In vitro and In vivo assessment of a novel organ perfusion stent for successful flow separation in donation after cardiac death.

Shortage of healthy donors' organs has appeared as one of the main challenges for organ transplantation. This study focuses on the novel endovascular device development to increase the number of available organs from cardiac death donors. The primary objective of this study is the design validation of a newly developed stent graft for the abdominal organ perfusion with cardiac blood flow isolation. In this paper, the effectiveness of the device design has been validated via the assessment of the device performance both in vitro and in vivo. The radial force of stent structure was first numerically analyzed using finite element method, then was quantified experimentally. The blood perfusion parameters were investigated to demonstrate their effect on the blood delivered to the abdominal organs, maintaining the organs healthy for donation. In vitro flow leakage was measured using a 3-D printing-based silicone aortic model to evaluate the isolation between cardiac flow and perfusion flow with minimum values. Following the design validation process, a functional prototype stent graft has been successfully fabricated using optimized laser welding conditions and subsequent joining processes. In vivo porcine study results have demonstrated smooth delivery and successful placement of the device showing complete cardiac flow separation isolating abdominal regions only with the oxygenated blood flow.

Female Gender is a Predictor of Lower Iliac Vein Stenting Patency Rates.

BACKGROUND: Iliac venous stenting (IVS) for thrombotic and nonthrombotic venous disease is increasingly used as evidence of the safety, efficacy and durability of these interventions increases. Female gender has been implicated as a predictor of failure in arterial endovascular interventions. We hypothesize that female gender could be predictive of patency rates of iliac vein stenting. METHODS: Consecutive patients who underwent IVS for thrombotic or nonthrombotic venous disease at our institution from 2007 until 2019 were identified and divided into groups based on gender. Operative notes, venograms, and the electronic health record were then queried to obtain operative details, co-morbid conditions, postoperative outcomes and stent patency. Study outcome was long term patency rate. The data was analyzed using chi-square, logistic regression, and Kaplan-Meier analysis as appropriate. RESULTS: A total of 200 consecutive patients (231 limbs) were identified in our retrospective analysis, with a mean age of 48.8 ± 17.3, and BMI of 31.6 ± 8.6. Of those, 119 (59.5%) patients, (131 [56.8%] limbs) were female. Comparisons between the gender groups revealed no difference in age, BMI, or preoperative comorbidities. There was no difference in type of venous disease between male (85% thrombotic, 15% nonthrombotic) and female (84% thrombotic, 16% nonthrombotic), P= 0.830. The male cohort was more likely to present with leg ulceration (17% vs. 4.6%, P = 0.002), and the female cohort was more likely to present with leg edema (98.5% vs. 93.0%, P= 0.03). The male cohort had a higher rate of caval (48% vs. 33.6%, P= 0.027) and infrainguinal stent extension. (11% vs. 6.9%, P= 0.02). Females had a higher rate of left sided stenting (80.9% vs. 66/0%, P= 0.010). There was no difference in the median stent diameter used between the cohorts. Primary patency at 5 years was significantly higher for the male cohort (94.1% vs. 74.4%, P= 0.01) On adjusted multivariable cox regression female gender was a predictor of loss of primary patency within 5 years (HR, 4.04; P= 0.007). CONCLUSIONS: In this single center retrospective analysis of IVS, male patients were found to have better primary stent patency compared to female.

Letters of recommendation: Nuanced bias or useful affirmation?

Narrative letters of recommendation (NLORs) have become key elements of the application process for residency and fellowship. The potential to inadvertently admit bias into these subjective narratives has become an area of research focus across many disciplines. In the present review, we have highlighted the current data regarding bias in NLORs. We also believe that one of the most effective methods to eliminate bias from written recommendations is to first understand that it exists. Thus, the objective measures that have been taken to identify bias in NLORs are important steps in the right direction. We have presented and reflected on the accrued data on bias in NLORs pertaining to surgical training.

Assessment of mechanical and biocompatible performance of ultra-large nitinol endovascular devices fabricated via a low-energy laser joining process.

