Nikolaos Schoretsanitis

The Hemodynamic Impact of Misalignment of Fenestrated Endografts: A Computational Study☆

OBJECTIVE The hemodynamic consequences of misaligned stent-grafts (SG) in fenestrated endografts (EG) have not been adequately studied. Our aim was to study the hemodynamic effects of positional variations of SG, investigating the potential influence on the total displacement forces acting on the EG and the shear stress values at the stented segments. METHODS This was a computational study. An idealized EG model with two renal fenestrations was computationally reconstructed and centrally extended up to the suprarenal level to treat a suprarenal aneurysm. The misalignment of SG was represented by a variable take-off angle between the SG and the EG centerline axis, corresponding to angles of 90°, 176°, 142°, 38°, and 4°, respectively. Accordingly, the maximum EG displacement forces and the shear stress within the stented segments were calculated, using commercially available software. RESULTS The variable positions of the SG caused no effect on the maximum displacement force acting on the EG, being quite steady and equal to 5.55 N. On the contrary, the values of maximum shear stress acting on the stented segments were influenced by their orientation. The narrow transition zone between the distal end of the mating stent and the target artery showed higher stresses than any other segment. The right-angle take off SG position (90°) was associated with the lowest stresses (12.5 Pa), whereas the highest values were detected at 38° and 142° (16.5 and 16.1 Pa, respectively). The vessel segments distal to the SG exhibited constantly lower stress values (1.9-2.2 Pa) than any other segment. CONCLUSION We detected differences in the values of shear stress exerted on the stented arteries, depending on different positions that SG can adapt after the deployment of fenestrated EG. The pathophysiologic implication of our findings and their potential association with clinical events deserve further investigation and clinical validation.

Geometrical Factors Influencing the Hemodynamic Behavior of the AAA Stent Grafts: Essentials for the Clinician

Endovascular aneurysm repair (EVAR) is considered to be the treatment of choice for abdominal aortic aneurysms (AAA). Despite the initial technical success, EVAR is amenable to early and late complications, among which the migration of the endograft (EG) with subsequent proximal endoleak (Type Ia) leads to repressurization of the AAA sac, exposure to excessive wall stress, and, hence, to potential rupture. This article discusses the influence that certain geometrical factors, such as neck angulation, iliac bifurcation, EG curvature, neck-to-iliac diameter, and length ratios, as well as iliac limbs configuration can exert on the hemodynamic behavior of the EGs. The information provided could help both clinicians and EG manufacturers towards further development and improvement of EG designs and better operational planning.

Clinical Outcomes After Crossed-Limb vs. Conventional Endograft Configuration in Endovascular AAA Repair

Purpose: To report a case controlled analysis of endovascular aneurysm repair (EVAR) outcomes using the crossed-limb (CxL) endovascular configuration vs. the straight-limb configuration (SLC). Methods: From January 2007 to July 2012, 27 patients (25 men; mean age 73.7±7.2 years, range 53–82) were treated by EVAR with the CxL technique. These patients were matched anatomically with 27 patients (27 men; mean age 72.4±7.4 years, range 52–86) who underwent EVAR using the same endograft and the standard SLC within a ±6-month period. Primary outcome measures included technical and clinical success and freedom from graft limb thrombosis, any type of endoleak, early or late secondary interventions, and aneurysm-related death estimated using the Kaplan-Meier method. Results: The median follow-up periods for the CxL and SLC groups were 29.9 (range 6–54) and 33.5 (range 6–59) months, respectively (p=0.81). The technical success rate was 100% in both groups, but mean procedure times were significantly longer in the CxL group (116.3 vs. 90.7 minutes, p=0.035). Twelve intraoperative endoleaks (3 each for types Ia, Ib, II, and IV) occurred but without any difference between groups (p=0.51). One CxL group patient died in the early postoperative period (aneurysm-related) and another had an early graft limb thrombosis. One late type Ib intraoperative endoleak was recorded in the SLC group (p=0.51). For the CxL vs. SLC groups, the 1-year rates for freedom from endograft limb thrombosis (94% vs. 96%), any type of endoleak (96% vs. 96%), early or late reintervention (94% vs. 96%), and aneurysm-related death (94% vs. 96%) were not significantly different. Respective values at 36 months were 82% vs. 82%, 85% vs. 84%, 81% vs. 78%, and 83% vs. 84% (p>0.05). Clinical success rates at 12 months for the CxL and SLC groups were 91% and 100% (p>0.05), respectively, whereas at 36 months, the rates were 83% and 90% (p>0.05). Conclusion: No difference was found between the crossed-limb technique and the conventional endograft position as regards short- or midterm clinical outcomes.

