S.R. Vallabhaneni

Risk-adjusted outcome analysis of endovascular abdominal aortic aneurysm repair in a large population: how do stent-grafts compare?

Purpose: To compare differences in the applicability and incidence of postoperative adverse events among stent-grafts used for repair of infrarenal aortic aneurysms. Methods: An analysis of 6787 patients from the EUROSTAR Registry database was conducted to compare aneurysm morphological features, patient characteristics, and postoperative events for the AneuRx, EVT/Ancure, Excluder, Stentor, Talent, and Zenith devices versus the Vanguard device (control) and each other. Annual incidence rates of complications were determined, and risks were compared using the Cox proportional hazards analysis. Results: The annual incidence rates were: device-related endoleak (types I and III) 6% (range 4%-10%), type II endoleak 5% (range 0.3%-11%), migration 3% (range 0.5%-5%), kinking 2% (range 1%-5%), occlusion 3% (range 1%-5%), rupture 0.5% (range 0%-1%), and all-cause mortality 7% (range 5%-8%). After adjustment for factors influencing outcome, AneuRx, Excluder, Talent, and Zenith devices were associated with a lower risk of migration, kinking, occlusion, and secondary intervention compared to the Vanguard device. Significant increased risk for conversion (EVT/Ancure) and reduced risk of aneurysm rupture (AneuRx and Zenith) and all-cause mortality (Excluder) were found compared to the Vanguard device. Conclusions: Significant differences exist between stent-grafts of different labels in terms of applicability and complications during intermediate to long-term follow-up. Since each stent-graft has its drawbacks, no single label can be identified as the best. It is reassuring that developments in stent-grafts indeed result in better performance than the early stent-grafts. However, a single device incorporating all the perceived improvements should still be pursued.

Fenestrated endovascular repair for juxtarenal aortic aneurysm.

The outcome of fenestrated endovascular aneurysm repair (F‐EVAR) was evaluated.

Heterogeneity of tensile strength and matrix metalloproteinase activity in the wall of abdominal aortic aneurysms.

Purpose: To measure the tensile strength of the aneurysm wall and the matrix metalloproteinase (MMP) activity in similar samples of aortic tissue. Methods: Detailed mechanical testing was conducted on 124 standardized specimens of aneurysm wall harvested from 24 patients undergoing elective aneurysm repair. The intrasac pressure required to cause aneurysm rupture was calculated based upon the Law of Laplace. In addition, MMP-2 and 9 were assayed from these specimens. Sixty specimens of nonaneurysmal aorta from 6 cadaveric organ donors served as controls. Intrasubject and intersubject variations were analyzed. Results: In the aneurysm specimens, the Youngs modulus was 1.80times106 N/m2, the load at break was 6.36 N, the strain at break was 0.30, the ultimate strength was 0.53times106 N/m2, and the MMP activity was 312 for MMP-2 and 460 for MMP-9. In the controls, the circumferential measurements were a Youngs modulus of 1.82times106 N/m2, a load at break of 5.43 N, strain at break of 0.29, ultimate strength of 0.61times106 N/m2, and MMP activity of 395 for MMP-2 and 2019 for MMP-9. Longitudinal measurements in controls were a Youngs modulus of 1.38times106 N/m2, a load at break of 11.39 N, a strain at break of 0.33, and ultimate strength of 1.30times106 N/m2. Intra and intersubject variation of all parameters was very high. Based upon the lowest measured tensile strength for each aneurysm, the intrasac pressure required to cause rupture varied from 142 to 982 mmHg. Conclusions: Localized “hot spots” of MMP hyperactivity could lead to focal weakening of the aneurysm wall and rupture at relatively low levels of intraluminal pressure. These data suggest that tensile strength of the sac is just as important as intrasac tension in determining the risk of rupture. Moreover, these observations may explain why some small aneurysms rupture and larger aneurysms do not. Assessment of rupture risk based on computation or measurement of wall stress may be subject to error and inaccuracy due to variations in wall tensile strength.

Surveillance after EVAR based on duplex ultrasound and abdominal radiography.

INTRODUCTION Computed tomography angiography (CTA) is considered the gold standard imaging technique for surveillance following endovascular aneurysm repair (EVAR). Limitations of CTA include cost, risk of contrast nephropathy and radiation exposure. A modified surveillance protocol involving annual duplex ultrasound (DUS) and abdominal radiography (AXR) was introduced, with CTA performed only if abnormalities were identified or DUS was undiagnostic. METHODS Prospective records were maintained on patients undergoing infra-renal EVAR at a UK, tertiary referral centre. All patients enrolled with at least one-year follow-up were reviewed. Primary outcomes identified were aneurysm rupture and aneurysm-related complications. Secondary outcomes included number of CTAs avoided and cost. RESULTS Median follow-up was 36 months (range 12-57) for 194 patients. The total number of sets of surveillance imaging was 412 of which 70 (17%) required CTA. Abnormalities were found in 30 patients, 18 confirmed by CTA. Eleven patients required secondary intervention, three initially identified by AXR, three by DUS, three by both DUS and AXR, and two by CTA following undiagnostic DUS. No patient presented with rupture or aneurysm-related complications not identified by modified surveillance. Mean annual savings were €223. CONCLUSION EVAR surveillance based on DUS and AXR is feasible and safe. The complimentary nature of AXR and DUS is demonstrated.