Nitinol is an excellent candidate material for developing various self-expanding endovascular devices due to its unique properties such as superelasticity, biocompatibility and shape memory effect. A low-energy laser joining technique suggests a high potential to create various large diameter Nitinol endovascular devices that contain complex geometries. The primary purpose of the study is to investigate the effects of laser joining process parameters with regard to the mechanical and biocompatible performance of Nitinol stents. Both the chemical composition and the microstructure of the laser-welded joints were evaluated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). In vitro study results on cytotoxicity demonstrated that the joining condition of 8 Hz frequency and 1 kW laser power showed the highest degree of endothelial cell viability after thermal annealing in 500°C for 30 min. Also, in vitro study results showed the highest oxygen content at 0.9 kW laser power, 8 Hz frequency, and 0.3 mm spot size after the thermal annealing. Mechanical performance test results showed that the optimal condition for the highest disconnecting force was found at 1 Hz frequency and 1 kW power with 0.6 mm spot size. Two new endovascular devices have been fabricated using the optimized laser joining parameters, which have demonstrated successful device delivery and retrieval, as well as acute biocompatibility.

Comprehensive assessment of mechanical behavior of an extremely long stent graft to control hemorrhage in torso.

Traumatic vascular injuries, resulting from either civilian accidents or wounded soldiers, require new endovascular devices (i.e., stent graft) to rapidly control the excessive internal hemorrhage in torso region. Current stent designs are limited by their permanent nature, which is note well suited for emergent placement. A retrievable stent graft could regulate the internal bleeding temporarily, as fast as possible with the most feasible performance, until the patients arrive the hospital to receive the proper treatment. The novel endovascular device of this study is designed according to the anatomy of a porcine model with plans to transition to a human model in the future. The stent graft is manufactured using a substantially long nitinol backbone and covered selectively based on anatomic measurements, with highly stretchable expanded-polytetrafluoroethylene (ePTFE). In this study, our group comprehensively explored designing and manufacturing methods, and their impact on the stent graft performance. Geometric parameters and heat treatment conditions were investigated to show their effect on the radial force of the metallic backbone. As a retrievable device, the resistance force for retrieval as well as deployment were measured, and analyzed to be manipulated through ePTFE covering configurations. In vitro measurements for bleeding were measured using swine aorta to show the functionality of the stent graft under the simulated pulsatile flow circulation. Finally, the stent graft showed substantial effectiveness for hemorrhage control in vivo, using swine model. The new design and fabrication methods enable rapid hemorrhage control that can be removed at the time of a dedicated surgical repair.

Single- versus multiple-stage catheter-directed thrombolysis for acute iliofemoral deep venous thrombosis does not have an impact on iliac vein stent length or patency rates.

BACKGROUND: Incomplete venous thrombolysis and residual nonstented iliac vein disease are known predictors of recurrent deep venous thrombosis (DVT). Controversy exists as to whether the number of thrombolysis sessions affects total stent treatment length or stent patency. The goal of this study was to evaluate the outcomes of patients who underwent single vs multiple catheter-directed lysis sessions with regard to stent extent and patency. METHODS: Consecutive patients who underwent thrombolysis and stenting for acute iliofemoral DVT between 2007 and 2018 were identified and divided into two groups on the basis of the number of treatments performed (one vs multiple sessions). Operative notes and venograms were reviewed to determine the number of lytic sessions performed and stent information, including size, location, total number, and length treated. End points included total stent length, 30-day and long-term patency, and post-thrombotic syndrome (Villalta score ≥5). The χ2 comparisons, logistic regression, and survival analysis were used to determine outcomes. RESULTS: There were 79 patients who underwent lysis and stenting (6 bilateral interventions; mean age, 45.9 ± 17 years; 48 female). Ten patients (12 limbs) underwent single-stage treatment with pharmacomechanical thrombolysis, and the remaining 69 (73 limbs) had two to four operating room sessions combining pharmacomechanical and catheter-directed thrombolysis. Patients who underwent a single-stage procedure were older and more likely to have a malignant disease. These patients received less tissue plasminogen activator compared with the multiple-stage group (17.2 ± 2.2 mg vs 27.6 ± 11.6 mg; P = .008). Average stent length was 8.8 ± 5.2 cm for the single-stage group vs 9.2 ± 4.6 cm for the multiple-stage group (P = .764). Patients who underwent a single-stage procedure had no difference in average length of stay from that of patients who underwent multiple sessions (8.5 days vs 5.9 days; P = .269). The overall 30-day rethrombosis rate was 7.3%. Two-year patency was 72.2% and 74.7% for the single and multiple stages, respectively (P = .909). The major predictors for loss of primary patency were previous DVT (hazard ratio [HR], 5.99; P = .020) and incomplete lysis (HR, 5.39; P = .014) but not number of procedures (HR, 0.957; P = .966). The overall post-thrombotic syndrome rate was 28.4% at 5 years and was also not associated with the number of treatment sessions. CONCLUSIONS: Single- vs multiple-stage thrombolysis for DVT is not associated with a difference in extent of stent coverage. Patency rates remain high for iliac stenting irrespective of the number of lytic sessions, provided lysis is complete and the diseased segments are appropriately stented.

