Smaller Sheath Research Articles

High‐voltage antenna‐plasma interaction in whistler wave transmission: Plasma sheath effects

We study the plasma sheath surrounding an antenna that transmits whistler mode waves in the inner magnetosphere in order to investigate the feasibility of conducting controlled experiments on the role of wave‐particle interactions in the pitch angle diffusion of relativistic radiation belt electrons. We propose a model for an electrically short antenna‐sheath‐plasma system with transmission frequencies below the electron characteristic frequencies and much higher than the ion characteristic frequencies. The ion current is neglected. We analytically solve a time‐dependent one‐dimensional situation by neglecting the effects of the wave's magnetic field. In our model, the antenna is charged to a large negative potential during a steady transmission. Positive charge occurs in the sheath and the sheath is free of electrons and conduction current. The net charge on the antenna and in the sheath is zero. The volume, or the radius in a cylindrical case, of the sheath varies in response to the charge/voltage variation on the antenna. The oscillating radius of the sheath translates to a current in the plasma, which radiates waves into the plasma. A whistler wave transmission experiment conducted by the RPI‐IMAGE has shown that the model may describe the most important physical processes occurring in the system. The system response is predominately reactive, showing no evidence for significant sheath current or sheath resistance. The negligibly small sheath conduction electron current can be understood if the antenna is charged to a substantial negative potential, as described by the model. Quantitatively, the model may underestimate the sheath capacitance by about 20%.

Development of a reexpandable covered stent for children

The use of covered stents in children is limited by the need for a large long sheath for delivery and the impossibility of redilation once implanted. The authors developed a reexpandable covered stent implantable in children through a small sheath and evaluated its clinical feasibility in mini piglets. An original Palmaz stent was covered with a polyurethane membrane that could be stretched up to 700%. Under general anesthesia, the authors implanted the covered stents in six mini piglets using a long sheath with a diameter approximately 1 French larger than the recommended size required to deliver an uncovered Palmaz stent. The implantation technique was similar to conventional stent implantation. In six piglets, the stent could be redilated from 7.5 to 8.7 mm 28-70 days after implantation. Macroscopic and microscopic examination showed intimal coverage of the coating with minimal inflammatory reaction around the stent. Our newly designed reexpandable stent covered with a polyurethane membrane is promising for use in children.

Clinical Application of an Original Flexible MK Stent-Graft for Nonruptured Thoracic Aortic Aneurysms: Early Experience

: To obtain early MK stent-grafting results for nonruptured thoracic aortic aneurysms and thoracoabdominal aortic aneurysms. : The authors analyzed 47 patients who underwent treatment using MK stent-grafting. All patients (40 men and 7 women; mean age, 70.8 years) underwent elective procedures. Straight, curved, or tapered MK stents were constructed from a nitinol wire and covered with seamless, cylindrical woven polyester fabric grafts. The mean stent-graft diameter was 24 to 48 mm. In cases where the aneurysm had a short proximal neck (under 15 mm), supraaortic arch artery bypass surgery was planned to lengthen the neck. : Simple stent-grafting without bypass was performed in 26 patients, whereas stent-grafting with supraaortic arch artery bypass was performed in 21 patients. An 18 or 20 F sheath was used as the delivery system in 46 patients (96%). In all 47 patients, the stent-grafts were successfully deployed. Two patients died while in hospital, and another 2 patients suffered a stroke. No other perioperative complications were observed. Postoperative computed tomography after 3 months showed complete thrombus formation in 42 patients (93.3%; 42/45 patients). : Forty-seven patients with thoracic aortic aneurysm were treated with our original flexible MK stent-graft system. Using a small sheath system, straight or curved M-K stent-grafts could be deployed to adequately fit to the aorta as planned. Furthermore, simultaneous bypass surgery widened the application of stent-grafting. However, careful long-term observation is necessary, and further studies are needed to assess such stent-grafting with bypass surgery.

