Endoleakage after stent-graft treatment of abdominal aneurysm: implications on pressure and imaging--an in vitro study

Intra-aneurysm sac pressure measurements after endovascular aneurysm repair: differences between shrinking, unchanged, and expanding aneurysms with and without endoleaks

OBJECTIVE

Our objective was to study intra-aneurysm pressure after endovascular aneurysm repair (EVAR) in shrinking, unchanged, and expanding abdominal aortic aneurysms (AAAs) with and without endoleaks.

METHODS

Direct intra-aneurysm sac pressure measurement (DISP) by percutaneous translumbar puncture of the AAA under fluoroscopic guidance was performed 46 times during the follow-up of 37 patients (30 men; median age, 73 years [range, 58-82 years]; AAA diameter: median, 60 mm [range, 48-84 mm]). Three patients were included in two different groups because DISP was performed more than once with different indications. Tip-pressure sensors mounted on 0.014-inch guidewires were used for simultaneous measurement of systemic and AAA sac pressures. Mean pressure index (MPI) was calculated as the percentage of mean intra-aneurysm pressure relative to the simultaneous mean intra-aortic pressure.

RESULTS

Median MPI was 19% in shrinking (11 patients), 30% in unchanged (10 patients), and 59% in expanding (9 patients) aneurysms without endoleaks. Pulse pressure was also higher in expanding (10 mm Hg) compared with shrinking (2 mm Hg; P <.0001) AAAs. Four of the nine patients with expanding AAAs underwent five repeated DISPs later in the follow-up, and MPIs were consistently elevated. Seven of the 10 patients with unchanged AAAs without endoleaks underwent further computed tomography follow-up after DISP; 2 expanded (MPI, 47%-63%), 4 shrank (MPI, 21%-30%), and 1 remained unchanged (MPI, 14%). Type II endoleaks (6 patients, 7 DISPs) were associated with wide range of MPI (22%-92%). Successful endoleak embolization (n = 4) resulted in pressure reduction.

CONCLUSIONS

Intra-aneurysm sac pressure measurement is an important adjunctive for EVAR evaluation, possibly allowing early detection of failures. High pressure is associated with AAA expansion and low pressure with shrinkage. Type II endoleaks can be responsible for AAA pressurization, and successful embolization appears to result in pressure reduction.

Endovascular treatment of abdominal aortic aneurysm

BACKGROUND

Endovascular repair of abdominal aortic aneurysm has become widely used. Supporters claim high success rates, few complications and a dramatically reduced hospital stay. However, endoleak, endotension and reports of endoprosthesis rupture are causes of concern.

METHODS

A Medline search was undertaken to identify articles on endovascular repair of abdominal aortic aneurysm. Additional papers were identified by manual scanning of the references from key articles.

RESULTS AND CONCLUSION

Endoleak is a potentially serious complication of the endovascular technique and occurs in a significant proportion of patients. It is still not possible to judge whether the presence of an endoleak alone signifies failure of treatment, and the long-term durability of prosthetic covered stents is unknown. However, endovascular repair does appear to confer a degree of protection from rupture although patients must be advised of the need for life-long imaging surveillance and, perhaps, further intervention.

Variability of maximal aortic aneurysm diameter measurements on CT scan: significance and methods to minimize

OBJECTIVES

We noted substantial differences when measuring repeatedly the same abdominal aortic aneurysm (AAA) on the same computed tomography (CT) scan. This study quantitated this variability, and methods to minimize it were developed.

METHODS

The CT maximal diameter of 25 AAAs was measured by eight experienced observers, including six vascular surgeons and two radiologists, using two methods: an unstandardized protocol, and a standardized protocol using fine calipers to carefully measure the largest diameter perpendicular to the estimated aneurysm centerline, from outer aneurysm wall to outer wall. The average measurement difference between observers was calculated for each method. The average difference between each observer's measurement and the official radiology report value was also calculated. Agreement between the two measurement methods was assessed with Bland-Altman plots.

RESULTS

The difference in maximal diameter measurements between each observer averaged 4.0 +/- 5.1 mm (range, 0.0-35.0 mm) with the unstandardized method. The mean measurement difference with the standardized protocol was significantly lower, and averaged 2.8 +/- 4.4 mm (range, 0.0-26.0 mm; P<.05). Measurements taken from the official radiology report differed from each of the observer's standardized measurement by an average of 5.0 +/- 6.3 mm (range, 0.0-28.0 mm). This difference was similar for both the unstandardized and standardized methods. Bland-Altman plots confirmed the wide variation of the maximal diameter measurements when the unstandardized method was compared with the standardized method (95% confidence interval, -9-9 mm).

CONCLUSIONS

Routine CT maximal diameter measurement of AAAs can have substantial interobserver variability. Standardized measurement protocols can decrease, but not eliminate, this measurement variability. Thus apparent size changes based on CT measurements may represent measurement artifact rather than actual aneurysm growth or shrinkage, particularly when a standardized system is not used.

Is a Type II Endoleak after EVAR a Harbinger of Risk? Causes and Outcome of Open Conversion and Aneurysm Rupture during Follow-up

OBJECTIVE

There is still debate whether type II endoleaks represent a risk for the patient after EVAR. Treatment policies vary from fairly conservative to active intervention. In this analysis risk factors for type II endoleak and adverse events during follow-up were assessed. In addition, risk factors and causes for conversion to open repair and for rupture post-EVAR were studied.

METHODS

The data of 3595 patients, who underwent operation between 1996 and 2002 in 114 European institutions that collaborated in the EUROSTAR Registry, were assessed. To accurately assess the influence of type II endoleaks patients with type I, III and combined endoleaks were excluded from the present study cohort.

RESULTS

A combined adverse outcome event consisting of aneurysmal growth, transfemoral reintervention, and transabdominal secondary procedures (including laparoscopic branch vessel clipping) occurred in 55% in patients with type II endoleak at 3 years, compared to 15% in patients without any endoleak (p<0.0001). Conversion to open repair or post-EVAR rupture was not significantly associated with type II endoleaks. An independent association of device migration and expansion of the aneurysm with late conversion was observed. The cumulative incidence of aneurysm rupture at 3 years of follow-up was 1.2% for an annual rate of 0.4%. Variables that significantly and independently correlated with rupture were size of the aneurysm at preoperative measurement and device migration during follow-up.

CONCLUSION

Endoleak type II may not be harmless as it was more frequently associated with enlargement of the aneurysm and reinterventions. Large aneurysms and migration of the device were the main risk factors for rupture. The clinical implications of these findings may involve more frequent surveillance visits for patients with type II endoleak. Aneurysm expansion is a clear indication for reintervention. Patients with large aneurysms, 65 mm or larger, may also benefit from a more comprehensive surveillance schedule.

Endotension as a Result of Pressure Transmission through the Graft following Endovascular Aneurysm Repair—An In vitro Study

BACKGROUND

endovascular aneurysm repair (EVAR) significantly reduces, but does not abolish aneurysm sac pressure, possibly because of trans-fabric transmission.