Comparison of fenestrated endovascular and open repair of abdominal aortic aneurysms not suitable for standard endovascular repair.

BACKGROUND Abdominal aortic aneurysms that are unsuitable for a standard endovascular repair (EVAR) could be considered for fenestrated endovascular repair (f-EVAR). The aim of this study was to conduct a risk-adjusted retrospective concurrent cohort comparison of f-EVAR and open repair for such aneurysms. METHODS All patients who underwent repair of an abdominal aortic aneurysm that was unsuitable for a standard EVAR due to inadequate neck within one institution between January 2006 and December 2010 were identified. Case notes were retrieved for clinical data, Vascular Physiological and Operative Severity Score for enUmeration of Mortality and Morbidity (V-POSSUM) score, and aneurysm morphology. Computed tomography scans were reviewed to establish aneurysm morphology. RESULTS A total of 107 patients were identified. The open surgery cohort included 54 patients (35 men) who were a median age of 72 years (interquartile range [IQR], 9.5; range, 60-86 years). The aortic cross-clamp was infrarenal in 20 patients, suprarenal or above in 21, and inter-renal in eight. Postoperatively, 63 major complications were noted in 30 patients, nine of whom required 16 reinterventions. Cumulative hospital stay of the cohort was 1170 days (median, 12; IQR, 13; range, 1-205 days) of which 234 days (median, 28; IQR, 36; range, 1-77 days) were in the intensive therapy unit (ITU). Perioperative mortality was 9.2% (n = 5), exactly as estimated by V-POSSUM. The f-EVAR cohort included 53 patients (47 men) who were a median age of 76 years (IQR, 11.50; range, 55-87 years). Two fenestrations and one scallop was the most frequent configuration (n = 31). Postoperatively, 37 major complications were noted in 18 patients, six requiring reintervention. Hospital stay was 559 days (median, 7; IQR, 4.5; range, 4-64 days), of which 31 days (median, 4; IQR, 10.5; range, 1-15 days) were in the ITU. Two patients died perioperatively (3.7%), resulting in an observed crude absolute risk reduction of 5.5% compared with open repair. The V-POSSUM estimated perioperative death in five patients (9.4%) in the f-EVAR cohort. In a hypothetic scenario of the f-EVAR cohort undergoing open repair, V-POSSUM estimated seven deaths (13.2%), resulting in an estimated risk-adjusted absolute risk reduction due to f-EVAR of 9.5%. CONCLUSIONS In this group of patients, f-EVAR reduced mortality and morbidity substantially compared with open repair and also reduced total hospital stay and ITU utilization.

Meta-analysis of the effects of statins on perioperative outcomes in vascular and endovascular surgery.

BACKGROUND Compelling evidence from large randomized trials demonstrates the salutary effects of statins on primary and secondary protection from adverse cardiovascular events in high-risk populations. Our objective was to investigate the role of perioperative statin therapy in noncardiac vascular and endovascular surgery. METHODS Electronic information sources were systematically searched to identify studies comparing outcomes after noncardiac surgical or endovascular arterial reconstruction in patients who were and were not taking statin in the perioperative or peri-interventional period. The Cochrane Collaborations tool and the Newcastle-Ottawa scale were used to assess the methodologic quality and risk of bias of the selected studies. Random-effects models were applied to calculate pooled outcome data. RESULTS Four randomized controlled trials and 20 observational cohort or case-control studies were selected for analysis. The randomized studies enrolled 675 patients, and the observational studies enrolled 22,861 patients. Statin therapy was associated with a significantly lower risk of all-cause mortality (odds ratio [OR], 0.54; 95% CI, [CI], 0.38-0.78), myocardial infarction (OR, 0.62; 95% CI, 0.45-0.87), stroke (OR, 0.51; 95% CI, 0.39-0.67), and the composite of myocardial infarction, stroke, and death (OR, 0.45; 95% CI, 0.29-0.70). No significant differences in cardiovascular mortality (OR, 0.82; 95% CI, 0.41-1.63) and the incidence of kidney injury (OR, 0.90; 95% CI, 0.58-1.39) between the groups were identified. CONCLUSIONS Our analysis demonstrated that statin therapy is beneficial in improving operative and interventional outcomes and should be considered as part of the optimization strategy for prevention of adverse cardiovascular and cerebrovascular events and death.

