Preoperative Predictors and Long-term Effects

Purpose: To determine the significance of persistent type-II endoleaks and whether they can be predicted preoperatively in patients with abdominal aortic aneurysms (AAA). Methods: The charts of all AAA patients treated with the AneuRx stent-graft at a single center from 1996 to 1998 were reviewed. Patients with <12-month follow-up or type-I endoleaks were excluded. The presence or absence of type-II endoleaks was determined from duplex imaging and computed tomographic angiography. Three groups were identified and compared: 16 patients with persistent type-II endoleaks (PE), 14 patients with transient type-II endoleaks (TE), and 16 patients with no endoleak (NE). Results: The groups did not differ with regard to age, preoperative comorbidities, follow-up time, and AAA neck diameter and length. AAA diameters were 57.1 ± 9.0 mm for NE, 63.4 ± 11.4 mm for TE, and 55.6 ± 4.2 mm for PE. The inferior mesenteric artery (IMA) was patent in 5 (31%) NE patients, 6 (43%) TE patients, and 13 (81%) PE patients (p < 0.01). The number of patent lumbar arteries visualized preoperatively was 0.5 ± 1.0 in NE, 1.3 ± 0.8 in TE, and 2.4 ± 0.6 in PE (p < 0.0001). Patent IMAs (RR 0.82, p<0.01) and >2 lumbar arteries (RR 0.40, p < 0.0001) were identified as independent preoperative risk factors for persistent endoleaks. There were no changes in mean diameter or volume in aneurysms with persistent endoleaks. Conclusions: No adverse clinical events were related to the presence of type-II endoleaks, but there was no decrease in aneurysm size in patients with persistent type-II leaks. Patients with a large, patent IMA, or >2 lumbar arteries on preoperative CT angiography are at higher risk for persistent type-II endoleaks.

In Vivo Validation of Numerical Prediction of Blood Flow in Arterial Bypass Grafts

AbstractIn planning operations for patients with cardiovascular disease, vascular surgeons rely on their training, past experiences with patients with similar conditions, and diagnostic imaging data. However, variability in patient anatomy and physiology makes it difficult to quantitatively predict the surgical outcome for a specific patient a priori. We have developed a simulation-based medical planning system that utilizes three-dimensional finite-element analysis methods and patient-specific anatomic and physiologic information to predict changes in blood flow resulting from surgical bypass procedures. In order to apply these computational methods, they must be validated against direct experimental measurements. In this study, we compared in vivo flow measurements obtained using magnetic resonance imaging techniques to calculated flow values predicted using our analysis methods in thoraco–thoraco aortic bypass procedures in eight pigs. Predicted average flow rates and flow rate waveforms were compared for two locations. The predicted and measured waveforms had similar shapes and amplitudes, while flow distribution predictions were within 10.6% of the experimental data. The average absolute difference in the bypass-to-inlet blood flow ratio was 5.4±2.8%. For the aorta-to-inlet blood flow ratio, the average absolute difference was 6.0±3.3%.

How Many Patients with Infrarenal Aneurysms are Candidates for Endovascular Repair? The Northern California Experience

PURPOSE To determine how many patients with abdominal aortic aneurysms (AAA) meet the anatomical selection criteria for AneuRx stent-graft repair in community hospitals of Northern California. METHODS The records were reviewed of 220 AAA patients (171 men, 49 women) who were considered for endovascular repair by the treating vascular surgeon at 28 community hospitals in Northern California between January and October 2001. Contrast computed tomographic angiography (CTA) and selective arteriography were performed at each institution and reviewed by a centralized, independent image-reading center. Selection criteria determined by the manufacturer and published in the indications for use were applied to each set of imaging studies. The number of patients who met inclusion criteria were recorded, as were the anatomical characteristics of each aneurysm. RESULTS The mean aneurysm size in the 220 patients was 55.3 +/- 0.7 mm. Among these patients, 122 (55%) were judged to be candidates for endovascular repair and 98 (45%) were considered ineligible. The primary anatomical reason for ineligibility was a short infrarenal neck in 43 (44%) patients, followed by a large proximal neck diameter (25, 25%), iliac aneurysms (10, 10%), extremely tortuous or calcified neck (7, 7%), iliac occlusion (6, 6%), and small distal aortic bifurcation and accessory renal arteries (5, 5%). Four (4%) patients were classified as non-candidates due to poor quality imaging. There was no difference in aneurysm diameter (54.0 +/- 0.8 versus 57.1 +/- 1.2 mm, p=NS) or age (72.2 +/- 1.2 versus 74.6 +/- 2.2 years, p=NS) between candidates and non-candidates. However, proportionally more men (60%) than women (39%) were eligible for endovascular repair with the AneuRx stent-graft (p<0.05). All 122 patients who were considered candidates for endovascular repair were treated, with successful stent-graft placement achieved in 121 (99%). CONCLUSIONS Fifty-five percent of patients considered for endovascular AAA repair in community hospitals in Northern California met the anatomical selection criteria for the AneuRx stent-graft. Men appeared to be twice as likely to meet the eligibility requirements as women. Unfavorable infrarenal neck anatomy was the primary exclusion criterion for endovascular repair in this community setting.

