Geoffrey L. Gilling-Smith

Endotension after endovascular aneurysm repair: definition, classification, and strategies for surveillance and intervention.

In the ongoing evolution of a categorization system for endoleak, the authors propose the term endotension to define persistent or recurrent pressurization of the aortic aneurysm sac after endovascular repair. Endotension is evidence that the aneurysm remains at risk of rupture and should, therefore, be considered an indication for secondary intervention. Management strategies and a grading system for endotension are offered.

Longitudinal aneurysm shrinkage following endovascular aortic aneurysm repair: a source of intermediate and late complications.

PURPOSE To report the incidence of delayed complications following endovascular abdominal aortic aneurysm (AAA) repair and the relationship of these sequelae to morphological changes in the sac and endograft. METHODS Twenty-six AAA patients treated with Vanguard endografts had completed > or = 1-year follow-up. Postoperative angiograms and spiral computed tomographic (CT) scans with 3-dimensional reconstruction were compared to the 1-year images to determine morphological changes in the aneurysm sac and the endograft. These changes were then related to complications occurring between 1 and 12 months postoperatively in the study group. RESULTS Comparison of angiograms uncovered endograft buckling in 18 (69%) patients and acutely angled or kinked endografts in 10 (38%). Measurements from the CT scans found that undistorted endografts had a mean change in sac length of +6.6 mm. Mean sac length change in buckled endografts was -3.1 mm, while kinked endografts displayed a mean change of -6.2 mm (p < 0.002, Students t-test). Five (19%) patients, all with distorted endografts, demonstrated late (1 to 12 months) complications (4 endoleaks and 1 graft limb thrombosis) owing to component separation, distal stent migration, and acute angulation. No movement in the proximal stent was observed. Elongation of the endograft (flow line measurement) was observed in one tube graft only. CONCLUSIONS In this study, longitudinal shrinkage of the sac following endovascular aortic aneurysm repair led to buckling or kinking of the endograft within 1 year in 69% of patients. This appears to be an important source of delayed complications.

Fenestrated endovascular repair for juxtarenal aortic aneurysm.

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

Detection of Endoleak with Enhanced Ultrasound Imaging: Comparison with Biphasic Computed Tomography

Purpose: To compare unenhanced and enhanced ultrasound imaging to biphasic computed tomography (CT) in the detection of endoleak after endovascular abdominal aortic aneurysm (AAA) repair. Methods: Fifty-three patients (44 men; mean age 70 years) were examined during 96 follow-up visits after endovascular AAA repair. All patients had color Doppler and power Doppler ultrasound studies performed before and after the administration of an ultrasound contrast agent. Biphasic (arterial and delayed) CT was performed on the same day, and the ultrasound and CT studies were independently scored to record the presence or absence of endoleak and the level of confidence in the observation. Results: The sensitivity of the ultrasound techniques to detect endoleak improved with the use of ultrasound contrast media, ranging from a low of 12% with unenhanced color Doppler to 50% with enhanced power Doppler. However, the enhanced power Doppler failed to detect 9 type II endoleaks identified by CT (86% negative predictive value for endoleak). There were only 2 graft-related endoleaks in the study; one was diagnosed from the ultrasound image, but the other had nondiagnostic ultrasound scans because of poor views. Conclusions: Ultrasound scanning with or without contrast enhancement was not as reliable as CT in diagnosing type II endoleak. CT imaging remains our surveillance modality of choice.

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.

Use of contrast-enhanced ultrasound in follow-up after endovascular aortic aneurysm repair

PURPOSE To investigate the use of contrast-enhanced ultrasound in the detection of endoleak after endovascular repair of abdominal aortic aneurysm. MATERIALS AND METHODS Eighteen patients underwent follow-up on 20 occasions after endovascular aortic aneurysm repair by arterial-phase contrast-enhanced spiral computed tomography (CT). All patients had unenhanced color Doppler ultrasound and Levovist-enhanced ultrasound on the same day. The ultrasound examinations were reported in a manner that was blind to the CT results. CT was regarded as the gold standard for the purposes of the study. RESULTS There were three endoleaks shown by CT. Unenhanced ultrasound detected only one endoleak (sensitivity, 33%). Levovist-enhanced ultrasound detected all three endoleaks (sensitivity, 100%). Levovist-enhanced ultrasound indicated an additional six endoleaks that were not confirmed by CT (specificity, 67%; positive predictive value, 33%). In one of these six cases, the aneurysm increased in size, which indicates a likelihood of endoleak. Two of the remaining false-positive results occurred in patients known to have a distal implantation leak at completion angiography. CONCLUSION In this small group of patients, contrast-enhanced ultrasound appears to be a reliable screening test for endoleak. The false-positive results with enhanced ultrasound may be due to the failure of CT to detect slow flow collateral pathways. Although the number of patients in this study is small, enhanced ultrasound may be more reliable than CT in detecting endoleak.