Techniques for large sheath insertion during endovascular thoracic aortic aneurysm repair

Despite improvements in operative technique and perioperative management, conventional open repair of descending thoracic aortic aneurysms (DTAs) continues to be associated with significant morbidity and a perioperative mortality between 4.8% and 20%, which may be even more pronounced in the acute setting. Since the first description of the endovascular repair of a thoracic aortic aneurysm by Dake et al, several studies have shown the safety of this approach, as well as possible decreases in perioperative mortality and complications, most notably paraplegia. Because of the less invasive nature and likely improved perioperative outcomes of endovascular repair of DTA, this is rapidly becoming the favored approach for management in these patients. Many patients, however, continue to be ineligible because of suboptimal vascular access, aortic arch angulation, and landing zone inadequacies. Although industry has been working to solve the last two issues, vascular access continues to be of major concern because delivery systems remain excessively large. In the United States, the currently available endografts for thoracic aorta aneurysms require delivery sheaths ranging from 20F to 25F, depending on the size of the graft and the manufacturer (Table). Despite these challenges, with the recent approval by the US Food and Drug Administration of the Gore Thoracic Aortic Graft endoprosthesis (W.L. Gore and Associates, Inc, Flagstaff, Ariz) and the ongoing evaluation of the Talent (Medtronic, Santa Rosa, Calif) and Zenith TX1 and TX2 (Cook Inc, Bloomington, Ind) endografts, it is clear that this technology is moving forward. With more widespread use and continued innovation, industry should be able to overcome the difficulties currently encountered with vascular access for the introduction of thoracic aortic endografts. Until that time, however, one should be knowledgeable of and comfortable with the implementation of several adjunctive maneuvers that may allow graft placement in otherwise ineligible patients. Furthermore, a thorough knowl-

Low-profile Stent Placement with the Monorail Technique for Treatment of Renal Artery Stenosis: Midterm Results of a Prospective Trial

To determine feasibility, safety, and midterm patency of a monorail balloon stent device for the treatment of renal artery stenosis (RAS). During a period of 30 months, 47 patients (with severe hypertension, n=45; renal insufficiency, n=20) with 50 cases of RAS and indications for stent implantation (calcified ostial lesion, n=41; insufficient percutaneous transluminal angioplasty, n=6; dissection, n=3) were enrolled into the prospective evaluation. After predilation, 59 stents (Rx-Herculink 4 mm, n=2; 5 mm, n=19; 6 mm, n=35; 7 mm, n=3) were implanted under manometer control with use of the long-sheath technique (5 F; 6 F for 7-mm stents) via a femoral (n=44) or transbrachial approach (n=6). Parameters of hypertension and renal insufficiency were determined before and after the procedure and for a maximum of 18 months. Restenosis rate was determined with color duplex ultrasonography. Renal artery stent placement (mean diameter, 5.7 mm; mean length, 16 mm) was technically successful in all cases (100%). Mean blood pressure and serum creatinine level decreased from 177/93 mm Hg to 145/78 mm Hg and from 1.8 mg/dL to 1.5 mg/dL, respectively. Within 48 hours after the implantation, acute occlusions occurred in two patients, supposedly triggered by cholesterol embolization. Primary and primary assisted patency rates were 87% and 92% at 6 months and 75% and 84% at 18 months. Renal artery stent placement with the rapid-exchange monorail system is a safe procedure with promising patency rates. In combination with the long-sheath technique, adequate control of stent deployment is guaranteed during the entire intervention. The low profile of the device facilitates the use of small sheaths (5 F) to minimize access-site complications.

Endovascular stenting to treat chronic long-segment inferior vena cava occlusion

Chronic inferior vena cava (IVC) occlusion is often associated with debilitating symptoms. Supportive therapy is the treatment offered to most patients, often with poor symptom control. Patients have had to learn to cope with the sequelae of the syndrome and to accept lifelong disability and pain. This may no longer be the case, because endovascular procedures have emerged as a promising alternative for treatment of chronic IVC occlusion. We present 2 case reports of long-standing long-segment IVC occlusion successfully treated with endovascular procedures that incorporated progressive balloon dilation and stenting. The remarkably rapid relief of pain and swelling and overall improvement in quality of life warrants attempts to correct the condition in other patients with IVC occlusion.

Can therapeutic ultrasound influence the regeneration of peripheral nerves?

