Flow dynamics of type II endoleaks can determine sac expansion after endovascular aneurysm repair using four-dimensional flow-sensitive magnetic resonance imaging analysis

An Expert-Based Review on the Relevance and Management of Type 2 Endoleaks Following Endovascular Repair of Ruptured Abdominal Aortic Aneurysms

Ruptured abdominal aortic aneurysms (rAAAs) are life-threatening and require emergent surgical therapy. Endovascular aortic repair for rupture (rEVAR) has become the leading strategy due to its minimal invasive approach with expected lower morbidity and mortality, especially in patients presenting with hemodynamic instability and relevant comorbidities. Following rEVAR, intraoperative angiography or early postinterventional computed tomography angiography have to exclude early type 1 or 3 endoleaks requiring immediate reintervention. Persistent type 2 endoleaks (T2ELs) after rEVAR, in contrast to elective cases, can cause possibly lethal situations due to continuing extravascular blood loss through the remaining aortic aneurysm rupture site. Therefore, early identification of relevant persistent T2ELs associated with continuous bleeding and hemodynamic instability and immediate management is mandatory in the acute postoperative setting following rEVAR. Different techniques and concepts for the occlusion of T2ELs after rEVAR are available, and most of them are also used for relevant T2ELs after elective EVAR. In addition to various interventional embolization procedures for persistent T2ELs, some patients require open surgical occlusion of T2EL-feeding arteries, abdominal compartment decompression or direct surgical patch occlusion of the aneurysm rupture site after rEVAR. So far, in the acute situation of rAAAs, indications for preemptive or intraoperative T2EL embolization during rEVAR have not been established. In the long term, persistent T2ELs after rEVAR can lead to continuous aneurysm expansion with the possible development of secondary proximal type I endoleaks and an increased risk of re-rupture requiring regular follow-up and early consideration for reintervention. To date, only very few studies have investigated T2ELs after rEVAR or compared outcomes with those from elective EVAR regarding the special aspects of persisting T2ELs. This narrative review is intended to present the current knowledge on the incidence, natural history, relevance and strategies for T2EL management after rEVAR.

Early and Mid-Term Outcomes of Transcaval Embolization for Type 2 Endoleak after Endovascular Aortic Repair

Background: Among the endovascular approaches for the management of endoleak type 2 (EL 2), transcaval embolization (TCE) has shown encouraging outcomes. However, the literature is still limited. This study aimed to present the early and mid-term outcomes of TCE for EL 2 after endovascular aortic repair. Methods: A retrospective, single-center analysis of consecutive patients managed with TCE for EL 2 after standard or complex endovascular aortic repair, from August 2015 to March 2024, was conducted. The indication for TCE was the presence of an EL 2 related to ≥5 mm sac increase, compared to the first imaging after aneurysm exclusion or the smallest diameter during follow-up. Patients managed with TCE for other types of endoleaks were excluded. The primary outcomes were technical and clinical successes during follow-up. Results: Forty-three patients were included (mean age: 75.1 ± 6.0 years, 90.7% males). Technical success was 97.7%. Selective embolization was performed in 48.8% and non-selective in 51.2%. No death was recorded at 30 days. The estimated clinical success was 90.0% (standard error; SE: 6.7%) and the freedom from EL 2 was 89.0% (SE 6.4%) at 36 months. Cox regression analysis showed that the type of embolization (selective vs. non-selective), type of previous repair (f/bEVAR vs. EVAR), and use of anticoagulants did not affect follow-up outcomes. Reinterventions related to EL 2 were performed in 12.5%; three underwent an open conversion. Conclusions: TCE was related to high technical success and limited peri-operative morbidity, regardless of the type of initial endovascular aortic repair. Clinical success was encouraging with reinterventions for EL 2 affecting 12.5% of patients.

Image Guidance Techniques and Treatment Approach Optimization in the Management of Type-II Endoleak After Endovascular Aortic Aneurysm Repair

BACKGROUND

Over the past 3 decades endovascular aortic aneurysm repair emerged as the primary approach for abdominal aortic aneurysm management, however the occurrence of endoleak following endograft implantation imposes a high toll on patients and hospitals alike. The early diagnosis and appropriate treatment of endoleaks is associated with better outcomes, which calls for more advanced imaging and a standardized approach for endoleak diagnosis and management following endovascular aortic aneurysm repair. Although conventional strategy with non-targeted deployment of coils and embolic material in the aneurysm sac is considered to be the standard approach in many hospitals, it may not prove to be a viable option, given that it affects any further follow-up imaging in the event of sub-optimal therapy and consequent recurrence.

