Magnetic entropy table-like shape and enhancement of refrigerant capacity in La1.4Ca1.6Mn2O7-La1.3Eu0.1Ca1.6Mn2O7 composite.

In this work, we have investigated the structural, magnetic and magnetocaloric properties of La1.4Ca1.6Mn2O7 (A) and La1.3Eu0.1Ca1.6Mn2O7 (B) oxides. These compounds are synthesized by a solid-state reaction route and indexed with respect to Sr3Ti2O7-type perovskite with the I4/mmm space group. The substitution of La by 10% Eu enhances the value of magnetization and reduces the Curie temperature (T C). It is also shown that these compounds undergo a first-order ferromagnetic-paramagnetic phase transition around their respective T C. The investigated samples show large magnetic entropy change (ΔS M) produced by the sharp change of magnetization at their Curie temperatures. An asymmetric broadening of the maximum of ΔS M with increasing field is observed in both samples. This behaviour is due to the presence of metamagnetic transition. The ΔS M(T) is calculated for A x /B1-x composites with 0 ≤ x ≤ 1. The optimum ΔS M(T) of the composite with x = 0.48 approaches a nearly constant value showing a table-like behaviour under 5 T. To test these calculations experimentally, the composite with nominal composition A0.48/B0.52 is prepared by mixing both individual samples A and B. Magnetic measurements show that the composite exhibits two successive magnetic transitions and possesses a large MCE characterized by two ΔS M(T) peaks. A table-like magnetocaloric effect is observed and the result is found to be in good agreement with the calculations. The obtained ΔS M(T) is ≈4.07 J kg-1 K-1 in a field change of 0-5 T in a wide temperature span over ΔT FWHM ∼ 68.17 K, resulting in a large refrigerant capacity value of ≈232.85 J kg-1. The MCE in the A0.48/B0.52 has demonstrated that the use of composite increases the efficiency of magnetic cooling with µ 0 H = 5 T by 23.16%. The large ΔT FWHM and RC values together with the table-like (-ΔS M)max feature suggest that the A0.48/B0.52 composite can meet the requirements of several magnetic cooling composites based on the Ericsson-cycle. In addition, we show that the magnetic field dependence of MCE enables a clear analysis of the order of phase transition. The exponent N presents a maximum of N > 2 for A, B and A0.48/B0.52 samples confirming a first-order paramagnetic-ferromagnetic transition according to the quantitative criterion. The negative slope observed in the Arrott plots of the three compounds corroborates this criterion.

The Concept of Risk Assessment and Being Unfit for Surgery.

The concept of risk assessment and the identification of surgical unfitness for vascular intervention is a particularly controversial issue today as the minimally invasive surgical population has increased not only in volume but also in complexity (comorbidity profile) and age, requiring an improved pre-operative selection and definition of high risk. A practical step by step (three steps, two points for each) approach for surgical risk assessment is suggested in this review. As a general rule, the identification of a "high risk" patient for vascular surgery follows a step by step process where the risk is clearly defined, quantified (when too "high"?), and thereby stratified based on the procedure, the patient, and the hospital, with the aid of predictive risk scores. However, there is no standardized, updated, and objective definition for surgical unfitness today. The major gap in the current literature on the definition of high risk in vascular patients explains the lack of sound validated predictive systems and limited generalizability of risk scores in vascular surgery. In addition, the concept of fitness is an evolving tool and many traditional high risk criteria and definitions are no longer valid. Given the preventive purpose of most vascular procedures performed in elderly asymptomatic patients, the decision to pursue or withhold surgery requires realistic estimates not only regarding individual peri-operative mortality, but also life expectancy, healthcare priorities, and the patient's primary goals, such as prolongation of life versus maintenance of independence or symptom relief. The overall "frailty" and geriatric risk burden, such as cognitive, functional, social, and nutritional status, are variables that should be also included in the analyses for stratification of surgical risk in elderly vascular patients.

Arbitrary Palliation of Ruptured Abdominal Aortic Aneurysms in the Elderly is no Longer Warranted.