OBJECTIVE

to investigate how blood pressure is transmitted through different types of grafts into the aneurysm sac.

DESIGN

experimental study, in vitro.

METHODS

a latex aneurysm was inserted into an in vitro circulation model. The systemic mean pressure (SPmean) was varied from 50 to 120 mmHg. The grafts used for aneurysm exclusion were: thin wall polyethylene (PE), thick wall polyethylene (PE) and thin wall ePTFE. Mean aneurysm sac pressure (ASPmean) was measured, as was pulse pressure (ASPpulse).

RESULTS

at an SPmean of 70 mmHg, the ASPmean was 34 +/- 0.8 mmHg (polyethylene knitted, thick wall), 30 +/- 1.0 mmHg (polyethylene woven, thin wall), and 17 +/- 0.6 mmHg (thin wall ePTFE). The ASPmean increased with SPmean, the relationship depending on the graft material. Stiffer grafts were associated with lower ASPmean and ASPpulse (p<0.001).

CONCLUSIONS

the relationship between aneurysm sac mean pressure and systemic pressure (SP) depends on the graft material. These data highlights the need for further studies regarding endotension.

Secondary intervention following endovascular repair of abdominal aortic aneurysm: A single centre experience

AIMS

We aim from a review of our early and late experience of secondary intervention for technical failures, to examine and describe the impact of endovascular and open interventions.

METHODS

108 Abdominal Aortic Aneurysms (AAAs) repaired endoluminally between 1995-2001 were analysed. In our early experience, during 1995/96 home made pre-expanded polytetrafluoroethylene grafts fixed with Palmaz stents were used (n = 26). In our later experience, 1997/2001 Talent (n = 70) or Zenith endografts (n = 12) were used. All cases underwent spiral CT at 5 days and 6 monthly intervals post-op. Angiography was performed when further intervention was intended. All technical failures requiring intervention or not were studied.

RESULTS

There were 28 (26%) technical failures identified of which 14 of 26 (54%) occurred in our early experience, and 14 of 86 (16%) occurred in our later experience (p < 0.05). Eleven in all required open conversion at the time of endovascular repair. Our study cohort were the remaining 17 cases requiring secondary intervention, seven were from our early experience and 10 from our later experience. There were 12 endoleaks, including two as a result of graft migration, two graft occlusions, two graft distortions and one graft infection. Overall 10 (66%) technical failures were treated by endoluminal repair and seven (34%) by open methods. However, in our later experience significantly more endoluminal techniques (80%) were used (p < 0.05).

CONCLUSIONS

Technical failure rates were significantly higher in our earlier experience. Open repair, which was a feature of our early experience, has been avoided over the final 3 years. Instead, endoluminal techniques were used without further morbidity or mortality. Aneurysm rupture has not so far been experienced in this experience.

Endoleaks after Endovascular Repair of Abdominal Aortic Aneurysms

Endovascular repair of abdominal aortic aneurysms shows promising initial results. Endoleaks represent one of the unique causes of endovascular repair failure not seen with traditional abdominal aortic aneurysm repair. Endoleaks occur when there is blood flow outside the stent-graft lumen but within the aneurysm sac. They can be difficult to diagnose and treat, and their management is a source of continued controversy. This review further defines endoleaks and the clinical challenges that they create. Current methods for endoleak detection, classification, and management are reviewed.

Technique and results of transfemoral superselective coil embolization of type II lumbar endoleak

OBJECTIVE

This study was undertaken to describe the technique of transfemoral superselective coil embolization of type II endoleak and its influence on abdominal aortic aneurysm diameter.

METHODS

Over 23 months, 104 aortic stent grafts were deployed to exclude abdominal aortic aneurysms, at an academic medical center. Increase in aneurysm diameter and perigraft findings on contrast material-enhanced computed tomography scans prompted arteriography. Procedures were performed solely by vascular surgeons in a surgical angiography suite. In 7 patients aneurysm access was via the iliolumbar branches of the internal iliac artery, and in 1 patient aneurysm access was via the inferior mesenteric artery through the arc of Riolan from the superior mesenteric artery. Coaxial catheters were placed to gain access to the aneurysm (8F to 5F to 3F, or 5F to 3F). A 3F Tracker18 was the most distal catheter through which an assortment of 0.018 microcoils were deployed within the aneurysm, and the origin of the feeding vessels when possible.

RESULTS

Aneurysm diameter increased 0.48 +/- 0.2 cm over 10.8 +/- 5 months before superselective coil embolization. In 6 of 8 patients superselective coil embolization embolization resulted in a mean decrease in aneurysm diameter of 1.3 +/- 1.2 cm over 9 +/- 3.2 months. Failure was presumed due to inability to reach the aneurysm sac in 1 patient and was associated with oral anticoagulation in 1 other patient.

CONCLUSION

Proper identification of the source of type II endoleak and its complete occlusion, combined with aneurysm sac coiling, may result in prompt decrease in aneurysm size.

Distribution of sac pressure in an experimental aneurysm model after endovascular repair: the effect of endoleak types I and II

PURPOSE

To study in an experimental aneurysm model the differential distribution of strain/pressure (S/P) on the aneurysm wall before and after endograft exclusion and in the presence of individual type I and type II endoleaks.

METHODS

Two tapered elliptical Gore-Tex patches were sutured to an anterior and posterior longitudinal arteriotomy of an 8-mm Gore-Tex tube graft, thus creating a fusiform aneurysm. Two S/P transducers were placed at the proximal sac adjacent to the proximal neck, 2 at the site of the widest sac diameter, and 2 at the sac adjacent to the distal neck. The aneurysm, which was connected to a pulsatile pump system, was excluded using a 10-mm endograft. Type I and type II endoleaks were created and tested individually. S/P measurements were obtained at systemic systolic pressures (BP) of 80, 110, and 150 mmHg. Thrombosis of the sac contents was induced by injection of thrombin and calcium in the sac. Angiography was used to verify presence or absence of flow in the sac.

RESULTS

Aneurysm exclusion resulted in significant S/P reductions at all 3 BP levels versus prior to exclusion (p<0.05). Thrombus in the sac did not alter S/P in the excluded sac (p>0.05 for all 3 BP levels). In the presence of a proximal type I endoleak, S/P distribution was not uniform, and S/P at the proximal neck was close to S/P prior to exclusion (p>0.05 no graft versus type I endoleak for all 3 BP levels). This was also true in the presence of thrombus. With a type II endoleak, S/P was more evenly distributed and was not significantly elevated compared to the pressure without an endoleak (p>0.05, graft versus type II endoleak for all 3 BP levels). Thrombus had no effect on intrasac S/P with a type II endoleak. Intrasac S/P was significantly higher in the presence of a type I endoleak compared to a type II endoleak when BP=150 mmHg (p=0.008).