An experimental study of the influence of the therapeutic ultrasound on the regeneration of the sciatic nerve submitted to a controlled crush injury was carried out in rats. Twenty female Wistar rats weighing 250 g on average were used and divided into two groups of 10 animals each, respectively, submitted to: (1) crush injury followed by ultrasound irradiation and (2) crush injury only. Under general anaesthesia the sciatic nerve was exposed on the right thigh and crushed with a device especially developed and built for this purpose, with a 15,000 g constant load for 10 min, affecting a 5 mm-long segment of the nerve proximal to its bifurcation. Pulsed ultrasound irradiation (1:5, 1 MHz, 0.4 W/cm 2, 2 min duration) was started the day after the operation and repeated for 10 consecutive days. The sciatic functional index (SFI) was evaluated at weekly intervals up to the third week, when the animal was killed for histologic and nerve fiber density studies of the sciatic nerve carried out on the lesion site and on the segments immediately proximal and distal to it. The SFI progressively improved for both treated and untreated nerves but in a more marked and significant way for the treated nerves (73 and 55%, respectively). Nerve fiber density did no return to normal in either case but was significantly higher in the treated nerves, with predominance of small diameter thin myelin sheath fibers typical of nerve regeneration in the treated nerves, as opposed to large diameter thin myelin sheath fibers in the untreated nerves. The authors conclude that low intensity therapeutic ultrasound enhances nerve regeneration, as demonstrated with significance on the 21st postoperative day.

Is there a role for small-diameter ureteral access sheaths? Impact on irrigant flow and intrapelvic pressures

Objectives To evaluate irrigant flows and intrapelvic pressures with small-diameter access sheaths. Ureteral access sheaths improve irrigant flow and decrease intrarenal pelvic pressures during flexible ureteroscopy. However, no comparisons of individual sheaths have been conducted. Previous studies have demonstrated more favorable results with the 12F sheath than with the 10F sheath. Methods Ureteral access sheaths were tested ex vivo in porcine kidneys. An 18F angiocatheter was placed in the renal pelvis and connected to a Hewlett Packard Gauss Pressure transducer. Irrigant was maintained at 100 mm Hg pressure. Irrigant flow and intrapelvic pressures were measured with three flexible ureteroscopes at baseline and using each of four 10F sheaths, with the sheaths positioned in the middle ureter and the ureteroscopes positioned in the renal pelvis. The pressure at which irrigant efflux through the sheath occurred and the rate of irrigant efflux through the access sheath were measured. Results Intrapelvic pressures measured greater than 40 mm Hg, and irrigant flows remained at less than 15 mL/min when the Olympus URF-P3 and Storz 11274AAU flexible ureteroscopes were tested with all four sheaths. The intrapelvic pressures, irrigant inflow, and irrigant efflux with the Wolf 7325.172 (7.5F) flexible ureteroscope were optimized in combination with the Cook Peelaway 10F and Applied Access 10F sheaths. Conclusions Small ureteral access sheaths should be used only with the Wolf 7325.172 flexible ureteroscope. The Cook Peelaway (10F) and Applied Access (10F) sheaths offered the greatest increase in irrigant flow and decrease in intrapelvic pressures.

Does a “split” stent make sense?

In the preceding article, Ewert et al. [1] describe a technique in which they implant in piglets stents that have been split longitudinally. The sides of the stent were reattached using absorbable sutures that, when absorbed, allow for further expansion of the stents. These modified stents were placed in normal inferior venae cavae, descending aortae, or pulmonary arteries through a 5 Fr sheath. The animals were recatheterized 14–23 weeks later. In no instance was a pressure gradient recorded across the stented vessel segment. In 10 of 20 stents, there was angiographic appearance of narrowing of no more than 10% of the vessel diameter. These stents were redilated successfully, although the definition of “successful” is not given. The authors conclude that this “may be a promising new device for the permanent treatment of stenotic vessels in infancy and childhood.” The primary advantage of this technique seems to be that the stents can implanted through small (5 Fr) sheaths. However, one must interpret this report with caution. As the authors themselves point out, these stents were implanted in native nonstenotic vessels. Whether similar success is achievable in diseased stenotic vessels is not clear. Additionally, the fact that the radial strength of this split stent will be disturbed could be of major concern. Redilating, especially using high-pressure balloons, is likely to deliver outward forces to the stenotic vessel in a nonuniform manner. This nonhomogeneity of force coupled with the increased elastic filaments, which were stretched and widely separated as demonstrated in the present report, raises serious questions about the use of this technique in small infants with diseased vessels. This concern would also be true for a stent with a single longitudinal split, as described by Ing et al. [2]. Finally, the fact that the two halves of the stents described in the present report had separated with growth of the vessel raises the question as to how much they are responsible for the lack of stenosis in the older animals. Another stent with a novel design described by Forbes et al. [3] has many of the characteristics desirable in a stent that can be redilated to a larger size in growing children. This stent, which is not split, requires a 6 Fr sheath for implantation, but it is flexible enough to be implanted in the pulmonary arteries and can be dilated up to 20 mm. Because of the design of the stent, interposing omega hinges between cells, it maintains uniform radial strength with little shortening on subsequent dilation, unlike a similar stent without the newer design [4]. The issue of implanting stents in infants and small children has been problematic because of the inability to dilate the stents to an adequate size as the child grows. Innovations, such as the one described in this report, have begun to address this issue. As with many other developments in the catheterization laboratory, it is only a matter of time before this issue is resolved. Whether the right technique will include use of a split stent or some other design remains to be seen.

