Ali Bakran

Endotension after endovascular aneurysm repair: definition, classification, and strategies for surveillance and intervention.

In the ongoing evolution of a categorization system for endoleak, the authors propose the term endotension to define persistent or recurrent pressurization of the aortic aneurysm sac after endovascular repair. Endotension is evidence that the aneurysm remains at risk of rupture and should, therefore, be considered an indication for secondary intervention. Management strategies and a grading system for endotension are offered.

Longitudinal aneurysm shrinkage following endovascular aortic aneurysm repair: a source of intermediate and late complications.

PURPOSE To report the incidence of delayed complications following endovascular abdominal aortic aneurysm (AAA) repair and the relationship of these sequelae to morphological changes in the sac and endograft. METHODS Twenty-six AAA patients treated with Vanguard endografts had completed > or = 1-year follow-up. Postoperative angiograms and spiral computed tomographic (CT) scans with 3-dimensional reconstruction were compared to the 1-year images to determine morphological changes in the aneurysm sac and the endograft. These changes were then related to complications occurring between 1 and 12 months postoperatively in the study group. RESULTS Comparison of angiograms uncovered endograft buckling in 18 (69%) patients and acutely angled or kinked endografts in 10 (38%). Measurements from the CT scans found that undistorted endografts had a mean change in sac length of +6.6 mm. Mean sac length change in buckled endografts was -3.1 mm, while kinked endografts displayed a mean change of -6.2 mm (p < 0.002, Students t-test). Five (19%) patients, all with distorted endografts, demonstrated late (1 to 12 months) complications (4 endoleaks and 1 graft limb thrombosis) owing to component separation, distal stent migration, and acute angulation. No movement in the proximal stent was observed. Elongation of the endograft (flow line measurement) was observed in one tube graft only. CONCLUSIONS In this study, longitudinal shrinkage of the sac following endovascular aortic aneurysm repair led to buckling or kinking of the endograft within 1 year in 69% of patients. This appears to be an important source of delayed complications.

Use of contrast-enhanced ultrasound in follow-up after endovascular aortic aneurysm repair

PURPOSE To investigate the use of contrast-enhanced ultrasound in the detection of endoleak after endovascular repair of abdominal aortic aneurysm. MATERIALS AND METHODS Eighteen patients underwent follow-up on 20 occasions after endovascular aortic aneurysm repair by arterial-phase contrast-enhanced spiral computed tomography (CT). All patients had unenhanced color Doppler ultrasound and Levovist-enhanced ultrasound on the same day. The ultrasound examinations were reported in a manner that was blind to the CT results. CT was regarded as the gold standard for the purposes of the study. RESULTS There were three endoleaks shown by CT. Unenhanced ultrasound detected only one endoleak (sensitivity, 33%). Levovist-enhanced ultrasound detected all three endoleaks (sensitivity, 100%). Levovist-enhanced ultrasound indicated an additional six endoleaks that were not confirmed by CT (specificity, 67%; positive predictive value, 33%). In one of these six cases, the aneurysm increased in size, which indicates a likelihood of endoleak. Two of the remaining false-positive results occurred in patients known to have a distal implantation leak at completion angiography. CONCLUSION In this small group of patients, contrast-enhanced ultrasound appears to be a reliable screening test for endoleak. The false-positive results with enhanced ultrasound may be due to the failure of CT to detect slow flow collateral pathways. Although the number of patients in this study is small, enhanced ultrasound may be more reliable than CT in detecting endoleak.

Flow patterns in the radiocephalic arteriovenous fistula: an in vitro study.

