Imaging modalities for the detection and management of endoleaks

EVAR and OPEN treatment of abdominal aortic aneurysm: What is the role of MMP-9 in the follow-up?

INTRODUCTION

The aim of our study is to verify the role of metalloproteinases in endovascular repair (EVAR) and OPEN surgery treatment for abdominal aortic aneurysm (AAA). Postoperatively, these enzymes could represent an important biomarker to adapt diagnostic tests and further investigations during follow-up.

MATERIAL AND METHOD

From 2004 to 2008, 55 patients were considered with AAA. Of these, 33 patients (mean age: 70.1 years), (mean AAA diameter: 5.4cm) were treated with OPEN surgery (group A) and 22 (mean age: 74.1 years) (mean AAA diameter: 5.1cm) were treated with EVAR. In 17 of them, there were no signs of endoleak (group B1), while in 5 patients, a presence of endoleak (group B2) was detected. Plasma samples were collected in order to determine MMP-9 activity. Enzyme immunoassay was performed preoperatively at 1, 3, 6 and 12 months. Patients treated conventionally were clinically examined after 1 and 12 months by ultrasound. Patients undergoing EVAR treatment were clinically examined by CT scan after 1, 3, 6 and 12 months. The analysis was done by assessing the interaction over time of the MMP-9 value in B1 and B2 groups.

RESULTS

The average values observed for MMP-9 were preoperatively and at 1, 3, 6 and 12 months, respectively: in group A 150.8ng/mL (SD=30.5), 252.5ng/mL (SD=25.2), 315.4ng/mL (SD=22.7), 295.3ng/mL (SD=26.8), 210.7ng/mL (SD=30.2); in group B1 105ng/mL (SD=10.8), 125.6ng/mL (SD=18), 85.8ng/mL (SD=19.9), 95ng/mL (SD=20.2), 80.4ng/mL (SD=15.6); in group B2 149ng/mL (29.2), 375.4ng/mL (SD=40.2), 215ng/mL (SD=35.9), 180ng/mL (SD=20.2), 175ng/mL (SD=33.4). The MMP-9 level was higher in group B2 compared to group B1 (P=0.01), suggesting a correlation with the presence of the endoleak.

CONCLUSIONS

This preliminary study shows that MMP-9 may be a biomarker of the presence of endoleak. Other further investigations and larger series are needed to show that metalloproteases could play a role in the follow-up of EVAR treated patients.

Prospective Comparison of Reduced-Iodine-Dose Virtual Monochromatic Imaging Dataset From Dual-Energy CT Angiography With Standard-Iodine-Dose Single-Energy CT Angiography for Abdominal Aortic Aneurysm

OBJECTIVE

The purpose of this study was to compare the image quality of reduced-iodine-dose single-source dual-energy CT angiography (CTA) with that of standard-iodine-dose single-energy CTA in examinations of patients with abdominal aortic aneurysm and to assess the effect of the concentration of iodinated contrast medium on intravascular enhancement and image quality of reduced-iodine-dose CTA.

SUBJECTS AND METHODS

In a prospective randomized clinical trial, 66 consecutively registered patients with abdominal aortic aneurysm who had previously undergone single-energy CTA (30-37 g I) underwent follow-up CTA at a reduced dose (21-27 g I) of iodinated contrast medium of either 270 mg I/mL (n = 33) or 320 mg I/mL (n = 33). Two readers independently evaluated virtual monochromatic imaging datasets (40-140 keV) and single-energy CTA images for image quality and noise and their preference for optimal energy virtual monochromatic imaging dataset. A value of p < 0.05 was considered statistically significant.

RESULTS

All 66 dual-energy CTA examinations were rated diagnostic with mean image quality and image noise scores of 4.8 and 4.5 for reader 1 and 3.8 and 3.4 for reader 2 compared with single-energy CTA results of 4.5 and 4.2 for reader 1 and 4.5 and 4.1 for reader 2. Low-energy virtual monochromatic images (40-60 keV) from reduced-iodine-dose (28%) dual-energy CTA had significantly higher intravascular aortic attenuation (26-185%) and contrast-to-noise ratio (CNR) (20-25%) than standard-iodine-dose single-energy CTA images (p < 0.0001). No significant difference was found between patients who received 270 and those who received 320 mg I/mL with respect to intravascular aortic attenuation (p = 0.6331) or CNR (p = 0.9775).