Unique distributions of the gap junction proteins connexin29, connexin32, and connexin47 in oligodendrocytes

Oligodendrocytes of adult rodents express three different connexins: connexin29 (Cx29), Cx32, and Cx47. In this study, we show that Cx29 is localized to the inner membrane of small myelin sheaths, whereas Cx32 is localized on the outer membrane of large myelin sheaths; Cx29 does not colocalize with Cx32 in gap junction plaques. All oligodendrocytes appear to express Cx47, which is largely restricted to their perikarya. Cx32 and Cx47 are colocalized in many gap junction plaques on oligodendrocyte somata, particularly in gray matter. Cx45 is detected in the cerebral vasculature, but not in oligodendrocytes or myelin sheaths. This diversity of connexins in oligodendrocytes (in different populations of cells and in different subcellular compartments) likely reflects functional differences between these connexins and perhaps the oligodendrocytes themselves.

Antenna analysis in magnetized plasma via particle-in-cell simulation

We for the first time applied electromagnetic Particle-In-Cell (PIC) computer simulations to analyze the antenna characteristics in magnetized plasma. In a three-dimensional simulation space, we placed a dipole antenna which is a conducting current line in a magnetized plasma. By providing a Gaussian pulse as an input power to the center of the antenna and observing the current induced at the power feeding point, we obtain the input impedance of the antenna as a function of frequency. We particularly examined the electron kinetic effects on the antenna impedance such as electron temperature and electron evacuated region (ion sheath) formed around the antenna. It is confirmed that the most obvious resonance point is the local Upper Hybrid Resonance frequency. As the electron temperature increases, the resonance frequency also increases in accordance with the modification of dispersion relation for the UHR branch. We also examined the antenna impedance variation by changing the size of the electron evacuated region or ion sheath created around the antenna. We could confirm that the antenna resonance near the local UHR frequency is sharp for the small sheath while the profiles of the impedance approach to those of vacuum case as the sheath becomes large. The resonance frequency also decreases because the plasma density also decreases in the vicinity of the antenna.