METHODS

Based on our tertiary aortic referral center experience we summarize and describe strategies for optimal selection of various treatment approaches for Type-II Endoleak management including endovascular, percutaneous and laparoscopic approaches with particular focus on intraoperative image guidance techniques.

RESULTS

After failed conventional endovascular embolization attempt we recommend specific complex type II endoleak management approaches based on the location of the endoleak within the aneurysm sac along the x, y and z axis. A transabdominal or laparoscopic approach enable treatment in endoleaks located in the anterior portion of the sac. Endoleaks in the posterior portion of the sac could be treated using the transcaval or the translumbar approach, depending on whether the endoleak is situated on the left or the right side. Alternative strategies should be considered if patient anatomy does not allow for either transcaval or translumbar approach. The transgraft technique is reserved for endoleaks located in the cranial portion of the sac, while the perigraft approach could present a means of treatment for endoleaks situated in the caudal portion of the aneurysm sac.

CONCLUSION

We encourage establishing a patient specific treatment plan in accordance with individual anatomy based on cross sectional imaging modality (time resolved dynamic imaging in selected cases) and intraoperative image guidance to provide a safe and accurate endoleak localization and embolization for patients undergoing type II endoleak treatment.

Endograft position and endoleak detection after endovascular abdominal aortic repair with low-field tiltable MRI: a feasibility study

BACKGROUND

Abdominal aortic endoleaks after endovascular aneurysm repair might be position-dependent, therefore undetectable using supine imaging. We aimed to determine the feasibility and benefit of using a low-field tiltable magnetic resonance imaging (MRI) scanner allowing to study patients who can be imaged in both supine and upright positions of endoleaks.

METHODS

Ten EVAR patients suspected of endoleak based on ultrasound examination were prospectively included. MRI in upright and supine positions was compared with routine supine computed tomography angiography (CTA). Analysis was performed through (1) subjective image quality assessment by three observers, (2) landmark registration between MRI and CTA scans, (3) Euclidean distances between renal and endograft landmarks, and (4) evaluation of endoleak detection on MRI by a consensus panel. Statistical analysis was performed by one-way repeated measures analysis of variance.

RESULTS

The image quality of upright/supine MRI was inferior compared to CTA. Median differences in both renal and endograft landmarks were approximately 6-7 mm between upright and supine MRI and 5-6 mm between supine MRI and CTA. In the proximal sealing zone of the endograft, no differences were found among all three scan types (p = 0.264). Endoleak detection showed agreement between MRI and CTA in 50% of the cases, with potential added value in only one patient.

CONCLUSIONS

The benefit of low-field upright MRI for endoleak detection was limited. While MRI assessment was non-inferior to standard CTA in detecting endoleaks in selected cases, improved hardware and sequences are needed to explore the potential of upright MRI in patients with endoleaks.

RELEVANCE STATEMENT

Upright low-field MRI has limited clinical value in detecting position-dependent endoleaks; improvements are required to fulfil its potential as a complementary modality in this clinical setting.

KEY POINTS

• Upright MRI shows potential for imaging endoleaks in aortic aneurysm patients in different positions. • The image quality of upright MRI is inferior to current techniques. • Upright MRI complements CTA, but lacks accurate deformation measurements for clinical use. • Advancements in hardware and imaging sequences are needed to fully utilise upright MRI capabilities.

Pre-Operative Four Dimensional Flow Sensitive Magnetic Resonance Imaging Assessment of Aortic Side Branches as a Method to Predict Risk of Type II Endoleak Resulting in Sac Enlargement After EVAR

OBJECTIVE

To predict sac enlargement with type II endoleak (ELII) before endovascular aneurysm repair (EVAR) using four dimensional flow sensitive magnetic resonance imaging (4D flow MRI).