CONCLUSIONS

Endovascular exclusion of an aneurysm results in uniform S/P reduction in the aneurysm sac. Type I endoleak, but not type II endoleak, results in significantly higher S/P in an area of the sac adjacent to the proximal neck. Thrombus does not result in significantly different S/P distribution in the aneurysm sac.

The significance and management of different types of endoleaks

Development of endovascular abdominal aortic aneurysm repair (EVAR) has been accompanied by previously unencountered complications. The most challenging but least understood of these complications is the incomplete seal of the endovascular graft (endoleak), a phenomenon that has a variety of causes. An important consequence of endoleakage may be persistent pressurization of the aneurysm sac, which may ultimately lead to post-EVAR rupture. Data of 110 European centers were recorded in a central database (EUROSTAR). Patient, anatomic characteristics, and operative and device details were correlated with the occurrence of different types of endoleaks. Outcome events during follow-up, particularly expansion of the aneurysm, incidence of conversion to open repair, and post-EVAR rupture were assessed in the different categories of endoleaks and in a group of patients without any endoleak. Type I and III endoleak were associated with an increased frequency of open conversions or risk of rupture of the aneurysm. Device-related endoleaks also correlated with an increased need for secondary interventions. These types of endoleaks need to be treated without delay, and when no other possibilities are present, an open conversion to avert the risk of rupture should be considered. Type II endoleaks do not pose an indication for urgent treatment. However, they may not be harmless, because there was a frequent association with enlargement of aneurysm and reinterventions. Our findings suggest that more frequent surveillance examinations are indicated than in patients without collateral endoleak. The indication for intervention is primarily dictated by documented expansion of the aneurysm.

Modeling endoleaks and collateral reperfusion following endovascular AAA exclusion

PURPOSE

To investigate the effect on intrasac pressure of stent-graft deployment within a life-size silicone rubber model of an abdominal aortic aneurysm (AAA) maintained under physiological conditions of pressure and flow.

METHODS

A commercial bifurcated device with the polyester fabric preclotted with gelatin was deployed in the AAA model. A pump system generated physiological flow. Mean and pulse aortic and intrasac pressures were measured simultaneously using pressure transducers. To simulate a type I endoleak, plastic tubing was placed between the aortic wall and the stent-graft at the proximal anchoring site. Type II endoleak was simulated by means of side branches with set inflow and outflow pressures and perfusion rates. Type IV endoleak was replicated by removal of gelatin from the graft fabric.

RESULTS

With no endoleak, the coated graft reduced the mean and pulse sac pressures to negligible values. When a type I endoleak was present, mean sac pressure reached a value similar to mean aortic pressure. When net flow through the sac due to a type II endoleak was present, mean sac pressure was a function of the inlet pressure, while pulse pressure in the sac was dependent on both inlet and outlet pressures. As perfusion rates increased, both mean and pulse sac pressures decreased. When there was no outflow, mean sac pressure was similar to mean aortic pressure. In the presence of both type I and type II endoleaks, mean sac pressure reached mean aortic pressure when the net perfusion rate was low.

CONCLUSIONS

In vitro studies are useful in gaining an understanding of the impact of different types of endoleaks, in isolation and in combination, on intrasac pressure after aortic stent-graft deployment.

Aortic side branch perfusion alone does not account for high intra-sac pressure after endovascular repair (EVAR) in the absence of graft-related endoleak

OBJECTIVE

to examine the effect of stent-graft deployment on pressure within an aneurysm sac and to investigate the potential sources of intra-sac pressure.

MATERIAL AND METHODS

intra-sac pressure was monitored during and immediately after endovascular repair via an indwelling catheter. Intra-sac pressure was also monitored during conventional open repair and was compared with the pressure measured within patent lumbar and inferior mesenteric side-branches, both before and after restoration of iliac arterial blood flow. Intra-sac and side-branch pressures were recorded and expressed as ratios of simultaneously measured radial artery pressure.

RESULTS

in the absence of a graft-related endoleak (23/25 patients), endovascular repair resulted in a significant reduction in intra-sac pulse pressure (median ratio 0.31 IQR 0.10-0.46). There was no corresponding reduction in mean intra-sac pressure (median ratio 0.91; IQR 0.83-1.00). Application of clamps at conventional open repair resulted in a fall in both intra-sac pressure (median ratio 0.39, IQR 0.32-0.64) and pressure within side-branches (median ratio 0.45, IQR 0.33-0.64). Restoration of iliac blood flow resulted in a modest recovery of the side-branch pressure (median ratio 0.63, IQR 0.57-0.81), which nonetheless remained significantly less than the intra-sac pressure recorded after EVAR (p=0.01).

CONCLUSION

reperfusion of the aneurysm sac through patent side-branches seems insufficient to account for persistent pressurisation of the aneurysm after endovascular repair. This finding supports the hypothesis that pressure may be transmitted directly through stent-graft fabric.

Significance of endotension, endoleak, and aneurysm pulsatility after endovascular repair

OBJECTIVE

The lack of aneurysm pulsatility after endovascular aneurysm repair (EVAR) is deemed by some an important guide to the effectiveness of exclusion. However, factors that contribute to aneurysm pulsatility after EVAR have not been elucidated. This study quantitatively analyzed the effects of systemic pressure, aneurysm sac pressure, endoleak, branch outflow from aneurysm sac, and intra-sac thrombus on aneurysm pulsatility after EVAR.

METHODS

In an ex vivo model, an artificial aneurysm sac was incorporated within a mock circulation comprised of rubber tubing and a pulsatile pump. The aneurysm sac was then completely excluded from the circulatory circuit with two types of stent-grafts, ie, supported and unsupported, and heparinized canine blood was circulated. Systemic circulation and aneurysm sac pressure was recorded in the absence and presence of endoleaks, and simulated open and closed lumbar branch outflow from the aneurysm sac. The aneurysm sac was then filled with organized human thrombus, and all pressure measurements were repeated. Two observers blinded to the above-mentioned variables independently evaluated aneurysm sac pulsatility with palpation in five separate experiments. Analysis of variance was performed, with significance accepted at P =.05.

RESULTS

Systemic pressure was simulated in the artificial circulation to range from 100/60 to 180/60 mm Hg. Regardless of the simulated lumbar branch outflow from the aneurysm, sac pressure was directly related to the presence of endoleak (P <.001). Aneurysm sac pulsatility was present only when the lumbar branch outflow was patent and not dependent on sac pressures. Aneurysm sac thrombosis or type of stent-graft did not influence sac pressure and pulsatility.

CONCLUSIONS

In this model, after EVAR pulsatility depends on aneurysm sac outflow, regardless of endoleak, sac thrombosis, sac pressure, or stent-graft. Furthermore, persistent pulsatility does not predict systemic intra-sac pressure, nor does lack of pulsatility reflect freedom of the aneurysm sac from systemic pressurization. This ex vivo model suggests that aneurysm pulsatility is an unreliable guide for predicting aneurysm sac pressurization after EVAR. Other diagnostic methods must be used to assess successful aneurysm exclusion.

