[Nellix® endovascular aneurysm sealing (EVAS) - a new technology for endovascular management of infrarenal aortic aneurysms]

BACKGROUND

Recently used endografts for envascular aneurysm repair (EVAR) exclude the pathology by fixation at both the proximal and distal landing zone. Due to endoleaks and migration EVAR is associated with a relevant rate of secondary interventions. The Nellix® system (Endologix Inc., CA, USA) was developed to seal the complete aneurysm using a polymer filling, therefore stabilising endograft-position and reducing the rate of endoleaks and reinterventions. The present contribution introduces the method, describes the technique of implantation and presents the first clinical results. Material und Methods: The Nellix system consists of two balloon-expandable stent grafts made of a cobalt-chromium composition, surrounded with ePTFE and the so-called endobags. During the implantation each endobag is filled with a non-biodegradable polymer, sealing the aneurysm lumina including the proximal and distal landing zone. Hence, lumbar arteries will be sealed to reduce the probability of a type II endoleak.

RESULTS

Longterm durability as well as the structural integrity of the Nellix system has been proven over 4 years in sheep experiments. The technical success in a multicentre, prospective registry was 94% without the appearance of severe adverse events (migration, occlusion, secondary endoleak).

CONCLUSION

EVAS is a new and different concept of endovascular AAA repair. Recent clinical data of the Nellix system are promising showing a high technical success rate while the need for secondary intervention is low. Further studies in larger cohorts are needed.

State-of-the-art aortic imaging: Part II - applications in transcatheter aortic valve replacement and endovascular aortic aneurysm repair

Transcatheter aortic valve replacement (TAVR) as well as thoracic and abdominal endovascular aortic repair (TEVAR and EVAR) rely on accurate pre- and postprocedural imaging. This review article discusses the application of imaging, including preprocedural assessment and measurements as well as postprocedural imaging of complications. Furthermore, the exciting perspective of computational fluid dynamics (CFD) based on cross-sectional imaging is presented. TAVR is a minimally invasive alternative for treatment of aortic valve stenosis in patients with high age and multiple comorbidities who cannot undergo traditional open surgical repair. Given the lack of direct visualization during the procedure, pre- and peri-procedural imaging forms an essential part of the intervention. Computed tomography angiography (CTA) is the imaging modality of choice for preprocedural planning. Routine postprocedural follow-up is performed by echocardiography to confirm treatment success and detect complications. EVAR and TEVAR are minimally invasive alternatives to open surgical repair of aortic pathologies. CTA constitutes the preferred imaging modality for both preoperative planning and postoperative follow-up including detection of endoleaks. Magnetic resonance imaging is an excellent alternative to CT for postoperative follow-up, and is especially beneficial for younger patients given the lack of radiation. Ultrasound is applied in screening and postoperative follow-up of abdominal aortic aneurysms, but cross-sectional imaging is required once abnormalities are detected. Contrast-enhanced ultrasound may be as sensitive as CTA in detecting endoleaks.

State-of-the-art aortic imaging: Part I - fundamentals and perspectives of CT and MRI

Over the last two decades, imaging of the aorta has undergone a clinically relevant change. As part of the change non-invasive imaging techniques have replaced invasive intra-arterial digital subtraction angiography as the former imaging gold standard for aortic diseases. Computed tomography (CT) and magnetic resonance imaging (MRI) constitute the backbone of pre- and postoperative aortic imaging because they allow for imaging of the entire aorta and its branches. The first part of this review article describes the imaging principles of CT and MRI with regard to aortic disease, shows how both technologies can be applied in every day clinical practice, offering exciting perspectives. Recent CT scanner generations deliver excellent image quality with a high spatial and temporal resolution. Technical developments have resulted in CT scan performed within a few seconds for the entire aorta. Therefore, CT angiography (CTA) is the imaging technology of choice for evaluating acute aortic syndromes, for diagnosis of most aortic pathologies, preoperative planning and postoperative follow-up after endovascular aortic repair. However, radiation dose and the risk of contrast induced nephropathy are major downsides of CTA. Optimisation of scan protocols and contrast media administration can help to reduce the required radiation dose and contrast media. MR angiography (MRA) is an excellent alternative to CTA for both diagnosis of aortic pathologies and postoperative follow-up. The lack of radiation is particularly beneficial for younger patients. A potential side effect of gadolinium contrast agents is nephrogenic systemic fibrosis (NSF). In patients with high risk of NSF unenhanced MRA can be performed with both ECG- and breath-gating techniques. Additionally, MRI provides the possibility to visualise and measure both dynamic and flow information.

Computational fluid dynamics investigation of chronic aortic dissection hemodynamics versus normal aorta

OBJECTIVES

To evaluate hemodynamic changes during aneurysmal dilatation in chronic type B aortic dissections compared to hemodynamic parameters in the healthy aorta with the use of computational fluid dynamics (CFD).