Survival and long-term cardiovascular outcomes after carotid endarterectomy in patients with chronic renal insufficiency.

BACKGROUND: Multiple studies have evaluated the perioperative outcomes of patients with chronic renal insufficiency (CRI) undergoing carotid endarterectomy (CEA), generally indicating worse survival and cardiovascular (CV) outcomes, although not consistently and with a paucity of long-term data. The present study addresses the perioperative and long-term impact of CRI on CV events and survival after CEA. METHODS: A cohort of consecutive patients treated with CEA between January 1, 2000, and December 31, 2008, was analyzed based on medical records and Social Security Death Index. Estimated glomerular filtration rate (GFR) was assessed at baseline. Renal function was used to divide patients into 3 groups: normal (GFR ≥ 60 mL/min/1.73 m(2)), moderate CRI (GFR, 30-59), and severe CRI (GFR <30). The end points were major coronary events, major cerebrovascular events (any stroke), noncardiac vascular interventions (aortic disease, carotid disease, and critical limb ischemia), and mortality. Subgroup analysis based on the presence of preoperative neurologic symptoms was also performed. Survival analysis and Cox regression models were used to assess the effect of baseline predictors. RESULTS: A total of 1,342 CEAs (mean age, 71.2 ± 9.2 years; 55.6% male; 35.3% symptomatic) were performed during the study period with a mean clinical follow-up of 57 months (median, 55; range, 0-155 months). Eight hundred sixty-eight (65%) patients had normal renal function, 414 (31%) had moderate CRI, and 60 (4%) had severe CRI (24 on dialysis). The combined 30-day stroke/death rates for the symptomatic and asymptomatic groups were 3.2% and 1.4% (normal renal function), 5.7% and 2.6% (moderate CRI), and 14.3% and 10.3% (severe CRI), respectively, with the differences being significant only for the severe-CRI group. At 5 years, the severe-CRI group experienced significantly more coronary events (36.9% vs. 16.3%, P < 0.001), more cerebrovascular events (21.6% vs. 6.3%, P < 0.001), and deaths (70.0% vs. 20.3%, P < 0.001), whereas the moderate-CRI group had no significantly different outcomes compared with the normal group, except for mortality (29.8% vs. 20.3%, P < 0.001). After adjusting for all risk factors, severe CRI remained predictive of coronary events (hazard ratio [HR], 2.21; 95% confidence interval [CI], 1.25-3.90; P = 0.007), cerebrovascular events (HR, 3.11; 95% CI, 1.44-6.74; P = 0.004), and mortality (HR, 4.36; 95% CI, 3.00-6.34; P < 0.001). Symptomatology at baseline was predictive of 5-year mortality (HR, 1.43; 95% CI, 1.14-1.81; P = 0.002). The need for noncardiac vascular interventions was equally distributed among all the groups. CONCLUSIONS: Severe but not moderate CRI is associated with poor perioperative outcomes and is an independent predictor of CV events and death at 5 years after CEA. The decision to perform CEA in symptomatic and asymptomatic patients with severe CRI should be individualized given the poor reported outcomes.