Aortic Side Branch Embolization before Endovascular Aneurysm Repair: Incidence of Type II Endoleak

PURPOSE To assess the feasibility of embolization of aortic side branches and its impact on the incidence of type II endoleak after endovascular aneurysm repair. MATERIALS AND METHODS Endovascular aneurysm repair was performed in 74 patients. Aortic side branch vessels were evaluated on the preoperative angiogram and computed tomography (CT) and, where embolization of lumbar and inferior mesenteric vessels was considered technically possible, this was attempted prior to endovascular repair. Follow-up CT was used to assess the presence of type II endoleak. RESULTS Seventy-two patients were followed up for longer than 1 month. Embolization was attempted in 25 cases, successfully in 10, with partial success in 11, and failure in four. Twenty patients with successful or partly successful preoperative embolization were discharged and followed-up. Four (20%) had demonstrable type II endoleak during follow-up, with two of these persisting at latest follow-up. Of 43 patients without previous embolization, there were 10 (23.3%) type II endoleaks during the follow-up period, four of these persisting. In cases with type II endoleak, mean sac diameter change was -0.5 mm in the cases with previous embolization and +3.1 mm without. The mean period to onset of type II endoleak was 6.9 months without, and 15.3 months with, previous embolization. CONCLUSION Although the cohort size is below a level that would confer significance, the trend of these findings is such as to suggest a lack of influence of aortic side branch embolization on the incidence of type II endoleak during the follow-up period.

Late complications after ligation and bypass for popliteal aneurysm

Ligation and bypass is standard treatment for popliteal aneurysm. This technique does not abolish collateral circulation to the aneurysm, which may continue to expand and/or rupture. This study assessed whether complete thrombosis of the aneurysm sac occurs after operation and examined the long‐term clinical outcome.

Adjunctive Iliac Stents Reduce the Risk of Stent-Graft Limb Occlusion following Endovascular Aneurysm Repair with the Zenith Stent-Graft:

Purpose: To determine whether the introduction of a policy of adjunctive stent insertion based on preoperative CT assessment or completion angiography reduced the incidence of limb occlusion after stent-graft implantation for endovascular aneurysm repair (EVAR). Methods: A tertiary referral units endovascular database was retrospectively interrogated to compare the incidence of endograft limb occlusion in Zenith grafts following the introduction of a policy of selective adjunctive stent insertion. Group A included 288 limbs at risk in 146 patients (134 men; mean age 74±8 years) treated prior to August 2005 in whom adjunctive stents were inserted on an ad hoc basis only. Group B included 293 limbs at risk in 149 patients (127 men; mean age 76±7 years) treated after this date in whom a more aggressive adjunctive stenting strategy was adopted. Kaplan-Meier analysis was employed to compare outcomes. Results: In total, 295 patients underwent EVAR involving 581 iliac vessels, of which 11 (1.8%) occluded at a median of 24 months (0–27). Of 65 limbs extended into the external iliac segment, 5 (7.6%) subsequently occluded; in the remaining 516 limbs, there were 6 (1.1%) occlusions (p=0.004). Across the study group, 38 (6.5%) adjunctive stents were deployed in limbs deemed at risk; 1 (2.6%) of these occluded. In the remaining 543 unstented limbs, 10 (1.8%) occlusions occurred (p=0.15). There were 11 occlusions in group A, in which 5 (1.7%) adjunctive stents had been deployed, but none in group B, which had received 33 (11.2%) stents (p<0.0001). Kaplan-Meier survival curves identified primary patency rates at 36 months of 96% and 100%, respectively (p=0.001). Conclusion: Adjunctive stenting significantly reduces the risk of postoperative stent-graft limb occlusion without obvious compromise to the aneurysm repair.

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.