Lack of evidence for use of heparin-bonded grafts in access surgery: a meta-analysis.

The aim of this study was to evaluate the efficacy of heparin-bonded vascular grafts to offer improved outcomes compared with standard prosthetic grafts in access surgery. A systematic review and meta-analysis was performed and eight studies (seven observational studies and one randomized controlled trial) were included. The pooled 6-month and 1-year primary patency was not significantly different between heparin-bonded arteriovenous (AV) grafts and standard prosthetic AV grafts in seven studies reporting on 1,209 access procedures. The assisted primary patency and secondary patency at 1-year was not significantly different either. Heparin-bonded AV grafts offer no distinct advantage over standard prosthetic AV grafts and their preferential use in access surgery cannot be recommended based on the available evidence.

The Necessity for Routine Pre-operative Ultrasound Mapping Before Arteriovenous Fistula Creation: A Meta-analysis.

OBJECTIVE/BACKGROUND: Existing guidelines suggest routine use of pre-operative color Doppler ultrasound (DUS) vessel mapping before the creation of arteriovenous fistulae (AVF); however, there is controversy about its benefit over traditional clinical examination or selective ultrasound use. METHODS: This was a systematic review and meta-analysis of randomized controlled trials (RCTs) comparing routine DUS mapping before the creation of AVF with patients for whom the decision for AVF placement was based on clinical examination and selective ultrasound use. A search of MEDLINE/PubMed, SCOPUS, and the Cochrane Library was carried out in June 2014. The analyzed outcome measures were the immediate failure rate and the early/midterm adequacy of the fistula for hemodialysis. Additionally, assessment of the methodological quality of the included studies was carried out. RESULTS: Five studies (574 patients) were analyzed. A random effects model was used to pool the data. The pooled odds ratio (OR) for the immediate failure rate was 0.32 (95% confidence interval [CI] 0.17-0.60; p < .01), which was significantly in favor of the DUS mapping group. The pooled OR for the early/midterm adequacy for hemodialysis was 0.66 (95% CI 0.42-1.03; p = .06), with a trend in favor of the DUS mapping group; however, subgroup analysis revealed that routine DUS mapping was more beneficial than selective DUS (p < .05). CONCLUSION: The available evidence, based mainly on moderate quality RCTs, suggests that the pre-operative clinical examination should always be supplemented with routine DUS mapping before AVF creation. This policy avoids negative surgical explorations and significantly reduces the immediate AVF failure rate.

Computational estimation of the influence of the main body-to-iliac limb length ratio on the displacement forces acting on an aortic endograft. Theoretical application to Bolton Treovance® Abdominal Stent-Graft.

AIM: The influence of the relative iliac limb length of an endograft (EG) on the displacements forces (DF) predisposing to adverse effects are under-appreciated in the literature. Therefore, we conducted a computational study to estimate the magnitude of the DF acting over an entire reconstructed EG and its counterparts for a range of main body-to-iliac limb length (L1/L2) ratios. METHODS: A customary bifurcated 3D model was computationally created and meshed using the commercially available ANSYS ICEM (Ansys Inc., Canonsburg, PA, USA) software. Accordingly, Fluid Structure Interaction was used to estimate the DF. The total length of the EG was kept constant, while the L1/L2 ratio ranged from 0.3 to 1.5. RESULTS: The increase in L1/L2 slightly affected the DF on the EG (ranging from 3.8 to 4.1 N) and its bifurcation (4.0 to 4.6 N). However, the forces exerted at the iliac sites were strongly affected by the L1/L2 values (ranging from 0.9 to 2.2 N), showing a parabolic pattern with a minimum for 0.6 ratio. CONCLUSION: It is suggested that the hemodynamic effect of the relative limb lengths should not be considered negligible. A high main body-to-iliac limb length ratio seems to favor hemodynamically a low bifurcation but it attenuates the main body-iliac limbs modular stability. Further clinical studies should investigate the relevant value of these findings. The Bolton Treovance(®) device is presented as a representative, improved stent-graft design that takes into account these hemodynamic parameters in order to achieve a promising, improved clinical performance.

Antiplatelet treatment and prothrombotic diathesis following endovascular abdominal aortic aneurysm repair.