Operative mortality for renal artery bypass in the United States: Results from the National Inpatient Sample

BACKGROUND The mortality rate for renal artery bypass grafting (RABG) is reported to be 0% to 4% for patients with renovascular hypertension and 4% to 7% for patients with ischemic nephropathy. However, these data come from high-volume referral centers known for their expertise in treating these conditions. Because of the relative infrequency of these operations in most vascular surgery practices, the nationwide outcomes for RABG are not known. The purpose of this study was to define the operative mortality rate for RABG in the United States and to identify risk factors for perioperative mortality. METHODS The National Inpatient Sample was analyzed to identify patients undergoing RABG for the years 2000 to 2004. Categoric data were analyzed using chi(2) and the Cochran-Armitage trend tests. Multivariate logistic regression analyses were performed to identify risk factors for perioperative mortality after RABG. RESULTS During the study period, 6608 patients underwent RABG, representing a frequency of 3.51 operations per 100,000 discharges. More than two-thirds were performed at teaching hospitals (4564 vs 2,044; P < .0001). The frequency of RABG decreased by 30.7% between 2000 and 2004 (4.28 vs 2.96 RABGs per 100,000 discharges; P for trend < .0001). The in-hospital mortality for RABG was 10.0%. On univariate analysis, in-hospital mortality after RABG varied with increasing age, race, region of the country, and a preoperative history of chronic renal failure, congestive heart failure, or chronic lung disease. Logistic regression models identified advanced age (odds ratio [OR] 1.57; 95% confidence interval [CI], 1.44-1.72], female gender (OR, 1.20; 95% CI, 1.02-1.41), and a history of chronic renal failure (OR, 2.21; 95% CI, 1.75-2.78), congestive heart failure (OR, 1.94; 95% CI, 1.44-2.62), or chronic lung disease (OR, 1.40; 95% CI, 1.18-1.67) as independent markers of risk-adjusted, in-hospital mortality (P < .0001 for each of these five variables). CONCLUSIONS Nationwide in-hospital mortality after RABG is higher than predicted by prior reports from high-volume referral centers. Advanced age, female gender, and a history of chronic renal failure, congestive heart failure, or chronic lung disease were predictive of perioperative death. For the typical vascular practice, these data may provide a rationale for lower risk alternatives, such as renal artery stenting or referral to high-volume referral centers for RABG.

Endovascular Repair of Acute Traumatic Thoracic Aortic Transection with Laser-Assisted In-Situ Fenestration of a Stent-Graft Covering the Left Subclavian Artery

Purpose: To report the use of in-situ laser-assisted endograft fenestration during thoracic endovascular aortic repair (TEVAR). Case Report: A healthy 26-year-old man presented to the emergency department after sustaining blunt chest trauma. He was hemodynamically stable, although he subjectively complained of tearing chest pain and pleuritic chest wall pain. Radiography revealed a left clavicular fracture, multiple rib fractures, and a widened mediastinum. Imaging showed a partially contained acute aortic transection just distal to the takeoff of the left subclavian artery (LSA); the arch had a bovine configuration, with a shared origin of the right innominate and left common carotid arteries. Endovascular repair was elected, but to avoid sacrificing the LSA, TEVAR with in-situ graft fenestration was performed to reduce the risk of posterior circulation stroke, spinal cord ischemia, and subclavian steal syndrome. A Talent thoracic stent-graft was deployed, with the covered portion of the endograft extending just distal to the shared origin of the innominate and left carotid arteries. A laser catheter was advanced through the LSA to fenestrate the endograft; the fenestration was dilated and stented with an iCast stent, which was flared proximally and distally to effect a seal. At 6 weeks, imaging documented that the repair was patent and secure; the patient continues to do well at his most recent follow-up at 8 months. Conclusion: This technique may provide a means for extending thoracic endografting technology to a greater number of patients with acute thoracic aortic pathology.