Preoperative embolization of collateral side branches: a valid means to reduce type II endoleaks after endovascular AAA repair

PURPOSE

To report the results of preprocedural embolization of collateral branches arising from abdominal aortic aneurysms (AAA) scheduled for endovascular repair.

METHODS

Twenty-three consecutive AAA patients (all men; mean age 73 years, range 56-82) had coil embolization of patent lumbar and inferior mesenteric arteries (IMA) in a staged procedure prior to endovascular repair. Embolization with microcoils was attempted in 37 of the 52 identified lumbar arteries and 14 of 15 inferior mesenteric arteries. Follow-up included biplanar abdominal radiography, spiral computed tomography, and duplex ultrasonography at 1, 30, 90, and 180 days after the stent-graft procedure and at 6-month intervals thereafter.

RESULTS

Successful embolization was obtained in 24 (65%) of lumbar arteries, while all 14 (100%) IMAs were occluded with coils. No complication was associated with embolotherapy. Over a mean 17-month follow-up of 22 patients (1 intraoperative death), there was only 1 (4.5%) type II endoleak from a patent lumbar artery, with no sac expansion after 2 years. There were 4 (18%) type I and 1 (4.5%) type III endoleaks.

CONCLUSIONS

The embolization of side branches arising from an infrarenal aortic aneurysm before endovascular repair is feasible, with a high success rate; this maneuver may play a relevant role in reducing the rate of type II endoleak, improving long-term outcome.

Contrast-enhanced ultrasound imaging for aortic stent-graft surveillance

PURPOSE

To compare unenhanced and enhanced ultrasound imaging to computed tomographic angiography (CTA) or magnetic resonance angiography (MRA) for surveillance of aortic endografts.

METHODS

Thirty consecutive patients (29 men; mean age 69 years, range 50-82) who underwent endovascular aortic aneurysm repair agreed to participate in a follow-up program. Patients underwent CTA (26/30) or MRA (4/30), plain abdominal radiography, and unenhanced and enhanced ultrasound examinations at 3, 12, and 24 months to evaluate aneurysm diameter, endoleaks, and graft patency. The accuracy of ultrasound was compared with CTA or MRA as the reference standards.

RESULTS

Twenty-six patients reached the 24-month assessment (mean follow-up 30 months, range 6-60). All endoleaks detected by CTA or MRA were confirmed by enhanced ultrasound; the aneurysm diameter in these patients remained unchanged or increased. In patients without endoleaks on any imaging method, the sac diameter remained unchanged or decreased. Endoleaks disclosed by enhanced ultrasound alone, all type II, numbered 16 at 3 months, 6 at 12 months, and 3 at 24 months. In this group, the aneurysm diameter remained unchanged or increased. Enhanced ultrasound yielded 100% sensitivity in detecting endoleaks, but compared with CTA and MRA, all endoleaks detected by enhanced ultrasound alone were false positives (mean specificity 65%). Nevertheless, because changes in the postoperative aneurysm diameter were similar in patients with endoleaks detectable on CTA/MRA and on enhanced ultrasound ("true positives") and in those with endoleaks detectable only on enhanced ultrasound ("false positives"), some endoleaks were possibly "true positive" results.

CONCLUSIONS

Enhanced ultrasound is a useful method in the long-term surveillance of endovascular aortic aneurysm repairs, possibly in association with CTA or MRA. Enhanced ultrasound also seems able to identify endoleaks missed by other imaging techniques, but this conclusion awaits further investigation.

Comparison of laparoscopic aortic clamps in a pulsatile circulation model

PURPOSE

This study was designed to evaluate the fatigue characteristics and the safety and effectiveness of laparoscopic aortic clamps in a pulsatile circulation model.

METHODS

A heart-lung machine was used to create a pulsatile circulation model with bovine aortas resembling the vessels being cross-clamped. Four different models (A-D) of laparoscopic aortic clamps were investigated, and three identical probes of each model underwent testing. Preliminary examinations were conducted to define the size and thickness of the bovine aortas that would allow effective cross-clamping and to detect gross material or functional deficits of the clamps. Then, the instruments were placed in the circulation model, which was set at a frequency of 82/min and a pressure of 200/120 mm Hg. Each clamp was subjected to these conditions for 120 hours and was opened and closed 40 times to stimulate real-life conditions. Clamping failures and mechanical defects were recorded, and the clamp parts were afterward examined with an electron microscope.

RESULTS

Two clamp models had to be eliminated from the study after the preliminary examinations. All three probes of model B displayed mechanical defects after a few applications. All probes of model D were excluded because none effectively occluded the aortas. All probes of model A and one probe of model C provided effective cross-clamping during the 120-hour test phase and showed no signs of mechanical failure. Two probes of model C broke after 51 and 57 hours of testing, respectively. Both times, the defect occurred during application of the clamps. The detailed analysis of all instruments after the testing, including electron microscope imaging, revealed that several construction deficits and weak points were responsible for the mechanical failures.

CONCLUSION

A surprisingly high incidence of clamping failures and mechanical deficits were encountered during the testing. Of the four clamps tested, only one (model A) seemed to be safe and effective enough for routine clinical use. These disappointing results demonstrate the need for further cooperation between vascular surgeons and instrument manufacturers to develop safe and effective laparoscopic vascular clamps.

Endotension distribution and the role of thrombus following endovascular AAA exclusion

PURPOSE

To determine the pattern of strain and pressure transmitted to an aortic aneurysm wall before and after endovascular exclusion and to evaluate the role of sac thrombus on the conduction of pressure and wall strain.

METHODS

Three canine thoracic aortas were used to create abdominal aortic aneurysms (AAA). The segments were placed on a pulsatile pump system, and 8 strain transducers were positioned in the aneurysm sac. Baseline strain/pressure (S/P) was recorded in 1 animal, then the AAA was excluded with a stent-graft. Thrombin was injected into the sac, and strain/pressure was recorded at 7 systemic pressures (35 to 120 mmHg) over 6 hours. The thrombus was replaced with fibrin glue, and S/P was recorded over 4 hours. Additional trials using whole and 50% diluted unclotted blood were performed prior to sac thrombosis. Computed tomography and angiography were performed before and after aneurysm exclusion.

RESULTS

Pressure transmitted to the aneurysm wall decreased following stent-graft placement (p<or=0.001). Strain/pressure was not distributed evenly in the sac (p<or=0.05), and varying systemic pressures did not affect this distribution. Pressures near the stent-graft were higher than those laterally (p<or=0.001) in all trials with interposed fresh thrombus and fibrin thrombus. The fibrin group had elevated baseline measurements, but correction for the elevated values did not influence the statistical significance (p<or=0.001). Blood and fibrin thrombus reduced transmitted wall pressure to a similar degree. Overall S/P in the fluid-filled nonclotted sac was significantly lower (p<or=0.001) than in the thrombus groups.