CONCLUSION

Low-energy virtual monochromatic imaging datasets from reduced-iodine (24 g I) single-source dual-energy CTA of the abdomen provide up to 185% higher attenuation and 25% higher CNR than standard-iodine-dose (33.3 g I) single-energy CTA while offering a wide range of energy settings irrespective of the concentration of IV contrast medium used.

Surveillance Imaging Following Endovascular Aneurysm Repair

There is a significant risk of complication following endovascular abdominal repair (EVAR), including endoleak, graft translocation, thrombosis, and infection. Surveillance imaging is important for detecting EVAR complication. Surveillance modalities include conventional X-ray, computed tomography, magnetic resonance imaging, ultrasound, and conventional angiography, with inherent advantages and drawbacks to each modality. The authors present common complications following EVAR, and recent advances in the key modalities for surveillance.

Surveillance of Endovascular Aneurysm Repair: An Audit of Sonographer-Led Ultrasound and Radiologist-Led Computed Tomography Services

Objectives

Postoperative complications associated with endovascular aneurysm repair (EVAR) mandate the need for lifelong surveillance. The aim of this audit was to compare the detection rates of endoleaks during the first 10 months of a combined sonographer-led colour Doppler ultrasound (CDUS) and radiologist-led contrast-enhanced computed tomography (CECT), postoperative EVAR surveillance programme, within a single National Health Service Hospital.

Methods

A prospective audit was carried out of all patients with EVAR, who had same-day CECT and CDUS surveillance examinations between March 2010 and January 2011. CECT examinations were reported by three consultant vascular radiologists. Of 66 CDUS examinations, 64 (97%) were performed and reported by four certified vascular sonographers. The reports of dual-modality, same-day scans were compared, to establish agreement on the presence and classification of the type, or absence of endoleaks. CECT was used as the gold standard, against which the sensitivity and specificity of CDUS in endoleak detection was determined.

Results

Sixty-six paired same-day CECT and CDUS reports were compared. Ten endoleaks were identified by CECT (15% incidence) and eight (80%) of 10 were type II. The number of observed agreements was 58 (88%) of 66; CDUS missed six endoleaks (five type II) and suggested two false-positives. CDUS had a sensitivity of 40% and a specificity of 96%. Conclusions: In our study, CDUS demonstrated an excellent specificity but had a low sensitivity for endoleak detection. We agree CDUS cannot effectively replace CECT as the sole imaging modality. Research to determine an international consensus for an effective and efficient postoperative EVAR surveillance patient pathway is required.

Treatment of complications following endovascular repair of abdominal aortic aneurysms

Endovascular aneurysm repair (EVAR) is an important treatment option for abdominal aortic aneurysms, with lower perioperative morbidity and mortality rates than open surgical aneurysm repair. However, EVAR is associated with several unique complications that are not encountered with surgical repair such as endoleaks, graft migration, and renal artery occlusion. Preservation of the morbidity and mortality advantages of EVAR relies on the successful treatment of these complications by minimally invasive, endovascular approaches. Some of the techniques used to treat EVAR complications include balloon dilation and stenting, deployment of additional stent-graft pieces, coil embolization, and thrombolysis. Although the employment of these endovascular salvage techniques is common, data regarding their intermediate- to long-term efficacy is sparse, and further studies are needed to determine their efficacy in preventing conversion to open aneurysm repair and aneurysm rupture.

Imaging Surveillance following Endovascular Aneurysm Repair

Endoleaks are unique complications of endovascular aneurysm repair (EVAR) that necessitate lifelong imaging surveillance for the patient. Several imaging modalities may be used to monitor the patient for endoleaks and other complications related to the stent graft. At present, computed tomographic angiography remains the gold standard for the detection of endoleaks. Other modalities that can be used to detect endoleaks include magnetic resonance, ultrasonography, nuclear medicine techniques, and pressure monitoring. In addition, follow-up imaging with digital subtraction angiography is important for endoleak classification and to guide decisions regarding therapy. In this article, we review the classification of endoleaks and discuss the different imaging strategies available for post-EVAR surveillance.

Predictive factors for endoleaks after thoracic aortic aneurysm endograft repair

BACKGROUND

Our prospective investigation aimed to determine and analyze the incidence and the determinants of endoleaks after thoracic stent graft.

