Efstratios Georgakarakos

Endovascular repair for ruptured abdominal aortic aneurysm confers an early survival benefit over open repair

BACKGROUND Despite the intuitive advantages of endovascular repair (EVAR) of ruptured abdominal aortic aneurysms (AAAs), uncertainty remains about the optimal management in the absence of convincing high-quality evidence. Our objective was to undertake a comprehensive literature review and perform a meta-analysis of outcome data of treatment modalities for ruptured AAAs. METHODS Systematic searches were conducted of electronic information sources to identify studies comparing perioperative outcomes of EVAR and open repair for AAA rupture. Summary estimates of odds ratios (ORs) or standardized mean difference and 95% confidence intervals (CIs) were obtained with a random-effects model. Meta-regression models were formed to explore potential heterogeneity as a result of changes in practice over time. RESULTS We selected 41 studies for analysis. The entire meta-analysis population comprised 59,941 patients (8201 EVAR patients and 51,740 open repair patients). EVAR was associated with a significantly lower incidence of in-hospital mortality (OR, 0.56; 95% CI, 0.50-0.64; P < .01; meta-analysis of risk-adjusted observational studies and randomized controlled trials: OR, 0.58; 95% CI, 0.46-0.73; P < .01). EVAR patients had a significantly decreased risk of developing respiratory complications (OR, 0.59; 95% CI, 0.49-0.69; P < .01) and acute renal failure (OR, 0.65; 95% CI, 0.55-0.78; P < .01) and a trend toward a reduced incidence of cardiac complications (OR, -0.02; 95% CI, -0.03 to 0.00; P = .05) and mesenteric ischemia (OR, 0.66; 95% CI, 0.44-1.00; P = .05). Patients treated with EVAR had significantly less requirements of intraoperative blood transfusion (standardized mean difference, -0.88; 95% CI, -1.06 to -0.70; P < .01). Random-effects meta-regression revealed no statistical evidence for an association between death and year of publication (P = .19). CONCLUSIONS Our analysis provides evidence to motivate the adoption of an EVAR-first policy in a nonelective setting and the establishment of standardized protocols for the management ruptured AAAs.

Computational Evaluation of Aortic Aneurysm Rupture Risk: What Have We Learned So Far?

In current clinical practice, aneurysm diameter is one of the primary criteria used to decide when to treat a patient with an abdominal aortic aneurysm (AAA). It has been shown that simple association of aneurysm diameter with the probability of rupture is not sufficient, and other parameters may also play a role in causing or predisposing to AAA rupture. Peak wall stress (PWS), intraluminal thrombus (ILT), and AAA wall mechanics are the factors most implicated with rupture risk and have been studied by computational risk evaluation techniques. The objective of this review is to examine these factors that have been found to influence AAA rupture. The prediction rate of rupture among computational models depends on the level of model complexity and the predictive value of the biomechanical parameters used to assess risk, such as PWS, distribution of ILT, wall strength, and the site of rupture. There is a need for simpler geometric analogues, including geometric parameters (e.g., lumen tortuosity and neck length and angulation) that correlate well with PWS, conjugated with clinical risk factors for constructing rupture risk predictive models. Such models should be supported by novel imaging techniques to provide the required patient-specific data and validated through large, prospective clinical trials.

A meta-analysis of outcome after percutaneous endovascular aortic aneurysm repair using different size sheaths or endograft delivery systems