METHODS

A single centre retrospective analysis of prospectively collected data was conducted. Patients with an abdominal aortic aneurysm (AAA) who underwent EVAR between 2013 and 2019 were included. Aortic branches occluded pre-EVAR, and patients with endoleaks other than ELII were excluded. The aortic branch diameter, peak flow velocity (PFVe), and amplitude of the dynamics of flow volume (AFV) were measured in each aortic branch pre-EVAR. Total flow volume per minute (TFV/min), defined as the sum of AFV/min, was calculated in each case. According to computed tomography findings one year post-EVAR, the aortic branches and patients were divided into patent vessel and occluded vessel groups and sac expanding and non-expanding groups. PFVe, AFV/min, and TFV/min were analysed via receiver operating characteristic curve analysis.

RESULTS

The patent aortic branches pre-EVAR (69 inferior mesenteric arteries [IMAs]; 249 lumbar arteries [LAs]) of 100 patients were included. Patent IMAs (n = 14) and occluded IMAs (n = 55), patent LAs (n = 23) and occluded LAs (n = 226), and expanding (n = 9) and non-expanding (n = 91) groups were compared, respectively. No statistically significant difference was observed in branch diameters (IMA; patent, 2.5 ± 0.8 mm, occluded, 2.5 ± 0.8 mm, p < .78 and LA; patent, 1.5 ± 0.3 mm, occluded, 1.5 ± 0.4 mm, p < .35). PFVe (IMA; patent, 262.6 mm2/sec, occluded, 183.4 mm2/sec and LA; patent, 142.6 mm2/sec, occluded, 47.7 mm2/sec) and AFV/min (IMA; patent, 8.4 mL, occluded, 5.2 mL and LA; patent, 4.2 mL, occluded, 1.4 mL) were higher in the patent vessel group (p < .050). TFV/min was statistically significantly higher in the expanding group (24.1 mL/min) than in the non-expanding group (7.0 mL/min) (p < .010).

CONCLUSION

Pre-EVAR haemodynamic analyses using 4D flow MRI were useful to detect aortic branches responsible for ELII and to predict AAA cases with sac enlargement. This analysis suggests a new strategy for pre-EVAR aortic branch embolisation.

Four-Dimensional Flow MRI for the Evaluation of Aortic Endovascular Graft: A Pilot Study

We aimed to explore the feasibility of 4D flow magnetic resonance imaging (MRI) for patients undergoing thoracic aorta endovascular repair (TEVAR). We retrospectively evaluated ten patients (two female), with a mean (±standard deviation) age of 61 ± 20 years, undergoing MRI for a follow-up after TEVAR. All 4D flow examinations were performed using a 1.5-T system (MAGNETOM Aera, Siemens Healthcare, Erlangen, Germany). In addition to the standard examination protocol, a 4D flow-sensitive 3D spatial-encoding, time-resolved, phase-contrast prototype sequence was acquired. Among our cases, flow evaluation was feasible in all patients, although we observed some artifacts in 3 out of 10 patients. Three individuals displayed a reduced signal within the vessel lumen where the endograft was placed, while others presented with turbulent or increased flow. An aortic endograft did not necessarily hinder the visualization of blood flow through 4D flow sequences, although the graft could generate flow artifacts in some cases. A 4D Flow MRI may represent the ideal tool to follow up on both healthy subjects deemed to be at an increased risk based on their anatomical characteristics or patients submitted to TEVAR for whom a surveillance protocol with computed tomography angiography would be cumbersome and unjustified.

ACR Appropriateness Criteria® Thoracoabdominal Aortic Aneurysm or Dissection: Treatment Planning and Follow-Up

As the incidence of thoracoabdominal aortic pathology (aneurysm and dissection) rises and the complexity of endovascular and surgical treatment options increases, imaging follow-up of patients remains crucial. Patients with thoracoabdominal aortic pathology without intervention should be monitored carefully for changes in aortic size or morphology that could portend rupture or other complication. Patients who are post endovascular or open surgical aortic repair should undergo follow-up imaging to evaluate for complications, endoleak, or recurrent pathology. Considering the quality of diagnostic data, CT angiography and MR angiography are the preferred imaging modalities for follow-up of thoracoabdominal aortic pathology for most patients. The extent of thoracoabdominal aortic pathology and its potential complications involve multiple regions of the body requiring imaging of the chest, abdomen, and pelvis in most patients. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Postendovascular Aneurysmal Repair Increase in Local Energy Loss for Fusiform Abdominal Aortic Aneurysm: Assessments With 4D flow MRI

BACKGROUND

Although endovascular aneurysmal repair (EVAR) is a preferred treatment for abdominal aortic aneurysm (AAA) owing to its low invasiveness, its impact on the local hemodynamics has not been fully assessed.