Expanding Current EVAR Indications to Include Small Abdominal Aortic Aneurysms: A Glimpse of the Future:

The traditional criterion of maximum transverse diameter is not sufficient to differentiate the small abdominal aortic aneurysms (AAAs) that are either prone to rupture or prone to enlarge rapidly. Wall stress may be a more reliable indicator with respect to these tasks. We review the importance of geometric features in rupture- or growth-predictive models and stress the need for further evaluation and validation of geometric indices. This study may lead to identifying those small AAAs that could justify early endovascular intervention.

Hybrid Revascularization Procedures in Acute Limb Ischemia

BACKGROUND Although the clinical efficacy of hybrid procedures in patients with chronic limb ischemia has been well reported in the literature, sufficient evidence is lacking in the acute setting. Our aim was to evaluate the immediate and midterm clinical results on 28 patients with acute lower limb ischemia treated with hybrid reconstructions on emergent basis, from January 2010 to March 2013 in our tertiary referral vascular center. METHODS A total of 28 patients (31 operated limbs) underwent emergent hybrid revascularization, with endovascular treatment performed proximally or distally to the site of open reconstruction. The median follow-up period was 6 months (range: 1-26). The immediate technical success was clinically and hemodynamically evaluated with an ankle brachial pressure index (ABPI) measurement. Six-month overall patency, limb salvage, and survival rate were also estimated. All analyses were performed with Kaplan-Meier life table method, using the STATISTICA 7.0 statistical program. RESULTS Twenty-seven patients presented with grade IIb and 1 with grade III ischemia, respectively. Technical success was achieved in all patients, whereas hemodynamic improvement rate was achieved in 98%. ABPI preoperatively was increased from 0.14 ± 0.1 to 0.69 ± 0.28 postoperatively (P < 0.05). Perioperative morbidity and mortality rates were 21% and 11% respectively. Six-month overall patency, limb salvage, and survival rate were 86%, 92%, and 79%, respectively. CONCLUSIONS Hybrid revascularization in immediately threatened limbs provides an effective and durable option with acceptable mortality and amputation rate in these high-risk patients. These findings should be further confirmed by larger scale clinical studies.

Composite PTFE-transposed superficial femoral vein for lower limb arteriovenous access

Purpose We report our experience in creating a composite loop of transposed superficial femoral vein (tSFV) and polytetrafluoroethylene (PTFE) synthetic graft for lower limb access. The indication for surgery was exhaustion of access sites in both upper limbs. Methods Surgery was performed on 3 male patients. All patients had an ankle brachial index ≥0.9. The SFV was mobilized up to adductor canal, with ligation of all small tributary branches, up to the level below the profunda femoral vein, then tunneled medially to the skin. A 6–mm PTFE graft was tunneled laterally, deep in the subcutaneous plane in loop fashion to the end of the tSFV, where a beveled end-to-end anastomosis was created. Results The blood flow in both fistulas increased gradually to 0.7–1.3 l/min postoperatively. No clinical manifestation indicative of lower limb ischemia, lymphorrhea, or infection was documented. No signs related to chronic venous hypertension were noticed. Conclusions Our initial experience shows that the creation of a composite PTFE-tSFV conduit is a promising technique, since it can be constructed without compromising the distal perfusion, and without infectious complications.

Preemptive open surgical vs. endovascular repair for juxta-anastomotic stenoses of autogenous AV fistulae: a meta-analysis.