CONCLUSIONS

Endovascular AAA exclusion reduced strain and pressure conducted to the aneurysm wall, and the distribution of transmitted pressure in the excluded sac without endoleak differed regardless of the sac contents. Fresh thrombus reduced transmittedS/P in all trials at all systemic pressures, as did fibrin thrombus but in a less predictable fashion.

Imaging of aortic stent-grafts and endoleaks

Although the technical success of stent-graft implantation is established and relatively safe, data on the long-term safety and efficacy of endovascular repair are just emerging. Because several late complications of aortic stent-graft placement have been observed, life-long follow-up remains essential. Imaging methods form an integral part of every stage of endovascular aortic aneurysm repair. The current imaging strategy should include initial plain films, CT angiography, and color-coded Duplex sonography. Plain films are an excellent means to detect migration, angulation, kinking, and structural changes of the stent mesh, including material fatigue, at follow-up. Helical CT angiography is considered a potentially revolutionary method for the noninvasive complete postprocedural assessment of aortic sten-grafting. Current data justify the use of biphasic C angiography as the postprocedural imaging technique of choice in most patients [118]. Ultrasound offers the advantages of low cost and lack of radiation exposure. High-quality ultrasound reliably excludes endoleaks in patients after stent-grafting of AAAs. There is a substantial variability, however, in measuring the diameter of aneurysm sacs; thus, confirmation using an alternative study is prudent in cases that demonstrate a significant change in size during follow-up. MR angiography serves as an attractive alternative to CT angiography in patients with impaired renal function or known allergic reaction to iodinated contrast media. With current techniques, the visualization of aortic stent-grafts (with the exception of stainless-steel-based devices) is sufficient with MR angiography. There is evidence that MR imaging is superior to CT angiography in detecting small type 2 endoleaks or for excluding retrograde perfusion in patients with suspected endotension. The role of diagnostic catheter angiography is limited to assessment of vascular pathways in equivocal cases or for suspected endotension. Currently, a consensus view about postprocedural management after aortic stent-graft implantation is lacking. The authors propose performing a baseline CT angiography at discharge and a biphasic CT angiography and Duplex ultrasound scan at three months. In patients with no evidence of an endoleak, CT angiography, plain film and Duplex sonography (abdomen) should be repeated every year after endovascular repair. If an endoleak is present at follow-up, immediate appropriate treatment should be initiated.

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.

Potential impact of therapeutic warfarin treatment on type II endoleaks and sac shrinkage rates on midterm follow-up examination

OBJECTIVE

Successful endovascular aortic aneurysm repair depends on exclusion and spontaneous thrombosis of the aneurysm sac. The need for chronic postoperative anticoagulation therapy could limit the applicability of this technology with delay or prevention of sac thrombosis resulting in endoleak formation and altered remodeling of the aneurysm sac. The purpose of this study was the determination of whether chronic therapeutic anticoagulation therapy with warfarin was associated with an increased incidence rate of early or delayed postoperative endoleaks or altered rates of reduction in aneurysm sac maximum diameter.

METHODS

Two hundred thirty-two consecutive patients underwent abdominal aortic endografting during a 32-month period. The data were recorded prospectively with a current mean follow-up period of 18 months. The patients with endoleaks identified with 30-day postoperative computed tomographic scan angiograms subsequently underwent selective arteriography to characterize the source. The patients who underwent chronic warfarin therapy that resulted in a therapeutic internationalized normalized ratio comprised the study group. The control group was defined as all the patients with healthy coagulation profiles.

RESULTS

Thirty-six patients (15%) were undergoing warfarin therapy after surgery, and their conditions were chronically maintained with a therapeutic international normalized ratio. Forty-three patients (18%) had endoleaks on 30-day computed tomographic scan angiographic results. There were 39 patients with type II endoleaks and four patients with type I endoleaks. None of the type I endoleaks occurred in patients who were undergoing warfarin therapy, and all endoleaks were repaired with either proximal or distal covered extensions. At 30 days, seven patients (19.4%) undergoing chronic warfarin therapy had type II endoleaks as compared with 36 controls (18.4%; P =.798). Four patients had delayed type II endoleaks develop, two in the control group and two in the warfarin group (P =.3). Ten control individuals (31%) had spontaneous resolution of type II endoleaks develop, whereas spontaneous endoleak thrombosis was not observed in the warfarin group (P =.33). Aneurysm sac remodeling assessed with mean percent reduction in maximum sac diameter at 12 months revealed a statistical difference between the control group (17.5%) and the warfarin group (7.6%; P =.04).

CONCLUSION

Warfarin treatment is not associated with an increase in the incidence rate of early or delayed postoperative endoleaks. However, the rate of reduction in maximum aneurysm sac diameter after aortic endografting is slower in patients who undergo therapeutic warfarin therapy at 1-year follow-up examination, a statistically significant difference from the control group. In addition, type II endoleaks may be less likely to undergo spontaneous thrombosis in patients who undergo warfarin therapy.

Evaluation of abdominal aortic aneurysm after endoluminal treatment: comparison of color Doppler sonography with biphasic helical CT

OBJECTIVE

The purpose of this study is to compare color Doppler sonography with biphasic helical CT in the evaluation of abdominal aortic aneurysms after endovascular repair.

MATERIALS AND METHODS

Fifty-five patients prospectively underwent both color Doppler sonography and helical CT within 7 days after treatment by endovascular stent-graft. Aneurysmal thrombosis, the patency of the grafts, and the presence of a leak were evaluated in all patients. When a perigraft leak was observed, an attempt was made to identify its origin and outflow vessels. Helical CT was considered the gold standard technique.

RESULTS

Helical CT revealed aneurysmal thrombosis in 33 patients and a perigraft leak in 22 patients. In five patients, helical CT detected a small perigraft leak not shown by color Doppler sonography. In three patients with suboptimal examinations, color Doppler sonography revealed a suspected perigraft leak that was not confirmed by helical CT. In these eight patients, the perigraft leak was sealed or no longer observed during follow-up. Compared with enhanced helical CT, the sensitivity and specificity of color Doppler sonography for the diagnosis of a perigraft leak were 77% and 90%, respectively. In seven other patients, helical CT was superior to color Doppler sonography in detecting the origin of the perigraft leak and the outflow vessels. Two iliac artery dissections and one distal migration of the prosthesis were revealed only by helical CT.

CONCLUSION

Although color Doppler sonography may detect substantial perigraft leaks, helical CT is superior for detecting the origin of the perigraft leak, the outflow vessels, and the detection of complications related to the procedure.

Significance of endoleaks after endovascular repair of abdominal aortic aneurysms: The EUROSTAR experience

OBJECTIVE

The purpose of this study was to assess the incidence, risk factors, and consequences of endoleaks after endovascular repair of abdominal aortic aneurysm.