PURPOSE

To elucidate how EVAR affects the local hemodynamics in terms of energy loss (EL).

STUDY TYPE

Prospective single-arm study.

FIELD STRENGTH/SEQUENCE

A 3.0 T/4D flow MRI using a phase-contrast three-dimensional cine-gradient-echo sequence.

POPULATION

A total of 13 consecutive patients (median [interquartile range] age: 77.0 [73.0, 78.8] years, 11 male) scheduled for EVAR as an initial treatment for fusiform AAA.

ASSESSMENT

4D flow MRI covering the abdominal aorta and bilateral common iliac arteries and the corresponding stent-graft (SG) lumen was performed before and after EVAR. Plasma brain natriuretic peptide (BNP) was measured within 1 week before and 1 month after EVAR. The hemodynamic data, including mean velocity and the local EL, were compared pre-/post-EVAR. EL was correlated with AAA neck angle and with BNP. Patients were subdivided into deformed (N = 5) and undeformed SG subgroups (N = 8) and pre-/post-EVAR BNP compared in each.

STATISTICS

Parametric or nonparametric methods. Spearman's rank correlation coefficients (r). The interobserver/intraobserver variabilities with Bland-Altman plots. A P value < 0.05 is considered significant.

RESULTS

The mean velocity (cm/sec) at the AAA was five times greater after EVAR: 4.79 ± 0.32 vs. 0.91 ± 0.02. The total EL (mW) increased by 1.7 times after EVAR: 0.487 (0.420, 0.706) vs. 0.292 (0.192, 0.420). The total EL was proportional to the AAA neck angle pre-EVAR (r = 0.691) and post-EVAR (r = 0.718). BNP (pg/mL) was proportional to the total EL post-EVAR (r = 0.773). In the deformed SG group, EL (0.349 [0.261, 0.416]) increased 2.4-fold to 0.848 (0.597, 1.13), and the BNP 90.3 (53.6, 105) to 100 (67.2, 123) post-EVAR.

CONCLUSION

The local EL showed a 1.7-fold increase after EVAR. The larger increase in the EL in the deformed SG group might be a potential concern for frail patients.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 2.

Dynamic Imaging of Aortic Pathologies: Review of Clinical Applications and Imaging Protocols

The past decade has seen significant advances in dynamic imaging of the aorta. Today's vascular surgeons have the opportunity to choose from a wide array of imaging modalities to evaluate different aortic pathologies. While vascular ultrasound and aortography are considered to be the bread and butter imaging modalities, newer dynamic imaging techniques provide time-resolved information in various aortic pathologies. However, despite growing evidence of their advantages in the literature, they have not been routinely adopted. In order to understand the role of these emerging modalities, one must understand their principles, advantages, and limitations in the context of various clinical scenarios. In this review, we provide an overview of dynamic imaging techniques for aortic pathologies and describe various dynamic computed tomography and magnetic resonance imaging protocols, clinical applications, and potential future directions.

Abdominal applications of quantitative 4D flow MRI

4D flow MRI is a quantitative MRI technique that allows the comprehensive assessment of time-resolved hemodynamics and vascular anatomy over a 3-dimensional imaging volume. It effectively combines several advantages of invasive and non-invasive imaging modalities like ultrasound, angiography, and computed tomography in a single MRI acquisition and provides an unprecedented characterization of velocity fields acquired non-invasively in vivo. Functional and morphological imaging of the abdominal vasculature is especially challenging due to its complex and variable anatomy with a wide range of vessel calibers and flow velocities and the need for large volumetric coverage. Despite these challenges, 4D flow MRI is a promising diagnostic and prognostic tool as many pathologies in the abdomen are associated with changes of either hemodynamics or morphology of arteries, veins, or the portal venous system. In this review article, we will discuss technical aspects of the implementation of abdominal 4D flow MRI ranging from patient preparation and acquisition protocol over post-processing and quality control to final data analysis. In recent years, the range of applications for 4D flow in the abdomen has increased profoundly. Therefore, we will review potential clinical applications and address their clinical importance, relevant quantitative and qualitative parameters, and unmet challenges.