Left subclavian artery coverage during thoracic endovascular aortic aneurysm repair does not mandate revascularization

OBJECTIVE This study assessed the risk of left subclavian artery (LSA) coverage and the role of revascularization in a large population of patients undergoing thoracic endovascular aortic aneurysm repair. METHODS A retrospective multicenter review of 1189 patient records from 2000 to 2010 was performed. Major adverse events evaluated included cerebrovascular accident (CVA) and spinal cord ischemia (SCI). Subgroup analysis was performed for noncovered LSA (group A), covered LSA (group B), and covered/revascularized LSA (group C). RESULTS Of 1189 patients, 394 had LSA coverage (33.1%), and 180 of these patients (46%) underwent LSA revascularization. In all patients, emergency operations (9.5% vs 4.3%; P=.001), renal failure (12.7% vs 5.3%; P=.001), hypertension (7% vs 2.3%; P=.01), and number of stents placed (1=3.7%, 2=7.4%, ≥3=10%; P=.005) were predictors of SCI. History of cerebrovascular disease (9.6% vs 3.5%; P=.002), chronic obstructive pulmonary disease (9.5% vs 5.4%; P=.01), coronary artery disease (8.5% vs 5.3%; P=.03), smoking (8.9% vs 4.2%) and female gender (5.3% men vs 8.2% women; P=.05) were predictors of CVA. Subgroup analysis showed no significant difference between groups B and C (SCI, 6.3% vs 6.1%; CVA, 6.7% vs 6.1%). LSA revascularization was not protective for SCI (7.5% vs 4.1%; P=.3) or CVA (6.1% vs 6.4%; P=.9). Women who underwent revascularization had an increased incidence of CVA event compared with all other subgroups (group A: 5.6% men, 8.4% women, P=.16; group B: 6.6% men, 5.3% women, P=.9; group C: 2.8% men, 11.9% women, P=.03). CONCLUSIONS LSA coverage does not appear to result in an increased incidence of SCI or CVA event when a strategy of selective revascularization is adopted. Selective LSA revascularization results in similar outcomes among the three cohorts studied. Revascularization in women carries an increased risk of a CVA event and should be reserved for select cases.

Symptomatic ileofemoral DVT after onset of oral contraceptive use in women with previously undiagnosed May-Thurner Syndrome

OBJECTIVE May-Thurner syndrome is characterized by left common iliac obstruction secondary to compression of the left iliac vein by the right common iliac artery against the fifth-lumbar vertebra. This anatomic variant results in an increased incidence of left-sided deep venous thrombosis (DVT). Furthermore, while a preponderance of left-sided DVT has been demonstrated in women during pregnancy and oral contraceptive use, patients are not typically screened for this condition after developing a left-sided DVT. As anticoagulation alone is ineffective for DVT treatment in the setting of May-Thurner anatomy, more aggressive treatment is warranted. Failure to diagnosis this condition predisposes these women to the unnecessary risks of recurrent DVT and post-thrombotic syndrome. METHODS We present the occurrence of 7 adolescent patients with previously undiagnosed May-Thurner syndrome who presented with DVT after the initiation of oral contraceptive steroids (OCP) use. All 7 patients elected to proceed with mechanical thrombolysis/catheter based thrombolysis followed by endovascular stenting and were postoperatively treated with 6 months of warfarin. RESULTS Mean patient age was 18.3 +/- 3.3 years (range, 16-24 years). Mean time to presentation after initiation of OCP was 5 weeks (range, 2-10 weeks). Mean time to intervention was 16.8 days (range, 10-24 days). All patients were treated with mechanical thrombectomy. Our rate of intraoperative clot resolution was 100%. All 7 patients were treated with self expanding nitinol stents after angioplasty of the iliac vein stenosis with resolution of the stenotic segment. Primary stent patency is 100% (7/7). Mean follow-up time is 13 +/- 13.84 months (range, 6-42 months). There have been no long-term complications related to surgical treatment or anticoagulation. All 7 patients have experienced resolution of left leg swelling and pain and have no evidence of post-thrombotic syndrome or DVT recurrence to date. CONCLUSIONS Women on OCPs presenting with left-sided iliofemoral DVT should be screened for hypercoagulable disorders and underlying May-Thurner anatomy. Treatment of May-Thurner syndrome should include thrombolysis/thrombectomy and anticoagulation for current DVT in addition to angioplasty and stenting of the underlying obstruction.