OBJECTIVE/BACKGROUND: A consistent number of elderly patients with ruptured abdominal aortic aneurysms (rAAAs) are deemed unfit for repair and excluded from any treatment. The objective of this study was to examine the impact on survival of endovascular repair and open surgery with restricted turndown in acute AAA repair. METHODS: A prospective database for patients treated for rAAA was established. None of the patients admitted alive with rAAA were denied treatment. Multivariate regression models, the predictive risk assessment Glasgow Aneurysm Score (GAS), and subgroup analyses in older patients were applied to identify indicators of excessive 30 day mortality risk that could affect the decision for turndown. RESULTS: From 2006 to 2015, 113 consecutive patients (93 males; mean age 77.2 years) with rAAAs were treated (69 open surgery; 44 EVAR). Overall peri-operative (30 day) mortality was 38.9% (44/113): 40.6% (28/69), and 36.4% (16/44) after open surgery and EVAR, respectively (p = .70). Multivariate logistic regression identified old age as an indicator of increased peri-operative mortality (odd ratio [OR] 1.2, 95% confidence interval [CI] 1.1-1.3; p = .001), as well as free aneurysm rupture (OR 5.0, 95% CI 1.3-19.9; p = .02). GAS was higher in patients who died (97.75 vs. 86.62), but the score failed to identify increased peri-operative mortality risk in adjusted analyses (OR 1.0; p = .06). Almost two thirds of the patients (n = 71) were older than 75 at the time of aneurysm rupture (48.6% octogenarians) and EVAR was more commonly applied than open surgery (86.4% vs. 47.8%; p < .0001). Peri-operative mortality in > 75 year old patients was 46.5% compared with 26.2% in younger patients (p = .05), with rates increased after open surgery (54.5% vs. 27.8%, p = .03) but not after EVAR (39.5% vs. 16.7%; p = .39). According to Kaplan-Meier estimates, mean survival was 39.7 ± 4.8 months. Patients older than 75 years of age survived for a mean of 23.0 ± 4.47 months after rupture. CONCLUSION: In this study aggressive treatment with a very restricted or no turndown strategy for any rAAA, also applied to older patients, allowed for an additional mean 40 months of survival after aneurysm rupture. In the contemporary endovascular era the decision to deny repair arbitrarily to older patients with rAAAs must be revisited.

Safety of chronic anticoagulation therapy after endovascular abdominal aneurysm repair (EVAR).

OBJECTIVE: Current data supporting the effect of anticoagulation drug use on aneurysm sealing and the durability of endovascular abdominal aneurysm repair (EVAR) are conflicting. This study assessed the safety of chronic anticoagulation therapy after EVAR. METHODS: Records of 1409 consecutive patients having elective EVAR during 1997-2011 who were prospectively followed were reviewed. Survival, reintervention, conversion, and endoleak rates were analyzed in patients with and without chronic anticoagulants. Cox proportional hazards models were used to estimate the effect of anticoagulation therapy on outcomes. RESULTS: One-hundred and three (7.3%) patients were on chronic anticoagulation drugs (80 on vitamin K antagonists) at the time of EVAR. An additional 46 patients started on anticoagulants after repair were identified. Patients on chronic anticoagulation therapy at repair (mean age 73.6 years; 91 males) had more frequent cardiac disease (74.8% vs. 44.2%; p < 00001), but no other differences in demographic and major baseline comorbidities with respect to the others. At baseline, mean abdominal aortic aneurysm (AAA) diameter was 56.43 mm vs. 54.65 mm (p = .076) and aortic neck length 26.54 mm vs. 25.21 mm (p = .26) in patients with and without anticoagulants, respectively. At 5 years, freedom from endoleak rates were 55.5% vs. 69.9% (p < .0001), and freedom from reintervention/conversion rates were 69.4% vs. 82.4% (p < .0001) in patients with (including those with delayed drug use) and without chronic anticoagulants, respectively. Controlling for covariates with the Cox regression method, at a mean follow-up of 64.3 ± 45.2 months after EVAR, use of anticoagulation drugs was independently associated with an increased risk of endoleak (odds ratio, OR 1.6; 95% confidence interval, CI: 1.23-2.07; p < .0001) and reintervention or late conversion rates (OR 1.8; 95% CI: 1.31-2.48; p < .0001). CONCLUSIONS: The safety of anticoagulation therapy after EVAR is debatable. Chronic anticoagulation drug use risks exposure to a poor long-term outcome. A critical and balanced decision-making approach should be applied to patients with AAA and cardiac disease who may require prolonged anticoagulation treatment.

Diabetes and abdominal aortic aneurysms.