METHODS

Data on 2463 patients were collected from 87 European centers and recorded in a central database. Preoperative data were compared for patients with collateral retrograde perfusion (type II) endoleak (group A), patients with device-related (type I and III) endoleaks (group B), and patients in whom no endoleak was detected (group C). Only endoleaks observed after the first postoperative month of follow-up were taken into consideration. Regression analysis was performed to investigate statistical relationships between the occurrence and type of endoleak and preoperative patient and morphologic characteristics, operative details, type of device, and experience of the operating team. In addition, postoperative changes in aneurysmal morphology, the need for secondary interventions, conversions to open repair, aneurysmal rupture, and mortality during follow-up were compared between these study groups.

RESULTS

Patients in group A had a higher prevalence of a patent inferior mesenteric artery compared with patients without endoleak. Patients in group B were treated more frequently than patients in group C by an operating team with experience of less than 30 procedures. The mean follow-up period was 15.4 months. Secondary interventions were needed in 13% of the patients. Rupture of the aneurysm during follow-up occurred in 0.52% (1/191) in group A, 3.37% (10/297) in group B, and 0.25% (5/1975) in group C. Life table analysis comparing the three study groups demonstrated a significantly higher rate of rupture in group B than in group C (P =.002). The incidence of conversion to open repair during follow-up was higher in group B than in the other two study groups (P <.01). Death was related to the aneurysm or to endovascular repair of the aneurysm in 7% of patients. Secondary outcome success, defined as absence of rupture and conversion, was significantly higher in group A and C compared with that in group B (P =.006 and P =.0001, respectively).

CONCLUSIONS

The presence of device-related endoleaks correlated with a higher risk of aneurysmal rupture and conversion compared with patients without type I or III endoleaks. Type II endoleak was not associated more often with these events. Consequently, intervention in type II endoleak should only be performed in case of increase of aneurysm size.

Noninvasive diagnosis of incomplete endovascular aneurysm repair: D-dimer assay to detect type I endoleaks and nonshrinking aneurysms

PURPOSE

To test the hypothesis that D-dimer (D-D), a cross-linked fibrin degradation product of an ongoing thrombotic event, could be a marker for incomplete aneurysm exclusion after endovascular abdominal aortic aneurysm (AAA) repair.

METHODS

In a multicenter study, 83 venous blood samples were collected from 74 AAA endograft patients and controls. Twenty subjects who were >6 months postimplantation and had evidence of an endoleak and/or an unmodified or increasing AAA sac diameter formed the test group. Controls were 10 nondiseased subjects >65 years old, 18 AAA surgical candidates, and 26 postoperative endograft patients with no endoleak and a shrinking aneurysm. Blood samples were analyzed for D-D through a latex turbidimetric immunoassay. The endograft patients were stratified into 5 clinical groups for analysis: no endoleak and decreasing sac diameter, no endoleak and increasing/unchanged sac diameter, type II endoleak and decreasing sac diameter, type II endoleak and increasing/unchanged sac diameter, and type I endoleak.

RESULTS

Individual D-D values were highly variable, but differences among clinical groups were statistically significant (p < 0.0001). D-D values did not vary significantly between patients with stable, untreated AAAs and age-matched controls (238 +/- 180 ng/mL versus 421 +/- 400 ng/mL, p > 0.05). Median D-D values increased at 4 days postoperatively (963 ng/mL versus 382 ng/mL, p > 0.05) and did not vary thereafter if there was no endoleak and the aneurysm sac decreased. D-D mean values were higher in patients with type I endoleak (1931 +/- 924 ng/mL, p < 0.005) and those with unchanged/increasing sac diameters (1272 +/- 728 ng/mL) than in cases with decreasing diameters (median 638 +/- 238 ng/mL) despite the presence of endoleak (p < 0.0005).

CONCLUSIONS

Elevated D-D may prove to be a useful marker for fixation problems after endovascular AAA repair and may help rule out type I endoleak, thus excluding patients from unnecessary invasive tests.

Diagnosis and management of type 2 endoleaks after endovascular aneurysm repair

Endovascular repair is a major treatment advance in patients with large infrarenal abdominal aortic aneurysms. Since the FDA approved two commercial devices 2.5 years ago, over 40,000 patients have undergone this procedure in the United States. Although we have learned a great deal, more than a few mysteries relating to the long-term performance of these devices remain. This results in never-ending surveillance protocols searching for graft failure and aneurysm expansion. One of the especially contentious issues is the management of type 2 endoleaks. Unlike other endoleaks that are related to problems with the graft and/or fixation, this type of leak occurs in patients with properly functioning devices. This is why so much controversy exists about whether or not these patients must be treated. Some advocate "watchful-waiting" intervention only when there is aneurysm expansion. Others routinely treat patients with type 2 endoleaks in an attempt to prevent expansion. As with most controversial topics, if you look carefully, there is more agreement than disagreement between the two groups. In this review, we will first describe the methods used for endoleak diagnosis and treatment. We will then review our current endoleak treatment algorithm and explain its rationale for use.

Intra-aneurysmal pressure after incomplete endovascular exclusion

PURPOSE

An endoleak results from the incomplete endovascular exclusion of an aneurysm. We developed an experimental model to analyze hemodynamic changes within the aneurysm sac in the presence of an endoleak, with and without a simulated open collateral branch.

METHODS

With a latex aneurysm model connected to a pulsatile pump, pressures were measured simultaneously within the system (systemic pressure) and the aneurysm sac (intrasac pressure). The experiments were performed without endoleak (control group) and after creating a 3.5-mm (group 1), 4.5-mm (group 2), and 6-mm (group 3) diameter orifice in the endograft, simulating an endoleak. Pressures were also registered with and without a patent aneurysm side branch.

RESULTS

In each endoleak group, the intrasac diastolic pressure (DP) and mean pressure (MP) were significantly higher than the systemic DP and MP (P =.01, P =.006, and P =.001, respectively), although the pressure curve was damped. The presence of an open side branch significantly reduced the intrasac DP and MP.

CONCLUSION

In this model, intrasac pressures were significantly higher than systemic pressures in the presence of all endoleaks, even the smallest ones. Intrasac pressures higher than systemic pressure may pose a high risk for aneurysm rupture. Although patent side branches significantly reduce these pressures, the aggressive management of an endoleak should be pursued.

Unusual case of AneuRx stent-graft failure two years after AAA exclusion

PURPOSE

To present a case of type-III endoleak due to separation of modular components and suture breakage after abdominal aortic aneurysm (AAA) repair with the AneuRx stent-graft.

CASE REPORT

A 58-year-old man with a 78-mm AAA underwent successful aneurysm exclusion with an AneuRx stent-graft in 1998. Because the bifurcated component migrated during deployment, an additional aortic cuff was deployed to extend the stent-graft proximally to just below the renal arteries. On routine evaluation with computed tomography at 2 years postimplantation, a type-III endoleak with anterior displacement of the stent-graft was discovered. Angiography revealed separation of the aortic cuff from the stent-graft body. The aneurysm, which had decreased to 70 mm at 6 months, had enlarged to 80 mm in diameter. The patient underwent surgical AAA repair with removal of the stent-graft. Macroscopic examination showed suture breakage and separation of the stent rings and the graft material.