METHODS

Sixty-one patients affected by thoracic aortic aneurysms were treated between January 2000 and March 2008. The study cohort contained 54 men, with a mean age of 63.6 +/- 17.9 years. The follow-up imaging protocol included chest radiographs and triple-phase computed tomographic angiography performed at 1, 4, and 12 postoperative months and annually thereafter.

RESULTS

Median follow-up was 32.4 months (range: 1-96 months). Endoleaks were detected in 9 (14.7%) patients, of which 7 were type 1. Five endoleaks were detected at 30 postoperative days, and the other 4 developed with a mean delay of 12 months. Endovascular or hybrid interventions were used to treat the endoleaks. Secondary technical success rate was 100%. Multivariate analysis demonstrated that the diameter of the aneurysmal aorta (odds ratio 1.75, 95% confidence interval 1.07-2.86) and the coverage of the left subclavian artery (odds ratio 12.05, 95% confidence interval 1.28-113.30) were independently associated with endoleak development. The percentages of patients in whom reinterventions were unnecessary were 94.6% +/- 3.0%, 88.3% +/- 4.5%, and 85.4% +/- 5.2%, at 1, 2, and 5 years, respectively. The actuarial survival estimates at 1, 2, and 5 years were 85.2% +/- 4.6%, 78.1% +/- 5.4%, and 70.6% +/- 6.4%, respectively.

CONCLUSIONS

The diameter of the aneurysmal aorta and the position of the landing zone are independent predictors of endoleak occurrence after thoracic stent-graft procedures. A careful follow-up program should be considered in patients in whom these indices are unfavorable, because most of the endoleaks may be successfully and promptly treated by additional endovascular procedures.

Endoleaks after endovascular repair of thoracic aortic aneurysms

OBJECTIVE

Endoleaks are one of the unique complications seen after endovascular repair of thoracic aortic aneurysms (TEVAR). This investigation was performed to evaluate the incidence and determinants of endoleaks, as well as the outcomes of secondary interventions in patients with endoleaks, after TEVAR.

METHODS

Over a 6-year period, 105 patients underwent TEVAR in the context of pivotal Food and Drug Administration trials with the Medtronic Talent (n = 64) and Gore TAG (n = 41) devices. The medical and radiology records of these patients were reviewed for this retrospective study. Of these, 69 patients (30 women and 39 men) had follow-up longer than 1 month and were used for this analysis. The patients were evaluated for the presence of an endoleak, endoleak type, aneurysm expansion, and endoleak intervention.

RESULTS

The mean follow-up in this patient cohort was 17.3 +/- 14.7 months (range, 3-71 months). Endoleaks were detected in 29% (20/69) of patients, of which 40% (8/20) were type I, 35% (7/20) were type II, 20% (4/20) were type III, and 5% (1/20) had more than one type of endoleak. Patients without endoleaks experienced greater aneurysm sac regression than those with endoleaks (-2.89 +/- 9.1 mm vs -0.13 +/- 7.2 mm), although this difference was not statistically significant (P = .232). All but 2 endoleaks (90%; 18/20) were detected on the initial postoperative computed tomographic scan at 30 days. Two endoleaks (10%; 2/20) developed late. The endoleak group had more extensive aneurysms with significantly larger aneurysms at the time of intervention (69.4 +/- 10.5 mm vs 60.6 +/- 11.0 mm; P = .003). Factors predictive of endoleak included male sex (P = .016), larger aneurysm size (P = .003), the length of aorta treated by stent grafts (P = .0004), and an increasing number of stents used (P < .0001). No open conversions were performed for treatment of endoleaks. Four (50%) of the eight type I endoleaks were successfully repaired by using endovascular techniques. None of the type II endoleaks was treated by secondary intervention. During follow-up, the maximum aneurysm diameter in the type II endoleak patients increased a mean of 2.94 +/- 7.2 mm (range, -4.4 to 17 mm). Spontaneous thrombosis has occurred in 29% (2/7) of the type II endoleaks. Patients with type III endoleaks experienced a decrease in mean maximal aneurysm diameter of 0.78 +/- 3.1 mm during follow-up.