A significant number of late failures of arteriovenous fistulae for haemodialysis access are related to the progression of intimal hyperplasia. Although the aetiology of this process is still unknown, the geometry of the fistula and the local haemodynamics are thought to be contributory factors. An in-vitro study was carried out to investigate the local haemodynamics in a model of a Cimino-Brescia arteriovenous (AV) fistula with a 30 degrees anastomotic angle and vein-to-artery diameter ratio of 1.6. Flow patterns were obtained by planar illumination of micro-particles suspended in the fluid. Steady and pulsatile flow studies were performed over a range of flow conditions corresponding to those recorded in patients. Quantitative measurements of wall shear stress and turbulence were made using laser Doppler anemometry. The flow structures in pulsatile flow were similar to those seen in steady flow with no significant qualitative changes over the cardiac cycle. This was probably the result of the low pulsatility index of the flow waveform in AV fistulae. Turbulence was the dominant feature in the vein, with relative turbulence intensity > 0.5 within 10 mm of the suture line decreasing to a relatively constant value of about 0.10-0.15 between 40 and 70 mm from the suture line. Peak and mean Reynolds shear stress of 15 and 20 N/m2, respectively, were recorded at the suture line. On the floor of the artery, peak values of temporal mean and oscillating wall shear stress of 9.22 and 29.8 N/m2, respectively. In the vein, both mean and oscillating wall shear stress decreased with distance from the anastomosis.

Effect of conversion from mycophenolate mofetil to enteric‐coated mycophenolate sodium on maximum tolerated dose and gastrointestinal symptoms following kidney transplantation

Despite the potential tolerability advantage of enteric‐coated mycophenolate sodium (EC‐MPS), no prospective, randomized trial has evaluated whether conversion from mycophenolate mofetil (MMF) to EC‐MPS permits mycophenolic acid dose to be increased or gastrointestinal side‐effects to be ameliorated. In a randomized, multicenter, open‐label trial, kidney transplant recipients experiencing gastrointestinal side‐effects either remained on MMF or switched to an equimolar dose of EC‐MPS, adjusted 2 weeks subsequently to target the highest tolerated dose up to 1440 mg/day (EC‐MPS) or 2000 mg/day (MMF). Patients were followed up to 12 weeks postrandomization. One hundred and thirty‐four patients were randomized. The primary efficacy endpoint, the proportion of patients receiving a higher mycophenolic acid (MPA) dose at week 12 than at randomization, was significantly greater in the EC‐MPS arm (32/68, 47.1%) than the MMF arm (10/61, 16.4%; P < 0.001). At the final visit, 50.0% (34/68) of EC‐MPS patients were receiving the maximum recommended dose versus 26.2% (16/61) of MMF patients (P = 0.007). Kidney transplant patients receiving reduced‐dose MMF because of gastrointestinal side‐effects can tolerate a significant increase in MPA dose after conversion to EC‐MPS. Patient‐reported gastrointestinal outcomes with higher doses of EC‐MPS remained at least as good as in MMF‐treated controls.

ePTFE grafts for femoro-crural bypass:improved results with combined adjuvant venous cuff and arteriovenous fistula?

Patency rates for long prosthetic bypass grafts with standard anastomoses to single tibial or peroneal arteries are very poor. Adjuvant techniques employed with the aim of improving patency rates include arteriovenous fistula (AVF) at the distal anastomosis to accelerate blood flow above thrombotic threshold velocity (TTV) and a venous cuff (VC) or patch which may reduce or modify anastomotic myointimal hyperplasia within the recipient artery. In a consecutive series of 43 femoro-crural bypasses with ePTFE grafts, adjuvant AVF and VC procedures have been applied in combination. The results are compared with those of an antecedent series of 76 similar grafts with AVF alone and a contemporaneous series of 179 autologous vein grafts. All operations were undertaken for critical limb ischaemia with anastomosis to a single calf or pedal artery. The three groups were well matched for age, sex, diabetes, smoking history, previous surgery and the proportion with rest pain and tissue necrosis. The cumulative patency rate at 2 years for ePTFE grafts with combined AVF and VC was 62% compared to 28% for those with AVF alone and 68% for autologous vein grafts. The patency rate for prosthetic grafts with AVF and VC was significantly higher than AVF alone (p < 0.01) and did not differ significantly from vein grafts. Cumulative limb salvage rates for ePTFE grafts with AVF and VC were 68% at 1 year and 55% at 2 years compared to 38 and 35% for AVF alone and 78 and 69% for vein grafts.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical outcome of cadaveric renal allografts contaminated before transplantation