METHODS

True lumen (TL)/false lumen (FL) dimensional changes, changes in total pressure (TP), and wall shear stress (WSS) were evaluated at follow-up (FU) compared to initial examination (IE) with transient CFD simulation with geometries derived from clinical image data and inflow boundary conditions from magnetic resonance images. The TL/FL pressure gradient between ascending and descending aorta (DAo) and maximum WSS at the site of largest dilatation was compared to values for the healthy aorta.

RESULTS

Hemodynamic changes at site of largest FL dilatation included 77% WSS reduction and 69% TP reduction. Compared to the healthy aorta, pressure gradient between ascending and DAo was a factor of 1.4 higher in the TL and a factor of 1.5 in the FL and increased at FU (1.6 and 1.7, respectively). Maximum WSS at the site of largest dilatation was a factor of 3 lower than that for the healthy aorta at IE and decreased by more than a factor of 2 at FU.

CONCLUSIONS

The FL dilatation at FU favorably reduced TP. In contrast, unfavorable increase in pressure gradient between ascending and DAo was observed with higher values than in the healthy aorta. Maximum WSS was reduced at the site of largest dilation compared to healthy aorta.

Clinical significance of type II endoleaks after thoracic endovascular aortic repair

BACKGROUND

To evaluate the clinical significance of type II endoleaks (ELII) after thoracic endovascular aortic repair (TEVAR).

METHODS

From January 1997 to June 2012, a total of 344 patients received TEVAR in our institution. ELII was diagnosed in 30 patients (8.7%; 13 males; median age: 65 years, range: 24 to 84 years), representing the study population of this retrospective, single-center analysis. Mean follow-up was 29.5 months (range, 8 months to 9.5 years).

RESULTS

Primary ELII was observed in all but two cases (28/30; 93.3%). The most common sources of ELII were the left subclavian artery (LSA; 13/30; 43.3%) and intercostal/bronchial vessels (13/30; 43.3%), followed by visceral arteries (4/30; 13.4%). Overall mortality was 33.3% (10/30). ELII-related death (secondary rupture) was observed in 20% (2/10). Reintervention (RI) procedures for ELII were performed in 9 of 30 patients (30.0%); 5 of 9 (55.6%) in cases with ELII via the LSA. Indications for RI were diameter expansion in five and extensive leakage in four cases. Treatment was successful in five patients (55.6%) but failed in four cases (44.4%). In 12 of 21 (57.1%) untreated patients, ELII sealed during follow-up. In conservatively treated patients, an increase in aortic diameter has been only observed in a patient with secondary ELII.

CONCLUSIONS

The results presented herein suggest that the clinical impact of ELII after TEVAR must not be underestimated. Albeit a transient finding in most cases, ELII is associated with a relevant RI rate, particularly in cases involving the LSA. RI seems indicated in patients with increasing aortic diameter and/or extensive leakage. Careful surveillance of all patients with ELII is recommended.

[Endovascular therapy of para-anastomotic aneurysms of the aorta. Technical options]

BACKGROUND

Open repair of para-anastomotic aneurysms (pAAA) after conventional aortoiliac repair is associated with a high perioperative mortality and morbidity. Endovascular treatment options have evolved over the last decade. The aim of this article is to demonstrate and review these endovascular strategies.

MATERIAL AND METHODS

Between 01/2009 and 06/2012, a total of 12 patients received endovascular treatment for proximal (n = 7) or distal (n = 5) pAAA (n = 2 contained rupture). A retrospective analysis of these patients was performed. Median age was 71.5 years (range 55-87 years). The median time interval between primary operation and endovascular repair of the pAAA was 15 years (range 1-31 years) and median follow-up was 1.3 years (range 0 days - 3 years). Endovascular exclusion of the pAAA was achieved by implantation of an aortouniiliac endograft (n = 6), chimney graft (n = 1), fenestrated endograft (n = 2) and iliac extension (n = 3).

RESULTS

Technical success could be achieved in all patients and in-hospital mortality was 16.8  % (n = 2). No patient required a reintervention but during follow-up one additional patient died due to gastrointestinal bleeding. No primary or secondary type I/III endoleaks were observed.

CONCLUSIONS

Despite a not negligible mortality rate endovascular treatment of para-anastomotic aneurysms and anastomotic pseudoaneurysms appears to be a safe alternative for conventional open repair.

Decision-making and techniques in hypogastric artery revascularization

The aim of this article was to describe and discuss the currently available endovascular and open surgical techniques to preserve or occlude the hypogastric artery during aortoiliac aneurysm repair and thus support the process of decision-making in hypogastric artery revascularization.

Accuracy and variability of semiautomatic centerline analysis versus manual aortic measurement techniques for TEVAR

OBJECTIVES

This study aims to test whether inter-observer variability and time of diameter measurements for thoracic endovascular aortic repair (TEVAR) are improved by semiautomatic centerline analysis compared to manual assessment.