CONCLUSIONS

Endoleaks are not uncommon after TEVAR. Many type I endoleaks may be treated successfully by endovascular means. Short-term follow-up suggests that observational management of type II endoleaks is associated with continued sac expansion, and these patients should be monitored closely.

Recurrent endoleak detection and measurement of aneurysm size with CTA after coil embolization of endoleaks

PURPOSE

The optimal modality for following aneurysm size and detecting endoleaks after endovascular aneurysm repair (EVAR) remains controversial. Computed tomographic angiography (CTA) has been widely employed but can be limited by metal artifact from stents, which is exacerbated by embolization coils placed during the treatment of type 2 endoleaks. The authors assessed interobserver agreement of CTA for measuring aneurysm size and presence of recurrent endoleak in patients with prior coil embolization of type 2 endoleaks.

MATERIALS AND METHODS

A total of 65 CTAs were retrospectively reviewed in a cohort of 27 patients (25 men; two women; mean age, 77.4 years) who had prior endoleak embolization after EVAR. Endoleak embolizations included transarterial (n=8) and translumbar (n=19) approaches. In each patient, maximal aneurysm diameter and presence/absence of recurrent endoleak was measured independently by two observers. Cohen's Kappa statistic was used to assess interobserver agreement, as well as paired two-tailed Student t tests for aneurysm diameter.

RESULTS

Recurrent type 2 endoleaks were detected with CTA in eight of 27 patients (30%) and on 13 of 65 CTAs (20%). A high degree of correlation (98.5%) was also seen between the two observers for presence of endoleak (Kappa=0.95). Mean aneurysm diameter for the entire cohort correlated closely between both observers: 54.8 mm+/-1.1 for observer A and 54.9 mm+/-1.1 for observer B (P=.66). There was a disagreement between the readers of greater than 2 mm regarding aneurysm size in 13.8% of the CTAs (nine of 65 CTAs).

CONCLUSION

Despite the presence of streak artifact on CTA following coil embolization of type 2 endoleaks, CTA remains a useful study for following patients. The presence of embolization coils does not prevent CTA measurement of aneurysm diameter and detection of recurrent endoleak with a high degree of interobserver agreement.

Use of CT Angiography to Classify Endoleaks after Endovascular Repair of Abdominal Aortic Aneurysms

PURPOSE

Accurate endoleak detection and classification is critical for the follow-up of patients who have undergone endovascular aneurysm repair (EVAR). This determination is often made with computed tomography angiography (CTA). This investigation was performed to determine the accuracy of CTA in the classification of endoleaks in patients who have undergone EVAR.

MATERIALS AND METHODS

Thirty-six patients with endoleaks underwent both CTA and conventional contrast digital subtraction angiography (DSA) to determine endoleak etiology. Two independent radiologists determined the source of the endoleak based on a retrospective review of the CTA. The results of the CTA-based endoleak classification were compared to the reference standard, contrast DSA.

RESULTS

There was agreement regarding endoleak classification between CTA and DSA on 86% of the patients (31 of 36 patients). Correlation between the CTA reading of the two readers was 94% (34 of 36 patients), yielding a kappa statistic of 0.8. In three patients, the CTA reading incorrectly classified endoleaks as type 2 when the endoleaks were actually type 1 endoleaks on DSA. One patient was incorrectly classified as having a type 1 endoleak on CTA when it was a type 2 endoleak on DSA. Finally, one patient had a type 1 endoleak on DSA that was incorrectly classified as a type 3 endoleak on CTA. The change in CTA endoleak classification based on the DSA resulted in a significant change in patient management in four of the 36 patients (11%).

CONCLUSIONS

Endoleak classification based on CTA correlates fairly well with DSA findings. However, optimal endoleak management requires performance of selective angiograms with DSA to classify endoleaks that are detected on CTA.

Catheter-based treatments of endoleaks

At the present time, patients who have undergone endovascular aneurysm repair require lifelong surveillance. The purpose of this surveillance is threefold. First, has there been any change in the position of the endograft? Secondly, what is the status of the aneurysm sac? Thirdly, is there an endoleak? How the patient is managed depends on the answers to these three questions. Managing patients with endoleaks remains a challenging clinical problem. Decisions on these patients depend on the type of leak and the status of the aneurysm sac. This manuscript will review what is currently known about endoleaks and use this information to develop algorithms of how patients should be treated.