CONCLUSIONS

This late complication of the AneuRx endograft underscores the need for frequent imaging surveillance in all patients undergoing endoluminal AAA repair.

Embolization of type II endoleaks after aortic stent-graft implantation: technique and immediate results

PURPOSE

We report the procedural details and immediate results of treatment of type II endoleaks after aortic stent-graft implantation.

METHODS

In a consecutive series of patients who had either Vangard (n = 53) or Talent (n = 7) aortic stent-grafts implanted, type II endoleaks were confirmed by means of angiography in 18 patients, with a mean (+/- SD) age of 69 +/- 11 years; 16 patients had Vangard stent-grafts, and two patients had Talent stent-grafts. After superselective catheterization of the feeding vessel, with 3F microcatheters, and liberal injections of vasodilators, embolization was performed with either a mixture of biologic glue and Lipiodol (n = 16) or Microcoils (n = 2).

RESULTS

The procedure was performed through the femoral artery in 16 patients and through the brachial artery in the remaining two patients. Overall, superselective catheterization and embolization were successfully undertaken in 17 (94.4%) of 18 patients. In the remaining patient, superselective catheterization proved impossible. This patient was treated with an injection of microparticles completed by means of embolization of biologic glue more proximally in an iliolumbar branch. During follow-up (mean, 13.3 months) after embolization, the aneurysm sac shrank in 13 (72.2%) of 18 patients. A new type II endoleak was diagnosed on helical computed tomography or magnetic resonance imaging in two (11.1%) of 18 patients.

CONCLUSION

Percutaneous embolization is a safe and effective technique for treatment of type II endoleaks. However, despite these initially promising results, large long-term follow-up studies will be required to confirm its efficiency.

Pressure measurements in closed aneurysmal sac during abdominal aortic aneurysm resection

PURPOSE

This study determined the relationship between closed aneurysmal sac pressure (ASP) and mean blood pressure (BP) during open abdominal aortic aneurysm (AAA) resection and evaluated the contribution of inferior mesenteric and lumbar artery blood flow to ASP after proximal and distal clamping.

METHODS

We measured ASP after proximal and distal clamping by placing an 18-gauge needle connected to a BP transducer into the excluded aneurysmal sac in 25 consecutive patients from April 1999 to August 2000. Simultaneous measurement of the mean systemic BP was also recorded. The ratio of ASP to mean BP in relation to the number of actively bleeding lumbar arteries (N-LA), diameter of the AAA (D-Cm), and volume of the thrombus in the AAA (Vol-TA) were recorded.

RESULTS

The mean ASP was 43.32 +/- 15.19 mm Hg, with an ASP to mean BP ratio of 0.47 +/- 0.15. The N-LA in the closed aneurysmal sac ranged from 0 to 6 (mean, 3.4 +/- 1.78). The D-Cm as determined by means of computed tomography (CT) scan of the aorta ranged from 5 to 8 cm in its largest anteroposterior/transverse diameter. The average Vol-TA was 6.15 +/- 4.49 mL. Inferior mesenteric artery blood flow contributed to ASP in three patients (12%). There was no correlation between ASP to mean BP ratios and the N-LA (P =.127), D-Cm (P =.882), or Vol-TA (P =.252).

CONCLUSION

Closed ASP and ASP ratios are highly variable and do not correlate with N-LA, D-Cm, or the Vol-TA.

Endotension after endovascular aneurysm repair: the Ancure experience

PURPOSE

The expansion of aneurysms after endovascular repair is a consequence of persistent sac pressure, usually resulting from an endoleak. Several authors have suggested that sac expansion can occur even in the absence of endoleak, referring to this phenomenon as endotension. This study undertakes a review of the largest US endograft trial data to better define the significance of aneurysm expansion in the absence of endoleak.

METHODS

The core laboratory imaging database from the Ancure (Guidant) endovascular graft Phase I and Phase II trials approved by the Food and Drug Administration was reviewed with attention to aneurysm size and endoleak. Aneurysm size was measured with standardized two-dimensional computed tomography (CT) scan at the area of largest initial aneurysm diameter. Endoleak was detected with CT scans, color duplex ultrasound scans, and angiography in selected cases. Patients were evaluated at baseline, 3 months, 6 months, 12 months, and every 12 months thereafter. An endograft was classified as leaking if any endoleak was detected with any modality at any time point.

RESULTS

A total of 658 patients were entered into these protocols and the data submitted to the core laboratory. A control group of 120 conventional aortic patients and a group of 62 without baseline CT data were excluded from further analysis. Of the remaining 476 patients, 144 (60 tube, 60 bifurcated, and 24 mono-iliac) were free of endoleak at all intervals and had baseline CT measurements to allow comparison. Overall, the average size decrease in this nonleaking group was 9.9 +/- 9.4 mm (range, -50.6-11.1 mm) at a mean follow-up of 23.3 months. Evaluation for overall aneurysm expansion revealed 17 patients who had an increase of 2.3 +/- 2.9 mm (range, 0.3-11.1 mm) at a mean follow-up of 14.1 months. Only two patients without evidence of endoleak exhibited growth of more than 5 mm at maximum follow-up (7.6 mm at 12 months and 11.1 mm at 36 months). Additional analysis of sealed endoleaks and late endoleaks failed to demonstrate any group with expansion in the absence of detectable endoleak.

CONCLUSIONS

Endotension appears to be rare in this large series of prospectively evaluated endografts. From this review, endotension seems more likely to represent missed endoleak than true aneurysm expansion in the absence of perigraft flow.

Serial CT volume measurements after endovascular aortic aneurysm repair

PURPOSE

To evaluate the efficacy of transluminal stent-graft placement in aortic aneurysms using postoperative enhanced spiral computed tomographic (CT) volumetric measurements of the aneurysm sac, the intra-aneurysmal vascular channel (IAVC), the thrombus, and the stent-graft.

METHODS

Among 53 patients (45 men; mean age 74 years, range 59-85) who underwent elective endovascular aortic aneurysm repair, 37 patients with 27 abdominal and 10 thoracic aortic aneurysms completed at least a 6-month follow-up that included computerized CT volumetric analysis prior to discharge and at 3, 6, 12, 24, and 36 months. A variety of bifurcated (n = 23) and tube (n = 14) stent-grafts were observed for signs of endoleak and aneurysm enlargement.

RESULTS

Mean follow-up was 16 months (range 6-48). Total aneurysm volumes and thrombus volumes decreased, whereas IAVC and stent-graft volumes increased over time. Between the postoperative and 12-month imaging studies, reductions in total aneurysm (p 0.011) and thrombus (p < 0.001) volumes were significant. No statistically significant difference in volume changes for the aneurysm sac (p = 0.555) or the thrombus (p = 0.920) was found when comparing the 24 patients without primary leak to the 12 with primary type-II leak. In all 5 cases with secondary leak, the volume of the aneurysm sac increased after initial shrinkage.