Purpose To determine via a meta-analysis if the success rates for percutaneous EVAR using the “preclose” technique with suture-mediated vascular closure devices (SMCDs) are higher for smaller sheaths [≤18-F outer diameter (OD)] than for larger sheaths (≥20-F). Methods All English-language studies on percutaneous EVAR outcomes related to sheath sizes published between 1999 and August 30, 2010, were searched using MEDLINE and SCOPUS. Randomized trials, retrospective or prospective observational studies, and original articles (including a review) were included. The search identified 32 relevant full-text studies; data on percutaneous EVAR outcomes per sheath size category (≤18-F and ≥20-F OD) were included in the final meta-analysis of data from 17 studies (1 randomized controlled trial and 8 retrospective and 8 prospective cohort observational studies). The final analysis included 1440 patients and 2447 femoral access sites. Primary success was defined as closure of a common femoral artery arteriotomy without the need for any adjunctive surgical or endovascular procedure. Results Pooled data revealed that success rates were significantly better when percutaneous EVAR was performed with ≤18-F sheaths than with ≥20-F sheaths (odds ratio 1.78, 95% confidence interval 1.24 to 2.54, p=0.002). This benefit, although not significant, was more pronounced when multiple rather than single pre-applied SMCDs were deployed (odds ratio 2.16 vs. 1.64, respectively; p=0.353). Conclusion When considering primary success, it appears that larger-bore femoral access sheaths (≥20-F) introduced for percutaneous EVAR after pre-application of SMCDs are predictors of primary failure and the need for conversion to a femoral cutdown. More advanced large-bore SMCDs are required to further reduce the necessity for conversion. Planned use of multiple SMCDs might be more beneficial when ≤18-F sheaths are required.

Meta-analysis and Meta-Regression Analysis of Outcomes of Carotid Endarterectomy and Stenting in the Elderly

IMPORTANCE Uncertainty exists about the influence of advanced age on the outcomes of carotid revascularization. OBJECTIVE To undertake a comprehensive review of the literature and conduct an analysis of the outcomes of carotid interventions in the elderly. DESIGN AND SETTING A systematic literature review was conducted to identify articles comparing early outcomes of carotid endarterectomy (CEA) or carotid stenting (CAS) in elderly and young patients. MAIN OUTCOMES AND MEASURES Combined overall effect sizes were calculated using fixed or random effects models. Meta-regression models were formed to explore potential heterogeneity as a result of changes in practice over time. RESULTS Our analysis comprised 44 studies reporting data on 512,685 CEA and 75,201 CAS procedures. Carotid stenting was associated with increased incidence of stroke in elderly patients compared with their young counterparts (odds ratio [OR], 1.56; 95% CI, 1.40-1.75), whereas CEA had equivalent cerebrovascular outcomes in old and young age groups (OR, 0.94; 95% CI, 0.88-0.99). Carotid stenting had similar peri-interventional mortality risks in old and young patients (OR, 0.86; 95% CI, 0.72-1.03), whereas CEA was associated with heightened mortality in elderly patients (OR, 1.62; 95% CI, 1.47-1.77). The incidence of myocardial infarction was increased in patients of advanced age in both CEA and CAS (OR, 1.64; 95% CI, 1.57-1.72 and OR, 1.30; 95% CI, 1.16-1.45, respectively). Meta-regression analyses revealed a significant effect of publication date on peri-interventional stroke (P = .003) and mortality (P < .001) in CAS. CONCLUSIONS AND RELEVANCE Age should be considered when planning a carotid intervention. Carotid stenting has an increased risk of adverse cerebrovascular events in elderly patients but mortality equivalent to younger patients. Carotid endarterectomy is associated with similar neurologic outcomes in elderly and young patients, at the expense of increased mortality.

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.

Aneurysm sac shrinkage after endovascular treatment of the aorta: Beyond sac pressure and endoleaks

The isolation of the aneurysm sac from systemic pressure and its consequent shrinkage are considered criteria of success after endovascular repair (EVAR). However, the process of shrinkage does not solely depend on the intrasac pressure, the predictive role of which remains ambiguous. This brief review summarizes the additional pathophysiological mechanisms that regulate the biomechanical properties of the aneurysm wall and may interfere with the process of aneurysm sac shrinkage.