Volumetric analysis of type B aortic dissections treated with thoracic endovascular aortic repair

BACKGROUND Type B aortic dissections are being successfully treated by thoracic endovascular aortic repair (TEVAR). Postoperative false lumen patency has been associated with aneurysmal dilatation and rupture of the thoracic aorta, necessitating further intervention. This is the first volumetric analysis of type B aortic dissections comparing patients with and without false lumen thrombosis (FLT) after TEVAR. We hypothesized that a greater increase in postoperative true lumen volume will lead to FLT, and without this change, false lumen patency will result. METHODS Preoperative and postoperative computed tomography angiography (CTA) imaging was analyzed using three-dimensional reconstruction to measure the short- and long-axis diameter and cross-sectional area of the true lumen, false lumen, and total aorta. Measurements were taken at 5-cm intervals from the left subclavian artery to the aortic bifurcation. Pre- and postoperative volumetric data were calculated and compared in patients with and without postoperative FLT. RESULTS Between 2006 and 2010, 132 patients underwent thoracic aortic stent grafting. Of these, 31 (23%) had thoracic endografting for type B aortic dissection. Pre- and postoperative CTA images were available for analysis in 23 patients with a mean age of 59 ± 14 years treated for acute, complicated (n = 8, 35%), and chronic (n = 15, 65%) indications. Mean follow-up imaging was 9 months (range, 1-39 months). Thirteen patients (56%) had postoperative FLT and 10 (43%) had persistent false lumen patency. The dissections involved the left subclavian artery (n = 12), visceral arteries (n = 14), renal arteries (n = 16), and iliac arteries (n = 15). The left subclavian artery was intentionally covered in 15 patients (65%). There were no significant differences in age, acute vs chronic dissection, branch vessel involvement, coverage of the left subclavian artery, or distal extent of the endograft between patients with and without postoperative FLT. Patients with postoperative FLT had a significantly smaller preoperative maximum thoracic aortic diameter (5.05 ± 1.0 vs 6.30 ± 1.4 cm; P = .02). Volumetric analysis demonstrated significantly smaller preoperative true lumen volume (141.3 ± 68 vs 230.5 ± 92 cm(3); P = .01) in patients with FLT, but no difference in preoperative false lumen volume. Patients with FLT had a significant increase in the volume percentage of the true lumen from 42.7% to 61.7% (P = .02) after stent graft repair, compared with an increase from 46.7% to 47.7% (P = .75) in patients with persistent false lumen patency. CONCLUSIONS This volumetric study of type B aortic dissection treated with TEVAR suggests that the ability of the endograft to significantly increase the true lumen volume as a percent of the total aorta most accurately predicts postoperative FLT. This is best demonstrated in a nonaneurysmal dissection regardless of timing since dissection.

Percutaneous Access for Endovascular Abdominal Aortic Aneurysm Repair: Can Selection Criteria Be Expanded?