This analysis was performed to define the incidence of pretransplant microbial contamination of donor kidneys, and to assess the resultant morbidity including infections requiring therapy, and graft loss. Case records of all 638 renal allograft recipients patients transplanted in our centre during the period June 1990 to October 2000 were studied. All the recipients were given a single dose of intravenous antibiotics at the time of induction of anaesthesia. A total of 775 microbiology reports on perfusion fluid, kidney swabs and ureteric tissue were retrieved. Fifty‐eight of 638 (9.1%) patients were transplanted with a graft that showed preoperative contamination. 18 of these 58 patients (31%) subsequently required antibiotic treatment. Thirty of 32 patients who received kidney contaminated with skin flora had a benign course (i.e. no unexplained, no positive blood cultures or graft infection). By contrast, seven of nine recipients with grafts whose perfusion fluid yielded lactose fermenting coliforms (LFCs) required antibiotics and three of nine of them suffered graft loss as a result. Two of these patients had bacteraemia caused by LFC, and one died. Three of five patients with positive cultures due to yeast required treatment with antifungals. None of the four patients who had graft contaminated by Staphylococcus aureus became infected. One‐year 49/58 (85%) of these patients survived with functioning graft. Overall 1‐year patient survival was 53/55 (92%). These data suggest that contamination of renal allografts by LFCs or yeasts need to be treated preemptively before the onset of clinical manifestations. By contrast, contamination with skin contaminants does not pose a risk to the graft.

Intra-arterial Injection of Temazepam in Drug Abusers

The effects of intra-arterial injection of Temazepam are described in 11 drug abusers admitted over a 6 month period. All patients suffered severe ischaemia, and injection into the radial artery invariably resulted in tissue loss leading to amputation. The pathogenesis and options for treatment are discussed.

Morphology, calcium signaling and mechanical activity in human ureter

PURPOSE We determined the mechanisms of calcium signaling in the human ureter, and the relationship to peristaltic contractions and bundular structure in living tissue, thereby advancing the understanding of ureteral function in health and obstruction and reflux. MATERIALS AND METHODS Confocal imaging of 31 ureters was performed and simultaneous force and calcium measurements were made. Immunohistochemistry and Western blotting were also performed. RESULTS Confocal imaging showed a 3-dimensional network of smooth muscle bundles with no defined longitudinal or circular layers. Fast propagating Ca waves spread throughout the bundles, were closely associated with contraction and depended on L-type Ca channel entry. Immunohistochemistry and Western blotting demonstrated L-type Ca channels, Ca dependent K channels, sarcoplasmic reticulum Ca-adenosine triphosphatase isoforms 2 and 3, inositol triphosphate, and ryanodine receptors. Modulation of Ca and K channel activity was a potent mechanism for affecting Ca and force, whereas manipulation of the sarcoplasmic reticulum had little effect. CONCLUSIONS To our knowledge this study represents the first measurements of Ca signals in the human ureter obtained during phasic contractions and in response to agonists. Results show that it is controlled by fast propagating Ca waves, which spread rapidly between the muscle bundles, producing regular contractions, and drugs that interfere with excitability or Ca entry through L-type Ca channels have profound effects on Ca signaling and contractility. These data are discussed in relation to the treatment of patients with suspected ureteral dysfunction using Ca entry blockers.

Outflow distribution at the distal anastomosis of infrainguinal bypass grafts

Outflow distribution at the distal anastomosis of infrainguinal bypass grafts remains unquantified in vivo, but is likely to influence flow patterns and haemodynamics, thereby impacting upon graft patency. This study measured the ratio of distal to proximal outflow in 30 patients undergoing infrainguinal bypass for lower limb ischaemia, using a flow probe and a transit-time ultrasonic flow meter. The mean outflow distribution was approximately 75% distal to 25% proximal, with above knee anastomoses having a greater proportion of distal flow (84%) compared to below knee grafts (73%). These in vivo flow characteristics differ significantly from those used in theoretical models studying flow phenomena (50:50 and/or 100:0), and should be incorporated into future research.