Clopidogrel Load for Emboli Reduction in Patients With Symptomatic Carotid Stenosis Undergoing Urgent Carotid Endarterectomy

Background and Purpose— Microembolic signals (MES) on transcranial Doppler are an independent risk factor for recurrent stroke in patients with extracranial symptomatic/asymptomatic carotid artery stenosis (CARAS). Clopidogrel load (300 mg) combined with dual antiplatelet therapy has been shown to reduce MES in patients with symptomatic CARAS. We sought to determine feasibility of clopidogrel load in decreasing asymptomatic embolization in patients with symptomatic CARAS undergoing urgent carotid endarterectomy within the first 2 weeks from the index event. Subjects and Methods— Consecutive patients with symptomatic CARAS (70%–99%) and presence of MES on 1-hour baseline (<24 hours from the index event) transcranial Doppler monitoring of ipsilateral middle cerebral artery were treated with clopidogrel load followed by clopidogrel (75 mg)±aspirin (100 mg) during the elapsed time period between hospital admission and urgent carotid endarterectomy at 3 tertiary-care stroke centers. Repeat 1-hour transcranial Doppler monitoring was performed the day before surgery. Bleeding complications during surgery and recurrent strokes or transient ischemic attacks during the first month of ictus were prospectively recorded. Results— A total of 11 symptomatic CARAS patients (mean age, 66±7 years; 73% men; 64% acute ischemic strokes) were treated with clopidogrel load followed by dual (67%) or single (33%) antiplatelet therapy. MES count was significantly reduced between baseline (median count, 8 MES/h; interquartile range, 6–19) and repeat transcranial Doppler monitoring (0 MES/h; interquartile range, 0–3; P=0.003). No bleeding complications, recurrent strokes, or transient ischemic attacks were documented. Conclusions— Our pilot observational study provides preliminary nonrandomized data regarding the potential efficacy of clopidogrel load to reduce asymptomatic embolization in patients with symptomatic CARAS before urgent carotid endarterectomy.

The ovation abdominal stent graft for the treatment of abdominal aortic aneurysms: current evidence and future perspectives

ABSTRACT The Ovation Abdominal Stent Graft System is a trimodular endoprosthesis recently introduced for the endovascular repair of abdominal aortic aneurysm (AAA). It uncouples the stages of stent-graft fixation and sealing with the suprarenal fixation achieved with a long, rigid anchored stent while the sealing onto the neck is accomplished via a pair of polymer-filled inflatable rings that accommodate to each patient’s individual anatomy. Moreover, the lack of Nitinol support enables lower profiles of the endograft’s delivery system, thus facilitating the navigation through angulated and stenosed iliac vessels. Ovation’s novel design expands further the AAA eligibility to endovascular repair. This article discusses the clinical and hemodynamic consequences of the Ovation design and contributes to better understanding of current and future implications.

Training to measure ankle-brachial index at the undergraduate level: can it be successful?

We examined the effectiveness of teaching ankle–brachial index (ABI) measurement to medical students. ABI was estimated in 28 lower limbs by an experienced vascular surgeon. After a 2-week training course, 5 fourth-year students repeated the estimations and their results were compared with that of the trainer’s. There was no difference in ABI values between trainees and trainer for subjects with mild-to-moderate peripheral arterial disease (PAD; 0.77 ± 0.22 vs 0.77 ± 0.19, respectively, P = .95). In the 4 normal limbs, ABI was 1.37 ± 0.12 and 1.16 ± 0.11, as measured by the trainer and the trainees, respectively (P < .00001). In subjects with severe PAD, trainees tended to overestimate ABI (P = .0002) in the beginning of the educational process, but this was no longer the case at a later stage of the training with no difference in ABI values between the 2 examiner groups (P = .09). In conclusion, training of medical students in ABI measurement can be helpful toward accurate estimation of PAD and merits further practice.

An overview of the hemodynamic aspects of the blood flow in the venous outflow tract of the arteriovenous fistula

Upper limb vein aneurysms complicate all types of autogenous arteriovenous fistulae (AVF) and comprise false aneurysms secondary to venipuncture trauma as well as true aneurysms, characterized by dilatation of native veins. The dilatation of a normal vein and the development of a true aneurysm are strongly influenced by local hemodynamic factors affecting the flow in the drainage venous system and are also the target of operative interventions. This review article focuses on the description of these hemodynamic aspects which all physicians involved in the management of dialysis patients should be aware of. Furthermore, it delineates their complicated interactions and also highlights their utility in clinical decision-making and therapeutic management.