Purpose There is controversy about the best mode of preemptive repair of juxta-anastomotic stenoses in radial-cephalic arteriovenous fistula (AVFs). The aim of the present review was to compare the outcome of surgical vs. endovascular repair of those AVF stenoses. Methods A systematic review and meta-analysis was performed for studies comparing the outcome of open surgical vs. endovascular preemptive repair of AVF stenoses located in the juxta-anastomotic region. A search was carried out in April 2015. The analyzed outcome measures were the primary patency at 12 and 18 months and the assisted primary patency at 24 months. In addition, assessment of the methodological quality of the included studies was carried out. Results Four non-randomized cohort studies (297 patients) were analyzed. A random effects model was used to pool the data. The pooled odds ratio (OR and 95% confidence intervals) for the primary patency at 12 and at 18 months was 0.42 (0.25-0.72) and 0.33 (0.2-0.56), respectively, showing statistically significant higher patency of the surgically repaired group. The pooled OR for the assisted primary patency at 24 months was 0.53 (0.28-0.98) also in favor of the surgically repaired group (p<0.04) Conclusions The available evidence, based on non-randomized cohort studies, suggests that surgery is the best way to treat ‘juxta-anastomotic’ stenotic lesions in distal radial-cephalic AVFs, although angioplasty remains a valuable but less durable option in this location of the stenosis.

Extra- and intrathoracic access

The most complex patients requiring vascular access are those with bilateral central vein occlusions. Endovascular repair of the central lesions when feasible allow upper extremity use for access. When endovascular repair is not feasible, femoral vein transposition should be the next choice. When lower limb access sites have been exhausted or are contraindicated as in obese patients and in patients with peripheral arterial obstructive disease, a range of extrathoracic “exotic” extra-anatomic access procedures as the necklace cross-chest arteriovenous (AV) grafts, the ipsilateral axillo-axillary loops, the brachial-jugular AV grafts, the axillo-femoral AV grafts or even intra-thoracic ones as the right atrial AV bypasses represent the vascular surgeons last resort. The selection among those extra-anatomical chest-wall procedures should be based upon each patients anatomy or patient-specific factors.

A critical appraisal of endovascular stent-grafts in the management of abdominal aortic aneurysms

Endovascular repair of abdominal aortic aneurysms has widely replaced the open surgical repair due to its minimal invasive nature and the accompanying lower perioperative mortality and morbidity. During the past two decades, certain improvements and developments have provided a wide variety of endograft structural designs and geometric patterns, enabling the physician to approach a more patient-specific treatment of AAA. This review presents the currently available aortic endografts and describes the clinical, technical and mechanical characteristics of them.

Early Results of the Bolton Treovance Endograft in the Treatment of Abdominal Aortic Aneurysms

Purpose: To present early results with the Treovance aortic stent-graft in the treatment of abdominal aortic aneurysms (AAAs). Methods: Between October 2013 and January 2016, 35 consecutive AAA patients (mean age 74±7.7 years; 32 men) were treated with Treovance. The maximum diameter of the treated AAA was 60±9 cm. Nine (25%) patients presented with concomitant iliac aneurysms. Seven (20%) AAAs had infrarenal neck angulation >60°. The infrarenal neck length and diameter were 21.6±12.6 mm and 25.7±4.6 mm, respectively. Sixteen (45%) AAAs had a reversed tapered neck contour. Six (17%) and 9 (25%) patients showed severe or moderate iliac tortuosity, respectively. Primary endpoints were endoleak, reintervention, and aneurysm-related death. Results: Primary technical success was 94% due to 2 intraoperative type Ia endoleaks, which were successfully treated with a proximal aortic extension (100% assisted primary technical success). Local dissection was encountered in 5 (7%) of 70 femoral artery access sites in 4 patients. During a mean 12-month follow-up (range 6–24), clinical success was 97%. No type I or III endoleak, death, AAA rupture, open conversion, or device-related serious adverse events were documented. Four type II endoleaks were detected; one resolved spontaneously at 12 months and 2 remained stable, while one associated with AAA sac enlargement was treated successfully with embolization of the lumbar arteries (3% reintervention rate). Conclusion: Treovance shows accurate deployment even through angulated and tortuous iliac vessels and presents satisfactory conformability in highly angulated necks with acceptable clinical results. Future development to lower the profile and increase the flexibility of its delivery system will enhance its applicability in cases of narrow access vessels.