Can Intrasac Pressure Monitoring Reliably Predict Failure of Endovascular Aneurysm Repair

Purpose: To determine if pressure measured at a single location within aneurysm sac thrombus accurately reflects the force applied to the aneurysm wall and the risk of rupture by examining (1) if pressure is distributed uniformly within aneurysm thrombus, (2) the pressure transmission through aneurysm thrombus, and (3) the microstructural basis for pressure transmission. Methods: Pressure within aneurysm thrombus was measured by direct puncture through the aneurysm wall at 121 sites in 26 patients during open abdominal aortic aneurysm repair. Measurements were taken prior to cross clamping and compared with intrasac pressure measured at 30 sites in 6 patients without aneurysm thrombus (controls). Transmission of pressure through aneurysm thrombus was further examined ex vivo by subjecting fresh thrombus to a pressure gradient in a custom-made pressure cell. Pressure transmission was correlated with matrix density as determined by light microscopy and image analysis. Results: Mean pressure within aneurysm thrombus was higher than mean systemic pressure in 11 patients, lower in 1, and identical in 9. In 5 patients, the pressure was greater than systemic in some areas of the thrombus but less in others. Sac pressure was identical to systemic pressure at all sites in the controls. In 12 thrombus specimens (6 patients) examined in the pressure cell, pressure transmission varied significantly between specimens, correlating directly with matrix density (R2=0.747, p=0.001). Conclusions: Pressure transmission through aneurysm thrombus is variable and depends upon the microstructure of the thrombus. Pressure measured at a single location may not, therefore, accurately reflect the pressure acting on the aneurysm wall.

Defining a role for contrast-enhanced ultrasound in endovascular aneurysm repair surveillance

OBJECTIVE Endovascular aneurysm repair (EVAR) surveillance includes duplex ultrasound, abdominal radiography, and computed tomography angiography. Contrast-enhanced ultrasound (CEUS) has emerged as an additional modality whose role remains undefined. We evaluated whether a potential role for CEUS was the elucidation of unresolved issues following standard surveillance modalities. METHODS All patients undergoing EVAR at a tertiary referral center had surveillance based on plain abdominal radiograph and duplex ultrasound, with single arterial phase computed tomography angiography reserved for abnormalities or nondiagnostic imaging. In this prospective evaluation, from April 2010 to July 2011, discordance between imaging modalities or unresolved surveillance issues prompted CEUS. Cases and imaging were discussed in a multidisciplinary setting and outcomes recorded. RESULTS During the study period, 539 patients underwent EVAR surveillance, of whom 33 (6%) had CEUS for unresolved issues (median age, 79; range, 66-90; 28 male). Median follow-up after EVAR was 23 months (range, 0-132). In all cases, CEUS was able to resolve the clinical issue, resulting in secondary intervention in 10 patients (30%). The remaining patients were returned to surveillance. Within the cohort of 33 patients, the clinical issues were categorized into three groups. Group 1: Endoleak of uncertain classification (n = 27: 21 type II, four type I, two had endoleak excluded). Group 2: Significant aneurysm expansion (≥ 5 mm) without apparent endoleak (n = 4: one type II, three had endoleak excluded). Group 3: Target vessel patency following fenestrated EVAR (n = 2: patency confirmed in both). CONCLUSIONS CEUS can enhance EVAR surveillance through clarification of endoleak and target vessel patency when standard imaging modalities are not diagnostic.

Wholly endovascular repair of thoracoabdominal aneurysm.

The aim was to evaluate a wholly endovascular approach to the repair of thoracoabdominal aortic aneurysm (TAAA).

Fascial Closure Following Percutaneous Endovascular Aneurysm Repair

INTRODUCTION There are potential benefits of percutaneous over open femoral access for endovascular aneurysm repair (EVAR). Subsequent arterial closure using percutaneous devices is costly, whilst open repair risks potential wound complications and delayed discharge. The technique of fascial closure has perceived advantages but its efficacy is unclear. The aim of this study was to assess the safety and durability of fascial closure after EVAR. METHODS Patients undergoing EVAR using devices up to 24 French were considered. Exclusion criteria included morbid obesity, high bifurcation, previous surgery, inadvertent high puncture, arteries < 5 mm and surgeon preference. The primary outcome measure was immediate technical success. All patients were followed-up clinically and with duplex at one and twelve months to determine secondary complications. RESULTS Over a one-year period fascial closure of 69 common femoral arteries was attempted in 38 patients undergoing EVAR. Nine primary failures were due to haemorrhage in eight arteries and thrombosis in one artery; all had immediate, uncomplicated open revision. Of the 60 (87%) successful procedures, all had duplex surveillance at one month. Four pseudoaneurysms were identified, all treated conservatively. At one year, 61 fascial closures (88%) were imaged, four patients had died and two were lost to follow-up. Three of the pseudoaneurysms had resolved, the fourth patient had died (unrelated). No other complication attributable to fascial closure was found at either one or twelve months. CONCLUSION Fascial closure is a safe, durable and cost-effective method of arterial closure following EVAR. Success and complication rates are comparable to other techniques.