Prothrombotic diathesis expressed by elevated levels of coagulation-specific biomarkers has been reported in patients with abdominal aortic aneurysm (AAA) and after AAA endovascular repair (EVAR). This study investigates the effect of antiplatelet agents (APLs) on the prothrombotic diathesis in the post-EVAR period. Forty elective EVAR patients had thrombin-antithrombin complex, d-dimer, fibrinopeptide A, and high-sensitivity C-reactive protein measured before, at 24 hours, 1 month, and 6 months after EVAR. Patients receiving APLs postoperatively were compared with those not receiving APLs. All biomarkers were above the normal limits preoperatively and increased significantly 24 hours postoperatively followed by a drop at 1 and 6 months. No statistically significant changes were noted among patients receiving APLs in comparison with those not receiving APLs. The preoperative and postoperative prothrombotic diathesis of AAA following EVAR was confirmed in line with other reports. There was however no significant alteration of the examined biomarkers in patients receiving APLs.

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.

Writing a research abstract: eloquence in miniature.

Abstracts are summaries, usually of a full article or conference presentation, and may be classified into structured and unstructured ones. The former have a predefined layout necessitating the use of headings. Most journals and conferences now use the structured abstract format. Research abstracts are increasingly vital for scientific communication and are expected to continue playing a key role for the dissemination of medicine in the near future. Abstracts take time and need meticulous preparation. They must aptly summarise the content of the study or presentation and avoid vague statements and poor style. Moreover, they must comply with provided instructions. Finally, they should be pleasant to read and encourage study of the corresponding full work.

Endovascular management of peripheral arterial trauma in patients presenting in hemorrhagic shock.

AIM: This study investigated patients who sustained peripheral arterial trauma, presented with clinical signs of shock, and underwent urgent endovascular repair (endo-R). METHODS: Eighteen patients (11 men) aged 62.8 ± 17.5 y (range: 24-78 years) with severe peripheral arterial injuries or spontaneous ruptures who presented with clinical signs of shock were treated on an emergency basis at two institutions from August 2003 to August 2009. The injury mechanism and clinical presentation were assessed in all patients. The time interval from the initial event to the procedure, the time interval from hemodynamic instability to endo-R (HI-to-endo-RTI), the artery involved in the approach to the injured vessel, the method of endo-R, and the endo-R duration were recorded. Stent grafting and/or embolization of the injured vessel were performed. The outcome was assessed mainly by clinical examination and duplex scanning. The duration of follow-up ranged from 6 d to 60 mo (27.4 ± 17.8 mo, mean ± SD). RESULTS: Mechanisms of injury included 13 iatrogenic (9 catheter-related) injuries, 2 spontaneous hemorrhages, and 1 case each of gunshot wound, fall injury, and car accident. Traumatic lesions were in the external carotid (N.=1), vertebral (N.=1), subclavian (N.=3), common iliac (N.=1), external iliac (N.=5), internal iliac (N.=3), profunda femoral (N.=1), superficial femoral (N.=2), and popliteal (N.=1) arteries. Stent grafts and embolotherapy were successfully deployed in 12 and 4 patients, respectively, with complete exclusion of the bleeding site. One patient received both treatments and another patient received balloon occlusion therapy. Technical success with no procedural complications occurred in all cases. The mean event-to-procedure time interval, HI-to-endo-RTI, and operative time were 147 min, 42.2 ± 48.2 min (range: 3-180 min), and 40.0 ± 29.6 min (range: 5-110 min), respectively. Thirteen patients had an uneventful postoperative course while three patients died (mortality rate: 17%). One patient had below-knee amputation and another one suffered hemiparesis (morbidity rate: 11%). The durations of the hospital and intensive-care-unit stays were 16.6 ± 19.5 d (range: 2-62 d) and 6.4 ± 14.6 d (range: 0-60 d), respectively. The follow-up duration was 27.4 ± 17.8 mo (range: 0.2-60 mo). Freedom from early or late endo-R major events occurred in 71.4% and 65.6% of cases at 6 mo and 12 mo, respectively, and the rate of primary patency of endografts was 91.7% and 81.8%. CONCLUSION: Endo-R of traumatic non-aortic arterial injuries or spontaneous ruptures might be considered as a treatment option-in preference to open repair-even in emergency settings such as in shock patients. However, the safety of endovascular treatment in unstable trauma patients must be proved after comparison with open surgical treatment.