METHODS

Preoperative computed tomography (CT) angiographies of 30 patients with thoracic aortic disease (mean age 66.8 ± 11.6 years, 23 males) were retrospectively analysed by two blinded experts in vascular radiology. Maximum aortic diameters at three positions relevant to TEVAR were assessed (P1, distal to left common carotid artery; P2, distal to left subclavian artery; and P3, proximal to coeliac trunk) using three measurement techniques: manual axial slices (axial), manual double-oblique multiplanar reformations (MPRs) and semiautomatic centerline analysis.

RESULTS

Diameter measurements by both centerline analysis and the axial technique did not significantly differ from MPR (p = 0.17 and p = 0.37). Total deviation index for 0.9 was for P1 2.7 mm (axial), 3.7 mm (MPR), 1.8 mm (centerline); for P2 2.0 mm (axial), 3.6 mm (MPR), 1.8 mm (centerline); and for P3 3.0 mm (axial), 3.5 mm (MPR), 2.5 mm (centerline). Measurement time using centerline analysis was significantly shorter than for assessment by MPR.

CONCLUSIONS

Centerline analysis provides the least variable and fast diameter measurements in TEVAR patients with the same accuracy as the current reference standard MPR.

Current clinical practice in postoperative endovascular aneurysm repair imaging surveillance

PURPOSE

To investigate the current clinical practice in postoperative endovascular aneurysm repair (EVAR) imaging surveillance.

MATERIALS AND METHODS

Corresponding authors of EVAR publications during the years 2006-2011 and subscribers to an endovascular journal were invited to complete a 27-question online survey related to institutional demographics, standard post-EVAR imaging surveillance, and imaging protocols in special circumstances (eg, renal insufficiency).

RESULTS

The survey was completed by 515 of 9,631 physicians performing EVAR from 52 countries. Of respondents, 65.3% were affiliated with experienced centers where EVAR has been performed for > 10 years or with > 50 EVAR procedures performed per year. Computed tomography (CT) angiography was the modality used most often for standard surveillance with a maximum time interval between studies of 12 months in 78.8% of centers out to 5 years. Experienced centers were more likely to delay follow-up imaging to 1 year after an unremarkable initial post-EVAR imaging study (P < .001), to extend surveillance intervals > 12 months (P = .043), and to use ultrasound (P < .01) for surveillance. After the detection of a type II endoleak, CT angiography was favored for follow-up by 59.4% of the respondents. Experienced centers were more likely to favor ultrasound (P = .006) and to schedule this follow-up examination later (after 6-12 months, P < .001). Of respondents, 62.8% used a glomerular filtration rate threshold of < 30 mL/min for not performing contrast-enhanced CT scan. In patients with renal insufficiency, most respondents performed ultrasound with or without a concomitant noncontrast CT scan.

CONCLUSIONS

CT is the most frequently used method of long-term surveillance after EVAR. Use of ultrasound for long-term surveillance, extension of follow-up time intervals, or both were most often reported in experienced centers.

Reproducibility of deriving parameters of AAA rupture risk from patient-specific 3D finite element models

PURPOSE

To assess the reproducibility of estimating biomechanical parameters of abdominal aortic aneurysms (AAA) based on finite element (FE) computations derived from a commercially available, semiautomatic vascular analyzer that reconstructs computed tomographic angiography (CTA) data into FE models.

METHODS

The CTA data from 10 consecutive male patients (mean age 74 years, range 63-87) with a fusiform infrarenal AAA >5 cm in diameter were used for this study, along with the CTA scans from 4 individuals without aortic disease. Three different observers used semiautomatic reconstruction software to create deformable contour models from axial CT scans. These 3-dimensional FE models captured the aortic wall and thrombus tissue using isotropic finite strain constitutive modeling. Geometric (maximum diameter and volume measurements based on an anatomical centerline) and biomechanical determinants [aneurysm peak wall stress (PWS) and the peak wall rupture risk (PWRR) index] were then calculated from the FE models. The determinations were made 5 times for each anonymized dataset presented for analysis in random order (5-fold measurements for 14 datasets produced 210 measurements from the 3 observers). Inter- and intraobserver variability were assessed by calculating the coefficient of variation of these repeated measures. The methodological variations were expressed with the intraclass correlation coefficient (ICC) and Bland-Altman plots.

RESULTS

The median segmentation time was < 1 hour (mean 39.2 minutes, range 25-48) for datasets from the AAA patients; for the healthy individuals, segmentation times were considerably shorter (median 8.7 minutes, range 4-15). Intraobserver reproducibility was high, as represented by a CV <3% for the diameter measurement and < 5.5% for volume, PWS, and the PWRR index. The ICC was 0.97 (range 0.95-0.98) for diameter and 0.98 (range 0.97-0.99) for volume; for PWS and the PWRR index, the ICCs were equal at 0.98 (range 0.97-0.99).