Clinical Application of 4D Flow MR Imaging for the Abdominal Aorta

Blood vessels can be regarded as autonomous organs. The endothelial cells on the vessel surface serve as mechanosensors or mechanoreceptors for the flow velocity and turbulence of the blood flow in terms of wall shear stress (WSS), thereby monitoring changes in the flow velocity. Accordingly, the endothelial cells regulate the flow velocity by releasing numerous mediators. Such regulatory systems also trigger atherosclerosis, where the WSS decreases or fluctuates to maintain the flow velocity or local WSS. As occurrences of abdominal aortic aneurysms and aortic dissection are closely related to atherosclerosis, understanding the hemodynamics of the abdominal aorta is necessary to obtain useful information concerning the pathogenesis, diagnosis, and interventions. 4D flow MRI is beneficial for measuring the hemodynamics through comprehensive retrospective flowmetry of the entire spatio-temporal distributions of the flow vectors. This section focuses on abdominal aortic aneurysms and aortic dissection as representative examples of abdominal aortic diseases. Their hemodynamic characteristics and how hemodynamics is involved in their progression are described, and how 4D flow MRI can contribute to their assessment is also explained.

Endotension: twenty years of a controversial term

Use of the term endotension in the treatment of aortic aneurysm is currently controversial. Initially it was proposed to define the circumstance in which there is an enlargement of the aneurysm sac after endovascular repair without a demonstrable endoleak. The term was established with the aim of transmitting the possibility of causes other than pressure applying stress to the aneurysm wall. Twenty years have passed since the proposal of this terminology was published. The literature is reviewed with the purpose of providing an update on advances in the knowledge of the possible etiological mechanisms. The experimental studies call into question that causes other than pressure determine the increase of the aneurysm. On the basis of this review, the term `Sac Expansion Without Evident Leak´ (SEWEL) is proposed as a more accurate and precise denomination for what is aimed to be defined. Evidence suggests that the more likely mechanisms of persistent pressurization of the aneurysm sac are an unidentified endoleak (likely type I or low-flow Type II) or thrombus occluding wide and short channels that connects with the excluded aneurysm sac (at the attachment sites of the stent-graft or at the branch vessels orifices).

Editor's Choice - Mid Term Outcomes of Crossed Limb vs. Standard Limb Configuration in Endovascular Abdominal Aortic Aneurysm Repair: A Propensity Score Analysis

OBJECTIVE

The aim was to compare mid term outcomes between crossed limb (CL) and standard limb (SL) configuration in patients who underwent endovascular aortic aneurysm repair (EVAR).

METHODS

This was a comparative cohort study. Eligible patients who underwent EVAR between September 2011 and March 2019 in a tertiary academic centre were included. Inverse probability of treatment weighting (IPTW) was used to balance the demographic, anatomical and operative baseline characteristics between the two groups. The primary outcome was adverse limb events including type IB endoleak (T1BEL), type III endoleak, and limb occlusion. Cox proportional hazards regression and marginal structural model were performed to compare time to event outcomes.

RESULTS

The study included 729 patients (194 CL and 535 SL) with a median follow up of 34 months (interquartile range 16 - 62 months). The weighted analyses revealed no significant difference between CL and SL EVAR in terms of adverse limb events, type IA endoleak (T1AEL), type II endoleak (T2EL), re-intervention, and overall survival. In the subgroup analysis of large aneurysm sac, the CL configuration was associated with a significantly decreased risk of T1BEL (hazard ratio [HR] 0.31, 95% confidence interval [CI] 0.12 - 0.78, p = .014). Similar results were also observed in the subgroup of tortuous iliac arteries (HR 0.30, 95% CI 0.11 - 0.81, p = .017). After stratification by severe neck angulation, no significant difference was found between CL and SL EVAR for T1AEL, but the CL configuration was associated with a significantly increased risk of re-intervention (HR 2.69, 95% CI 1.31 - 5.51, p = .007). In addition, a trend towards a higher risk of adverse limb events in the CL group with severely angulated proximal neck was observed.