Epidemiologic evidence suggests that patients with diabetes may have a lower incidence of abdominal aortic aneurysm (AAA); however, the link between diabetes and AAA development and expansion is unclear. The aim of this review is to analyze updated evidence to better understand the impact of diabetes on prevalence, incidence, clinical outcome, and expansion rate of AAA. A systematic review of literature published in the last 20 years using the PubMed and Cochrane databases was undertaken. Studies reporting appropriate data were identified and a meta-analysis performed using the generic inverse variance method. Sixty-four studies were identified. Methodological quality was "fair" in 16 and "good" in 44 studies according to a formal assessment checklist (Newcastle-Ottawa). In 17 large population prevalence studies there was a significant inverse association between diabetes and AAA: pooled odds ratio (OR) 0.80; 95% confidence intervals (CI) 0.70-0.90 (p = .0009). An inverse association was also confirmed by pooled analysis of data from smaller prevalence studies on selected populations (OR 0.59; 95% CI 0.35-0.99; p = .05), while no significant results were provided by case-control studies. A significant lower pooled incidence of new AAA in diabetics was found over six prospective studies: OR 0.54; 95% CI 0.31-0.91; p = .03. Diabetic patients showed increased operative (30-day/in-hospital) mortality after AAA repair: pooled OR 1.26; 95% CI 1.10-1.44; p = .0008. The increased operative risk was more evident in studies with 30-day assessment. In the long-term, diabetics showed lower survival rates at 2-5 years, while there was general evidence of lower growth rates of small AAA in patients with diabetes compared to non-diabetics. There is currently evidence to support an inverse relationship between diabetes and AAA development and enlargement, even though fair methodological quality or unclear risk of bias in many available studies decreases the strength of the finding. At the same time, operative and long-term survival is lower in diabetic patients, suggesting increased cardiovascular burden. The higher mortality in diabetics raises the question as to whether AAA repair should be individualized in selected diabetic populations at higher AAA rupture risk.

Current results of total endovascular repair of thoracoabdominal aortic aneurysms.

Minimally invasive surgical solutions for patients with extensive aortic disease are eagerly awaited, since open repair is often associated with high rates of morbidity and mortality. In the last decade, the development of fenestrated and branched aortic endografts has offered a therapeutic option to patients deemed unsuitable for major surgery. Preliminary studies showed promising early results, while mid- and long- term data are scarce. The aim of this paper was to review current results of total endovascular repair of thoracoabdominal aortic aneurysms (TAAA) with a single model of endograft in the published literature. A literature search was conducted, and our two-center experience with fenestrated and branched endografts in the treatment of TAAA, with the Cook Zenith endograft, is presented. Early results show perioperative mortality rates ranging from 0% to 21%, spinal cord ischemia from 0% to 33.3%. At a mean follow up ranging from 9 to 19 months, reinterventions are needed in 3.3% to 25% of the cases, with a mid term visceral branch patency of 90% to 100%. Current experiences with total endovascular TAAA repair show promising results, in selected centers with large experience in complex aortic endografting. With increasing follow- up times, need for reintervention is growing, while aneurysm-related deaths remain rare. Long-term results are still lacking, but these encouraging data and further technological developments will support wider adoption of the technique.

Effect of stentgraft model on aneurysm shrinkage in 1,450 endovascular aortic repairs.

BACKGROUND: Regression of the aneurysmal sac after endovascular repair of abdominal aortic aneurysm (AAA) is an accepted indicator of aneurysm exclusion. This study evaluated the spontaneous decrease in sac diameter over a 10-year period in patients undergoing endovascular aneurysm repair (EVAR) with different stentgrafts. METHODS: 1,450 patients (mean age 73.1 ± 7.7 years; 1,325 male) undergoing EVAR and with a minimum of 1-year computed tomography (CT) imaging were included. Different implanted stentgrafts (n = 622 [42.9%] Zenith, n = 236 [16.3%] AneuRx, n = 179 [12.3%] Talent, n = 83 [5.7%] Endurant, n = 236 [16.3%] Excluder, n = 36 [2.5%] Fortron, 53 [3.7%] Anaconda, n = 5 [0.3%] others) were employed. "Persisting shrinkage" was measured as ≥ 5 mm AAA diameter regression spontaneously persisting or increasing until the end of follow-up without reintervention. Persisting shrinkage among devices was compared with survival and Cox regression analyses. RESULTS: During a median follow-up of 45 months (interquartile range, IQR, 21-79) persisting shrinkage was detected in 768 (53%) aneurysms. Kaplan-Meier estimates of persisting shrinkage were 25.8% at 1 year, 63% at 3 years and 72.6% at 10 years. Persisting shrinkage rates were significantly higher for Zenith (p < .0001), Endurant (p = .013) and new generation Excluder (p < .0001) devices. Cox analyses confirmed that persisting shrinkage rates were independently associated with Zenith (OR 1.33; 95% CI: 1.176-1.514) and Endurant (OR 1.52; 95% CI: 1.108-2.092) stentgrafts and negatively associated with the AneuRx (OR 0.57; 95% CI: 0.477-0.688) device. Survival rates were higher in the persisting shrinkage group: 84.1% vs. 77.8% at 3 years, and 53% vs. 38.1% at 10 years (p < .0001). Freedom from AAA-related-death rate was 100% at 3 years and 99.7% at 10 years in the persisting shrinkage group. CONCLUSIONS: Aneurysm diameter shrinkage can be achieved in most current EVARs with persisting effect at 10 years from repair and indicates the benefit and safety of treatment. Last generation devices seem to be important factors in inducing aneurysm sac shrinkage with similar clinically relevant effects among single models.