CONCLUSIONS

Postoperative CT volumetric analysis is an effective tool for evaluating the outcome of endovascular aortic aneurysm repair. Thrombus volume measurements are more accurate than total aneurysm volumes. In patients in whom contrast agents are contraindicated, volume measurements can also be obtained without the use of contrast.

Prospective evaluation of magnetic resonance imaging after endovascular treatment of infrarenal aortic aneurysms

OBJECTIVES

to evaluate the sensitivity and specificity of magnetic resonance imaging (MRI) in the detection of type II endoleaks during follow-up after endovascular treatment of intra-renal aortic aneurysms.

DESIGN

prospective study.

MATERIAL AND METHODS

between March 1996 and November 1999, 31 patients with infra-renal aortic aneurysms who underwent stentgraft implantation were followed with helical CT and MRI, including magnetic resonance angiography (MRA), at 1 and 6 months after the procedure. Arteriography was performed between 6 and 12 months after intervention. The parameters studied included the change in the maximum anteroposterior and transverse diameters, the nature of the signal on T1 and T2 weighted sequences (homogeneous vs heterogeneous), the presence or absence of Gadolinium uptake on MRI or of contrast uptake on helical CT (early and late phases) in the sac of the aneurysm. On MRA, stentgraft patency and endoleak detection were studied.

RESULTS

arteriography demonstrated an endoleak in 19 patients (18 type II, and 1 type I endoleak). MRI at 6 months detected 18/19 endoleaks on T1 weighted sequences after injection of Gadoliniumj; there were 2 false positives. MRA sequences confirmed stentgraft patency in all patients, but did not diagnose type II endoleaks. Helical CT (late phase) at 6 months detected 10/19 endoleaks; there was 1 false positive. The sensitivity of MRI after injection of Gadolinium and of helical CT for the detection of type II endoleaks were 94% and 50% (p=0.003) respectively. The mean maximal anteroposterior and transverse diameters were similar on MRI and on helical CT at 1 month and at 6 months.

CONCLUSION

MRI after injection of Gadolinium is more sensitive than helical CT in the detection of type II endoleaks after stentgraft implantation. Its more widespread use may permit earlier intervention in such patients.

Endoleak after endovascular repair of abdominal aortic aneurysm

PURPOSE

We sought to assess the role of endovascular techniques in the management of perigraft flow (endoleak) after endovascular repair of an abdominal aortic aneurysm.

METHOD

We performed endovascular repair of abdominal aortic aneurysm in 114 patients, using a variety of Gianturco Z-stent-based prostheses. Results were evaluated with contrast-enhanced computed tomography (CT) at 3 days, 3 months, 6 months, 12 months, and every year after the operation. An endoleak that occurred 3 days after operation led to repeat CT scanning at 2 weeks, followed by angiography and attempted endovascular treatment.

RESULTS

Endoleak was seen on the first postoperative CT scan in 21 (18%) patients and was still present at 2 weeks in 14 (12%). On the basis of angiographic localization of the inflow, the endoleak was pure type I in 3 cases, pure type II in 9, and mixed-pattern in 2. Of the 5 type I endoleaks, 3 were proximal and 2 were distal. All five resolved after endovascular implantation of additional stent-grafts, stents, and embolization coils. Although inferior mesenteric artery embolization was successful in 6 of 7 cases and lumbar embolization was successful in 4 of 7, only 1 of 11 primary type II endoleaks was shown to be resolved on CT scanning. There were no type III or type IV endoleaks (through the stent-graft). Endoleak was associated with aneurysm dilation two cases. In both cases, the aneurysm diameter stabilized after coil embolization of the inferior mesenteric artery. There were two secondary (delayed) endoleaks; one type I and one type II. The secondary type I endoleak and the associated aneurysm rupture were treated by use of an additional stent-graft. The secondary type II endoleak was not treated.

CONCLUSIONS

Type I endoleaks represent a persistent risk of aneurysm rupture and should be treated promptly by endovascular means. Type II leaks are less dangerous and more difficult to treat, but coil embolization of feeding arteries may be warranted when leakage is associated with aneurysm enlargement.

Hypogastric artery aneurysm rupture after endovascular graft exclusion with shrinkage of the aneurysm: significance of endotension from a "virtual," or thrombosed type II endoleak

Type II endoleaks, resulting from retrograde branch flow, after endovascular graft aneurysm exclusion are considered benign because they usually thrombose and are commonly associated with stable or shrinking aneurysm sacs. We report a hypogastric artery aneurysm rupture from endotension from an undetected, thrombosed Type II endoleak, associated with sac shrinkage. The patient had undergone an endovascular graft repair of a 4-cm right common iliac artery and 9-cm hypogastric artery aneurysm with distal hypogastric artery coil embolization. Serial computed tomography scans revealed no endoleak and a hypogastric aneurysm thrombosis with shrinkage. Eighteen months later, the aneurysm ruptured as a result of pressurization from backbleeding, patent branches.

All sealed endoleaks are not the same: a treatment strategy based on an ex-vivo analysis

PURPOSE

factors contributing to pressure transmission through thrombosed or sealed endoleaks have not been elucidated. The purpose of this investigation was to create an ex-vivo model that mimics patent and sealed endoleaks and that can quantitatively analyse the effects of length, diameter and thrombus on pressure transmission to the interior of the aneurysm sac.

METHODS

In the ex-vivo model, endoleak channels (ELCs) of various lengths (2 cm, 6 cm, 10 cm) and diameters (0.6 cm, 1.0 cm, 1.4 cm) were constructed using polytetrafluoroethylene (PTFE) grafts and attached to an artificial aneurysm sac. These ELCs were incorporated within a mock circulation made of rubber tubing connected to a pulsatile pump. Peak systolic pressure (PSP) was recorded in the aneurysm sac, distal to each ELC. Subsequently the ELCs were filled with human thrombus, and the pressure measurements repeated (n =5). Data was evaluated by regression analysis.

RESULTS

Peak systolic pressure in the artificial circulation was maintained at 150 mmHg. In the absence of thrombus pressure did not change across the ELC, regardless of its length or diameter. In the presence of organised thrombus, the pressure curves distal to the ELC were dampened, and the pressure reduction was directly proportional to the length and inversely proportional to the diameter of the ELC. Regression analysis indicated statistical significance.

CONCLUSION

In the absence of thrombosis, pressure transmitted via an ELC to the aneurysm sac is unchanged regardless of its length or diameter. All sealed endoleaks also transmit pressure. However, when an endoleak has thrombosed, pressure reduction is directly proportional to the length and inversely proportional to the diameter of its channel. This ex-vivo model suggests that Type 2 endoleaks with longer channels and smaller diameters would derive a greater benefit from adjunctive manoeuvres (coil embolisation) that hasten thrombosis. On the other hand, thrombosis of endoleaks with short and wide channels (e.g. Type 1) may not result in substantial pressure reduction within the aneurysm sac and a successful outcome.