CONCLUSION

CL configuration in EVAR is safe and may be associated with a lower risk of T1BEL in patients with a large aneurysm sac or tortuous iliac arteries. However, it should be applied cautiously to aneurysms with a severely angulated neck due to the potentially higher risk of re-intervention.

Surveillance Imaging following Endovascular Aneurysm Repair: State of the Art

Endovascular aneurysmal repair (EVAR) has become a prominent modality for the treatment of abdominal aortic aneurysm. Surveillance imaging is important for the detection of device-related complications, which include endoleak, structural abnormalities, and infection. Currently used modalities include ultrasound, X-ray, computed tomography, magnetic resonance imaging, and angiography. Understanding the advantages and drawbacks of each modality, as well available guidelines, can guide selection of the appropriate technique for individual patients. We review complications following EVAR and advances in surveillance imaging modalities.

Four-dimensional flow magnetic resonance imaging study to explain high prevalence of pulmonary vein stump thrombus after left upper lobectomy

Background

Pulmonary vein (PV) stump thrombus, a known source of cerebral infarction, develops almost exclusively after left upper lobectomy; however, the mechanism remains unclear. We therefore evaluated the hemodynamics in the left atrium with four-dimensional flow magnetic resonance imaging (4D-flow MRI), which enables the simultaneous depiction of blood flow at three locations and the evaluation of hemodynamics.

Methods

4D-flow MRI was basically performed 7 days after lobectomy for cancer arising in the right upper lobe (n=11), right lower lobe (n=8), left upper lobe (n=13), or left lower lobe (n=8). We evaluated dynamic blood movement from the ipsilateral remaining PV, the resected PV stump, and the contralateral PVs into the left atrium using 4D-flow MRI.

Results

There were some characteristic blood flow patterns that seemed to either promote or prevent PV stump thrombus. Promotive flow patterns were significantly more frequent and preventive flow patterns were significantly less frequent in patients who had undergone left upper lobectomy than in those who had undergone other lobectomy. Accordingly, the degree of blood turbulence near the vein stump, as measured by the extent of change in the blood movement, was significantly higher in patients who had undergone left upper lobectomy than in patients who had undergone other lobectomy.

Conclusions

Our study revealed that left upper lobectomy likely causes blood turbulence near the vein stump through complicated blood streams in the left atrium, which can play a part in the development of vein stump thrombus. Further study to identify patients at high risk of vein stump thrombus is warranted.

Predictive Factor of the Possibility for Aortic Side Branches Coil Embolization during Endovascular Abdominal Aortic Aneurysm Repair

Objective: Coil embolization of aortic side branches has been additionally performed to prevent type II endoleak during EVAR in our institute. In this study, we evaluated the predictive factors of the possibility for coil embolization of the inferior mesenteric artery (IMA) and lumbar artery (LA) during EVAR.

Methods: Seventy-four EVAR patients during June 2015 and April 2019 were included in the study. The coil embolization procedural time for one vessel is limited to 10 min. Aortic side branches were selected with 4 Fr Shepherd hook type catheter (Medikit, Tokyo, Japan) and were embolized with Interlock (Boston Scientific, MA, USA) via microcatheter. As predictive factors, internal diameter of aortic side branches and the aortic diameter perpendicular to the origin of LA (aortic diameter) were evaluated.

Results: Coil embolization was tried for 52 patent IMAs and all IMAs except two IMAs with ostial stenosis were successfully coil embolized (96.2%). Totally 190 LAs were patent and coil embolization was tried for 144 LAs. Among 144 LAs, 106 LAs (73.6%) were successfully coil embolized and the diameter was significantly longer (2.30±0.51 mm vs. 2.04±0.41 mm, p=0.007) and aortic dimeter was significantly shorter (30.0±8.1 mm vs. 40.5±11.6 mm, p<0.001) in successfully embolized LAs. Cut off value of successful LA coil embolization was 2.06 mm for internal diameter and 36.1 mm for aortic diameter by receiver operating characteristic curve analysis. Successful coil embolization rate for LAs with internal diameter longer than 2.0 mm and aortic diameter less than 36.2 mm was 90% (72 among 80 LAs).