Safety of carotid stenting (CAS) is based on institutional training more than individual experience in large-volume centres.

BACKGROUND: Operator training is a key factor for the safety of carotid stenting (CAS). Whether institutional practice is associated with improved individual operator outcomes is debated. OBJECTIVE: To evaluate the effect of the institutional experience on outcomes of new trainees with CAS, a retrospective analysis of a prospectively held database was performed. METHODS: The overall study period, 2004-2012, was divided into two sequential time frames: 2004-April 2006 (leaders-team phase) and May 2006-2012 (expanded team phase). In the first frame, a single leader-operators team that first approached CAS and passed the original institutional learning curve, performed all the procedures; in the following expanded-team phase, five new trainees joined. Institutional CAS training for new trainees was based on a team-working approach including selection of patients, devices and techniques and collegial meetings with critical review and discussion of all procedural steps and imaging. RESULTS: A total of 431 CAS procedures were performed in the leaders-team phase and 1026 in the sequential expanded-team phase. Periprocedural complication rates in the two time frames were similar: stroke/death (3.0% vs. 2.1%; P = 0.35), stroke (2.8% vs. 2.1%; P = 0.45) major stroke (0.9% vs. 0.6%, P = 0.49), death (0.2% vs. 0%; P = 0.29) during the leaders-team and expanded-team phase, respectively. However, rates of CAS failure requiring surgical conversions (3.7% vs. 0.8%; P < 0.0001) and mean contrast use (91.6 vs. 71.1 ml; P = 0.0001) decreased in the expanded phase. In the expanded-team frame (May 2006-2012), there was no mortality, and stroke rates were comparable between the leader and new operator teams: 2.6% vs. 1.2%; P = 0.17. CONCLUSIONS: Institutional experience, including instruction on selection of patients and materials best suited for the procedure, is a primary factor driving outcomes of CAS. An effective team-working approach can reliably improve the training of new trainees preserving CAS safety and efficacy.

No benefit from carotid intervention in fatal stroke prevention for >80-year-old patients.

BACKGROUND: Invasive management of patients ≥80 years of age with carotid stenosis may be questionable. The higher likelihood of stroke needs to be balanced with the increased perioperative risk and the reduced life expectancy of this ageing population. The purpose of this study was to evaluate the clinical relevance of carotid stenosis revascularisation in octogenarians. METHODS: All patients ≥80 years of age who received carotid revascularisation in 2001-2010 were reviewed for perioperative and 5-year outcomes. The experience was comprehensive of carotid endarterectomy (CEA) and carotid stenting (CAS) performed during the training frame when age was not a contraindication for this procedure. Mortality rates were compared to those of octogenarians of the same geographical territory according to all-cause and stroke-related mortality national statistics datasets. RESULTS: A total of 348 procedures performed in ≥80-year-old patients (272 males) were reviewed: 162 (46.6%) were by CAS and 169 (48.6%) were for symptomatic disease. Perioperative stroke/death rate was 5.5% and was non-significantly higher for symptomatic disease (7.1% vs. 3.9% asymptomatic; p = 0.24), after CAS (6.2% vs. 4.8% CEA; p = 0.64) and in females (6.6% vs. 5.1% males; p = 0.57). At median follow-up of 36.18 months, 95 deaths and 21 new ischaemic strokes (12 fatal) occurred with 5-year Kaplan-Meier freedom from stroke of 84.8% (78.7%, symptomatic vs. 90.3% asymptomatic; p = 0.003). According to national datasets, in 80-85-year-old resident population 5-year mortality was 29.9% (23.4% females, 40.6% males) and ischaemic stroke-related mortality was 14.9% (16.8% females, 13.0% males). Corresponding figures from treated population showed a 5-year mortality of 49.4%, higher in males (39.5% females, 52.5% males) and ischaemic stroke-related mortality of 20.2%, higher in females (40.0% females, 15.6% males). Comparing data from the study population with residents' figures, ischaemic stroke-related mortality hazard was significantly higher in the study females: odds ratio (OR) 3.2, 95% confidence interval (CI) 1.16-9.17; p = 0.029 (for males: OR 0.97, 95%CI 0.89-1.10; p = 0.99). CONCLUSIONS: Despite perioperative stroke/death risks being lower compared with CAS, the benefit of surgical carotid revascularisation in old patients remains controversial due to limited life expectancy and high fatality of stroke in this ageing population. Invasive treatment of carotid stenosis may not be warranted in most patients ≥80 years of age with carotid stenosis, especially when female and asymptomatic.