Circulating matrix metalloproteinases and their inhibitors in inguinal hernia and abdominal aortic aneurysm.

AIM: There is evidence supporting the role of matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) in aortic and abdominal wall connective tissue degeneration, resulting in aneurysm and hernia formation. Furthermore, clinical association studies have demonstrated increased prevalence of abdominal wall hernias in patients with aortic aneurysms. Our objective was to estimate the levels of MMPs and TIMPs in the blood of patients with aortic aneurysm and inguinal hernia, in order to investigate whether there is potential pathogenic linkage of impaired collagen metabolism. METHODS: Plasma concentrations of MMP-9, MMP-2, TIMP-1 and TIMP-2 were quantified using ELISA in 33 male patients with abdominal aortic aneurysm and 91 male patients with inguinal hernia. They were consecutive patients undergoing repair during the study period. The same substances were measured in 35 healthy male controls. RESULTS: MMP-9 and MMP-2 concentrations were lower in the plasma of patients with inguinal hernia and abdominal aortic aneurysm than controls, with hernia patients having the lowest circulating levels. The levels of TIMP-2 were significantly elevated in patients with inguinal hernia and significantly reduced in patients with aortic aneurysm, whereas opposite correlations were found for circulating TIMP-1. CONCLUSION: Different patterns of circulating MMP and TIMP levels were found in patients with aneurysm and hernia compared with controls. Underlying pathogenic processes implicating MMPs and TIMPs in connective tissue metabolism are expressed by differing plasma levels in the two disease states. Further research including combined plasma and tissue analyses is required to further investigate potential common pathogenesis of these diseases.

Delivering a powerful oral presentation: all the world's a stage.

Oral presentations are, to a great extent, a matter of talent, but they can be practised and improved. There are three kinds of presentations: the short talk (5-10 minutes), the intermediate talk (15 minutes) and the long talk (approximately 45 minutes). Whatever the kind of the presentation, careful preparation is mandatory. The speaker needs to know how long the presentation is expected to be, who the audience is and what main messages should be conveyed. Power point and other visual aids may be appropriately used to facilitate communication. The information presented by these aids should be simple, concrete and intelligible, and the presenter should refrain from reading out the slides word for word. During the presentation, several pitfalls should be avoided: wrong type of presentation, exceeding the allocated time, poor structure, inadequate use of power point and/or other visual aids, poor control of language, poor control of voice, poor appearance on the podium, and poor control of nerves. Ideally, the successful oral presentation is a performance. Thus, the speaker may make the most of appearance, voice, eye contact and movement, in order to increase eloquence.

Letters to the editor: definitely not children of a lesser god.

Letters to the editor are brief texts that are published in a special section of medical journals. There are two types of letters to the editor: the observation and the comment. The former presents original work, while the latter constitutes criticism on work already published in the same journal. Although short, letters to the editor require as much effort and discipline in writing as, indeed, any other manuscript. Clarity and brevity should be their principal values. It is also important to comply with the journals' instructions for correspondence. Thus, eloquent letters to the editor may promote knowledge and enable fruitful exchange of ideas.

Lower-extremity arteriovenous access for haemodialysis: a systematic review.

BACKGROUND: The lower extremity is increasingly used as an access site in end-stage renal disease patients. However, reports present conflicting results, creating confusion regarding the feasibility and outcomes. Our objective is to review the available literature and analyse the patency rates and complications of various types of lower-extremity arteriovenous access. METHODS: An Internet-based literature search was performed using MEDLINE to identify all published reports on lower-extremity vascular access. The analysis involved studies comprising at least 10 arteriovenous accesses with both inflow and outflow vessels in the lower extremity, and reporting on patency rates and access-related complications. The weighted mean patency rates were calculated, and the chi-square (chi(2)) test was used to evaluate the differences in the complication rates in the subgroups of patients identified. RESULTS: Three main types of lower-extremity vascular access were identified: the upper thigh prosthetic, the mid-thigh prosthetic and the femoral vein transposition arteriovenous access. There are limited data on saphenous vein loop grafts, which report poor results. The weighted mean primary patency rates at 12 months were 48%, 43% and 83%, respectively. The weighted mean secondary patency rates at 12 months were 69%, 67% and 93%, respectively. Access loss as a result of infection was more common in upper thigh and mid-thigh grafts than femoral vein transposition arteriovenous access (18.40%, 18.33% vs. 1.61%; P<0.05). Ischaemic complications rates were higher in autologous than prosthetic arteriovenous access (20.97% vs. 7.18%, P<0.05). CONCLUSIONS: Lower-extremity vascular access has acceptable results in terms of patency, with femoral vein transposition having better patency rates than femoral grafts. Autologous access is associated with less infective complications, however, at the expense of increased ischaemic complications rates. Further research with randomised trials is required to assess the outcomes of lower-extremity vascular access.