Conclusion: Coil embolization during EVAR for IMA was highly successful, if there was no calcified ostial stenosis. LA embolization was feasible especially for LAs with internal diameter ≥2.0 mm and aortic diameter ≤36.1 mm. This information would be useful to select the target vessel for aortic side branches coil embolization during EVAR. (This is a translation of Jpn J Vasc Surg 2019; 28: 389–396.)

4D Flow when and how?

4D Flow is an emerging MR technique enabling three-dimensional and cardiac phase-resolved flowmetry with ECG-gated phase-contrast MRI that increased the speed of data acquisitions, accuracy and robustness. The method is promoting researches in areas that have not been fully addressed before in the cardiovascular system, such as flowmetry of the bloodstream across the valves, within the heart chambers, complexed flow dynamics such as vortex, helical or retrograde. Wall shear stress and other potential biomarkers derived from 4D Flow are known to be related to vascular wall diseases such as atherosclerosis. In this review, fundamental concepts of 4D Flow technique and post-processing, benefits and limitations as well as its clinical applications are discussed, and the importance of quality control and validation of the method is emphasized. New ideas inspired by 4D Flow can help clinicians and MR scientists further understand the role of flow dynamics in health sciences, diseases and various aspects of cardiovascular physiology.

Direct percutaneous embolization of aneurysm sac: a safe and effective procedure to treat post-EVAR type II endoleaks

PURPOSE

To report safety and effectiveness of type II endoleak embolization, with percutaneous direct aneurysm sac puncture.

MATERIALS AND METHODS

Fifty patients, 31 male (mean age 55 ± 5), with post-EVAR type-II endoleak underwent direct percutaneous sac puncture for embolization. Procedures were performed, under local anesthesia. Sac puncture was done using a 20G needle under rotational angiography guidance. A coaxial system (4 Fr catheter + 2.7 microcatheter) was used to navigate the sac. During the follow-up period, all patients underwent contrast-enhanced ultrasound (CEUS) at 6 and 12 months.

RESULTS

Technical success, with complete exclusion of the aneurysm sac, was achieved in all cases. Time of procedure varied between 36 and 68 min (mean 51.36 min). Mean fluoroscopy time was 16.7 min. A posterior left access was used in 41 cases, posterior right access in 6 cases, and an anterior approach in 3. In 19 cases (38%), one or more feeding vessels were visualized and embolized. Sac embolization was done using Onyx plus micro-coils in 31 cases (62%) and Onyx alone in 19 cases (38%). Mean amount of Onyx was 6 ml. No complications, correlated with the direct percutaneous sac puncture, or to Onyx injection occurred. After 1-year follow-up, sac shrinkage occurred in 34 cases (68%), while in 16 patients (32%) sac size remained stable without evidence of sac perfusion.

CONCLUSION

Percutaneous direct sac embolization using Onyx in combination or not with microcoils represents a safe and valid technique to solve post-EVAR type II endoleaks.

Surgical treatment patterns and clinical outcomes of patients treated for expanding aneurysm sacs with type II endoleaks after endovascular aneurysm repair

OBJECTIVE

Persistent type II endoleaks (T2ELs) after endovascular aneurysm repair (EVAR) with sac growth have been associated with adverse events, including rupture. Whereas intervention in the presence of aneurysm growth has become an accepted treatment paradigm for T2ELs, the efficacy and clinical success of such interventions remain unclear. Therefore, we examined the treatment patterns and clinical outcomes of patients undergoing T2EL interventions after EVAR.

METHODS

We performed a retrospective review of all patients treated for expanding aneurysm sacs with T2ELs after EVAR at an academic medical center between 2006 and 2017. The primary outcomes assessed were need for repeated intervention; intervention types; and achievement of clinical success, defined as stable aneurysm sac size on computed tomography angiography after treatment.