CONCLUSION

The reproducibility of volume and maximum diameter measurements in infrarenal AAAs with FE analysis is high. With the model used in this semiautomatic reconstruction software, wall stress analysis can be achieved with high agreement among observers and in serial measurements by a single observer.

Self-Expandable Stents in the Treatment of Acute Ischemic Stroke Refractory to Current Thrombectomy Devices

Background and Purpose—

Vessel recanalization is a strong predictor of good outcome in acute ischemic strokes (AIS) secondary to large vessel occlusions. We report our single-center experience with self-expandable stents in the treatment of AIS.

Methods—

The stroke database of Baptist Cardiac and Vascular Institute in Miami was retrospectively reviewed from August of 2008 to September of 2010. All cases of AIS in which a self-expandable stents was deployed as acute endovascular intervention were included in the analysis. Criteria for intervention were the onset of neurological symptoms because of AIS, a National Institute of Health Stroke Scale score ≥4 at presentation, stroke attributable to a large vessel occlusion, and failure of arterial thrombolysis or mechanical thrombectomy or both. Good outcome was defined as a modified Rankin Scale score ≤2 at 1 month from hospital discharge.

Results—

Nineteen patients with AIS who underwent stenting were identified. Median National Institute of Health Stroke Scale score on admission was 19. Six Enterprise and 13 Wingspan stents were deployed. Recanalization was achieved in 95% occlusions (63% thrombolysis in myocardial infarction grade 3 and 32% thrombolysis in myocardial infarction grade 2). Good clinical outcome was achieved in 42%. No intraprocedural complications occurred and all stents were successfully deployed. Symptomatic intracerebral hemorrhage occurred in 3 (16%) patients, 2 of whom died.

Conclusions—

Use of self-expandable stents in AIS appears to be safe and may be considered when currently available thrombectomy devices and/or intraarterial thrombolysis fail.

Aortic Aneurysm Pressure Sensors Can be of Value in the Acute Postoperative Setting

Purpose: To report on a case that demonstrates the use and current limits of abdominal aortic pressure sensor devices. Case report: An 83-year-old, high-risk patient underwent endovascular aortic repair (EVAR) of an infrarenal aortic aneurysm (maximum aneurysm diameter: 6.5 cm) with implantation of a pressure sensor device. At the end of the procedure and on the first postoperative day, the sensor detected persistent high pressures in the aneurysm sac, indicating an endoleak that could not be visualized on the intraoperative completion angiography but was confirmed on duplex ultrasound. During repeated angiography (postoperative day 6), again no endoleak could be detected, this time corresponding with the sensor reading that was unfortunately not interrogated again before the reintervention. Conclusion: Pressure sensor devices provide a useful, additional diagnostic tool in detecting and following endoleaks after EVAR and can help guide decisions regarding reinterventions.

Treatment of an asymptomatic penetrating aortic ulcer in a young patient

We want to report and discuss the indication for open surgery for an asymptomatic penetrating aortic ulcer (PAU) in the era of thoracic endovascular aortic repair (TEVAR). A 31-year-old female presented with the diagnosis of an aneurysm in the distal aortic arch. With respect to the patients young age, the controversial status of connective tissue disorders and in the absence of concomitant disease, open repair was indicated. There was no proof of a mycotic plaque or connective tissue disease in the microbiological-, pathological analysis and at electron-microscopy. The patient was discharged on the thirteenth postoperative day. In spite of good preliminary results of TEVAR in PAU, in selective cases there is still an indication for open surgery.

Endografting in the aortic arch - does the proximal landing zone influence outcome?

OBJECTIVES

To analyse early and midterm results of thoracic aortic endografting (TEVAR) in the aortic arch.

METHODS

Between January 1997 and February 2009 178 patients received TEVAR in the aortic arch at our institution. This population was subdivided into four groups according to the proximal landing zone (LZ) classification in the aortic arch by Ishimaru et al. and a retrospective analysis regarding perioperative mortality, morbidity and endoleak formation was performed.

RESULTS

The overall 30-day mortality rate was 14% with no statistical significant difference between LZ's 0-3 (p=0.274). Renal insufficiency (hazard ratio (HR) 2.5; p=0.0119), age >75 years (HR 3.1; p=0.0019) and emergency procedures (HR 8.9; p < 0.0001) were independent predictors of death. There was no significant difference regarding type I (p=0.07) or type III (p=0.49) endoleaks between the proximal LZs, but a significant difference regarding the development of type II endoleaks (p=0.01).

CONCLUSIONS

The present study showed no influence of the proximal LZ on perioperative mortality and morbidity rate. Furthermore it did not influence relevant (type I/III) endoleak formation.