Previous reports suggest that percutaneous access for endovascular abdominal aortic aneurysm repair (P-EVAR) is as safe as open access (O-EVAR) in patients with favorable femoral anatomy. Severe femoral artery calcification and obesity have been considered relative contraindications to P-EVAR, but these criteria have not been evaluated. The purpose of this study was to assess the postoperative anatomic changes associated with P-EVAR versus O-EVAR using three-dimensional (3-D) computed tomographic (CT) reconstruction and to evaluate the overall results of the two procedures in a group of patients with suboptimal femoral anatomy. During a recent 26-month period, 173 patients underwent EVAR at our institutions, including 35 P-EVARs. Of these, 22 (63%) had complete pre- and postoperative CT imaging of the femoral arteries. These subjects were compared to 22 matched controls who underwent O-EVAR during the same period. Automated 3-D reconstructions were used to measure the following anatomic femoral artery parameters before and after EVAR: arterial depth, calcification score, minimum diameter and area, and maximum diameter and area. Of the 88 study arteries, 50 underwent open access and 38 percutaneous access (Proglide, n=11; Prostar XL, n=27). Both groups were similar regarding sheath size, number of components, operative time, blood loss, and length of stay. Significantly more O-EVAR subjects suffered groin complications (p=0.02), including five hematomas, two wound infections, two femoral thromboses, and one vessel which required patch repair. In the P-EVAR group there was only one hematoma, which was managed conservatively. There was no difference between the P-EVAR and O-EVAR groups with respect to femoral artery calcification (Agatston scores 667+/-719 vs. 945+/-1,248, p=0.37). Obesity (body mass index >30) was documented in six (27%) of both the P-EVAR and O-EVAR groups (p=nonsignificant). Pre- and postoperative CT-derived anatomic data showed a significant decrease in the minimal vessel area with O-EVAR compared to P-EVAR (p=0.02). This study demonstrates that patients with obesity or severely calcified femoral arteries can be successfully treated percutaneously with fewer minor groin complications.

Outcome-based anatomic criteria for defining the hostile aortic neck

OBJECTIVE There is abundant evidence linking hostile proximal aortic neck anatomy to poor outcome after endovascular aortic aneurysm repair (EVAR), yet the definition of hostile anatomy varies from study to study. This current analysis was undertaken to identify anatomic criteria that are most predictive of success or failure at the aortic neck after EVAR. METHODS The study group comprised 221 patients in the Aneurysm Treatment using the Heli-FX Aortic Securement System Global Registry (ANCHOR) clinical trial, a population enriched with patients with challenging aortic neck anatomy and failure of sealing. Imaging protocols were not protocol specified but were performed according to the institutions standard of care. Core laboratory analysis assessed the three-dimensional centerline-reformatted computed tomography scans. Failure at the aortic neck was defined by type Ia endoleak occurring at the time of the initial endograft implantation or during follow-up. Receiver operating characteristic curve analysis was used to assess the value of each anatomic measure in the classification of aortic neck success and failure and to identify optimal thresholds of discrimination. Binary logistic regression was performed after excluding highly intercorrelated variables, creating a final model with significant predictors of outcome after EVAR. RESULTS Among the 221 patients, 121 (54.8%) remained free of type Ia endoleak and 100 (45.2%) did not. Type Ia endoleaks presented immediately after endograft deployment in 58 (58.0%) or during follow-up in 42 (42.0%). Receiver operating characteristic curve analysis identified 12 variables where the classification of patients with type Ia endoleak was significantly more accurate than chance alone. Increased aortic neck diameter at the lowest renal artery (P = .013) and at 5 mm (P = .008), 10 mm (P = .008), and 15 mm (P = .010) distally; aneurysm sac diameter (P = .001), common iliac artery diameters (right, P = .012; left, P = .032), and a conical (P = .049) neck configuration were predictive of endoleak. By contrast, increased aortic neck length (P = .050), a funnel-shaped aortic neck (P = .036), and neck mural thrombus content, as measured by average thickness (P = .044) or degrees of circumferential coverage (P = .029), were protective against endoleak. Binary logistic regression identified three variables independently predictive of type Ia endoleak. Neck diameter at the lowest renal artery (P = .002, cutpoint 26 mm) and neck length (P = .017, cutpoint 17 mm) were associated with endoleak, whereas some mural neck thrombus content was protective (P = .001, cutpoint 11° of circumferential coverage). CONCLUSIONS A limited number of independent anatomic variables are predictive of type Ia endoleak after EVAR, including aortic neck diameter and aortic neck length, whereas mural thrombus in the neck is protective. This study suggests that anatomic measures with identifiable threshold cutpoints should be considered when defining the hostile aortic neck and assessing the risk of complications after EVAR.