RESULTS

Fifty-six patients underwent 119 interventions, of which 107 (90%) were technically successful. The median time from EVAR to index T2EL procedure was 37 months (interquartile range, 17-56 months), and the median follow-up time from first T2EL procedure was 27 months (interquartile range, 10-51 months). The most common index procedure was transarterial lumbar embolization (64%), followed by transarterial inferior mesenteric artery (20%), transcaval (14%), and translumbar embolization (1.8%). Thirty-three (59%) patients required further procedures for persistent aneurysm sac expansion. For subsequent T2EL interventions, the most common endovascular procedure was transarterial lumbar embolization (21%), followed by transcaval (21%), translumbar (11%), and transarterial inferior mesenteric artery embolization (8.6%). Twelve patients (21%) were found to have loss of proximal or distal seal on subsequent imaging and required graft extensions to stabilize aneurysm sac size. Ten patients (18%) ultimately underwent graft explantation or sacotomy with oversewing of the endoleak source. Freedom from any endoleak-related reintervention was 57% at 1 year and 36% at 3 years. Freedom from open treatment was 93% at 1 year and 82% at 3 years. Of the 44 patients with ≥6-month follow-up, 39 (89%) achieved clinical success. However, only 11 patients (25%) achieved clinical success without any further reintervention, and 29 patients (66%) achieved clinical success without open treatment.

CONCLUSIONS

Despite high technical success, endoleak recurrence after T2EL treatment is common, and multiple interventions are often needed to stabilize aneurysm sac size in patients diagnosed with T2EL-associated sac growth. Notably, one in five patients treated for T2ELs was discovered, on further evaluation, to have proximal or distal seal zone loss that necessitated repair to achieve sac stability. Thus, thorough assessment of all endoleak types should be performed in patients with T2ELs associated with sac growth before T2EL treatment to ensure appropriate care and to minimize ineffective interventions.

Platelets reflect the fate of type II endoleak after endovascular aneurysm repair

OBJECTIVE

The management of type II endoleak (T2E) remains controversial because of the heterogeneous outcome. For blood-based screening to detect malignant T2E, we focused on platelets after endovascular aneurysm repair (EVAR) and compared them with the prognosis of T2Es.

METHODS

From 2007 to 2015, there were 249 patients treated with EVAR for abdominal aortic aneurysm who were evaluated retrospectively. The mean follow-up period was 3.5 ± 0.2 years. T2Es that had aneurysm sac enlargement or converted to type I or type III endoleak were defined as malignant; the other T2Es were considered benign. Cases without any complications, including T2E, were defined as completed. We compared the platelet count on postoperative days (PODs) 1 to 7 with preoperative baseline values among the three groups. Sequentially, we calculated the cutoff of the platelet ratio on POD 7 to the baseline value in relation to malignant T2E using receiver operating characteristic analysis, and the cutoff ratio was 113% (sensitivity, 79%; specificity, 58%). We then reclassified T2E patients into T2E-high platelet (T2E-HP; ≥113%) or T2E-low platelet (T2E-LP; <113%) groups. The influence of platelets on T2E was evaluated with reintervention rate and cumulative aneurysm sac enlargement rate using the Kaplan-Meier method.

RESULTS

T2Es were found in 70 patients (28%), and 179 patients were assigned to the completed group. Malignant and benign T2Es were found in 33 and 37 patients, respectively. No difference was found in the preoperative baseline values. On POD 7, the platelet count in the malignant T2E group was significantly lower than that in the completed and benign T2E groups (168 × 10³/μL vs 207 × 10³/μL and 201 × 10³/μL; P = .0124). Then, 27 and 43 patients were assigned to the T2E-HP and T2E-LP groups, respectively. The reintervention-free survival rate in the T2E-LP group was lower than that in the completed group (at 3 years, 66.4% ± 8.0% vs 71.9% ± 4.0%; P = .0031). Among T2E patients, the cumulative aneurysm sac enlargement rates in the T2E-LP group were significantly higher than those in the T2E-HP group (at 3 years, 34.6% ± 8.2% vs 20.6% ± 8.2%; P = .0105). Univariate Cox proportional hazards analysis for the cumulative aneurysm sac enlargement rates among T2E patients showed that sex, dual antiplatelet therapy, and lower platelet ratio (<113%) were significant predictors; multivariate analysis showed that T2E-LP was the only significant predictor (hazard ratio, 2.60; P = .0355).

CONCLUSIONS

The platelet count of patients with malignant T2Es on POD 7 was definitively lower than that of patients with completed EVAR or with benign T2Es. The lower platelet count on POD 7 could be a risk factor for aneurysm sac enlargement among patients with T2Es.