Arterial spasm mimicking superficial femoral artery trauma. Case report.

The existence of traumatic arterial spasm in large arteries is questionable in current literature. We report a case of a 19-year old man with comminuted unstable femur fracture who presented with an ischemic foot. Localized arterial spasm was revealed in the middle portion of the superficial femoral artery triggered by the external pressure of a spicular bone segment was revealed by arteriography. Complete resolution of ischemic symptoms followed fracture reduction. Traumatic arterial spasm although rare does exist.

Risk factors for ipsilateral reamputation in patients with diabetic foot lesions.

This study aimed to examine the rates and risk factors for ipsilateral re-amputation in 121 patients with diabetic foot and prior amputation. Twenty-six (21.5%) patients required re-amputation during a mean follow-up of 18 months. Most re-amputations were performed within the first 6 months of the initial amputation. Re-amputation was more common among patients in whom the initial amputation had only affected one or two toes. Age (hazard ratio: 1.06) and heel lesions (hazard ratio: 2.69) were significantly associated with re-amputation. There is a high risk of re-amputation in the diabetic foot, especially within the first 6 months of the initial amputation, mainly due to poor selection of the original amputation level in an effort to save a greater part of the lower extremity. Patients 70 years and those with heel lesions are at greatest risk of re-amputation.

Transposed brachial-basilic arteriovenous fistulas versus prosthetic upper limb grafts: a meta-analysis.

BACKGROUND: Controversy exists regarding the best type of arteriovenous (AV) fistula to be formed in secondary and tertiary access procedures when primary fistulas have failed. This meta-analysis aimed to compare transposed brachial-basilic AV fistulas (BBAVFs) with upper limb AV prosthetic grafts. METHODS: A literature search of the MEDLINE and SCOPUS databases was performed to identify comparative studies reporting outcomes for both BBAVFs with upper limb AV prosthetic grafts. Meta-analysis techniques were applied to identify differences in outcomes between the two groups regarding primary and secondary 1-year failure rates. RESULTS: Eleven relevant studies, involving 1509 patients, met the inclusion criteria and were incorporated in the final analysis; however, only one was randomised controlled trial. The pooled odds' ratio (OR) estimate for the primary and secondary failure rates at 1 year was 0.67 (CI 0.41-1.09) and 0.88 (CI 0.69-1.12), respectively, showing no difference in the outcome between the two groups. The re-intervention rate was higher for prosthetic grafts (0.54 per BBAVF versus 1.32 per graft). In a small subgroup of two studies comparing BBAVFs with forearm grafts the pooled estimate for 1-year primary failure rate was in favour of the BBAVF group (OR 0.3, CI 0.15-0.58, p=0.0004) suggesting that forearm grafts were inferior having a 3-fold risk of failure at 1 year. CONCLUSION: This analysis supports the use of BBAVF early in difficult access cases prior to the use of prosthetic grafts. However, the latter conclusion is debatable due to heterogeneity, small size and non-randomised design of the included studies.

Writing a case report: polishing a gem?

Case reports describe patient cases which are of particular interest due to their novelty and their potential message for clinical practice. While there are several types of case reports, originality and clinical implications constitute the main virtues by which case reports are judged. Defining the educational message and choosing the right audience are vital steps in the process of writing. Generally, a case report is structured, its main components being the abstract, the introduction, the case description and the discussion. Guidelines and tips for writing case reports are not enough for making a successful author, but they help, especially less experienced doctors, to exercise and improve their writing. If properly prepared, case reports can still communicate new observations in an interesting and pleasant way, thereby enriching our knowledge, even in the era of evidence-based medicine.