In-Hospital Complications of Percutaneous Intraaortic Balloon Counterpulsation

Complications related to intraaortic balloon counterpulsation pumping (IABP) remain a problem despite the development of small caliber balloon catheter shafts and introducer sheaths. The authors report their experience in counterpulsation-related complications of 201 consecutive patients who underwent 212 percutaneous counterpulsation balloon insertions from June 1989 to June 1996 by use of balloons with 8-9.5 French shafts. Of these, 82% were men and 36 (18%) were women, with a mean age of 61 +/-12 years. Indications for counterpulsation were acute myocardial infarction (AMI) (67%), severe left ventricular failure without AMI (20%), dilated cardiomyopathy (4%), unstable angina (3%), high-risk supported percutaneous coronary angioplasty (2%), and others (4%). IABP was instituted at the bedside in the intensive care unit in 82 patients (39%) and in the catheterization laboratory in 130 (61%). Median duration of counterpulsation was 48 hours (range 30 minutes to 25 days) with successful weaning from counterpulsation in 70% (148 of 212) of procedures. Overall in-hospital mortality rate was 45% (90 of 201). The overall complication rate was 22/212 (10.4%). Major complications were present in 10/212 procedures (4.7%): 6 patients with limb ischemia (1 death directly attributed to this complication, 1 with associated septicemia and limb amputation, 3 requiring surgical thromboembolectomy, and 1 with persistent limb ischemia treated medically until his death caused by intractable left ventricular failure), 2 with important bleeding (1 fatal despite vascular surgical repair and 1 requiring blood transfusion) and 2 with balloon rupture requiring vascular surgery. Minor complications were present in 12 procedures (5.7%), 6 with limb ischemia, 3 with local bleeding, and 3 with catheter dysfunction. All of these resolved after balloon removal and required no further intervention. When limb ischemia did develop it occurred after a median delay of 24 hours following balloon insertion (range 2 to 98 hours). The only predictor of limb ischemia among baseline clinical and procedure-related variables was an age greater than 60 years. Compared with previous recent studies, the rate of complications observed in this study performed with small balloon catheters was acceptably low. Limb ischemia was the most frequent complication, often occurred early, and required further intervention in half the cases.

A rapid-exchange monorail stent system for salvage of failing femoropopliteal bypass grafts.

To analyze the safety and effectiveness of a new monorail stent system for the treatment of failing femoropopliteal bypass grafts. Acute distal occlusions or stenoses of femoropopliteal bypass grafts were treated with balloon-expandable stents (13 or 18-mm diameter) pre-mounted on a monorail balloon catheter system. The delivery system was assessed subjectively for (1). compatibility with the sheath, (2). lesion crossing potential, (3). radiopacity, (4). flexibility of the catheter, (5). adequacy of stent expansion, and (5). balloon refolding. In 8 failing bypass grafts with distal lesions, the delivery system successfully deployed the stent at the desired location. Sheath compatibility, catheter flexibility, lesion crossing, and stent expansion were rated "excellent" by all examiners for the 18-mm device. Radiopacity of the mounted stent was graded "good" before and during positioning, but only "sufficient" following expansion. For this type of lesion, the investigators rated the overall performance of the device superior to conventional "over-the-wire" systems. The monorail balloon-expandable stent delivery system provides rapid introduction of the device over the guidewire, and its low profile facilitates the use of small sheaths to minimize access-site complications.

Changes in the expression and localization of the paranodal protein Caspr on axons in chronic multiple sclerosis.

The presence of intact paranodal junctions on myelinated axons in the CNS and PNS is crucial for both myelin sheath attachment and saltatory impulse conduction. The axonal glycoprotein contactin-associated protein (Caspr) is expressed in the paranodal region and plays an important role in the creation and maintenance of these adhesive junctions. In the present study, antibodies to Caspr were used to assess the integrity of paranodal junctions on myelinated axons in brain and spinal cord tissue from subjects with longstanding multiple sclerosis, a neurological disorder that affects both myelin and axons. Triple immunofluorescence combined with confocal laser scanning microscopy showed that axons in the demyelinated centre of the 36 brain and 16 spinal cord multiple sclerosis lesions studied were devoid of Caspr immunoreactivity, suggesting that axons down regulate the expression of Caspr following demyelination. Additional data indicated that Caspr reappears in the paranodal region with the formation of new myelin sheaths. Immuno labelling further revealed that Caspr on myelinated axons in border regions was often no longer concentrated in the paranodal region, but was also present in the internodal region-a phenomenon particularly common in the borders of the more chronic lesions in the collection. Myelinated axons with long Caspr-positive stretches were often present at a considerable distance from the lesion edges. These findings raise the possibility that the aberrant location of Caspr is an early sign of impending myelin loss. This would imply that demyelination continues at a slow rate in established lesions. The diameters of Caspr-positive structures on some myelinated axons near the lesion edges were also increased. Moreover, the gap between individual myelin sheaths on these apparently swollen axons was widened occasionally and a very small myelin sheath plus additional Caspr-positive structures had sometimes formed in the enlarged space. This finding thus suggests that the formation of new myelin in multiple sclerosis is not only induced following the loss of complete internodes but also in response to broadening of the nodal region. Interestingly, alterations in the expression and localization of Caspr were observed in tissue from both subjects with the primary and secondary progressive form of multiple sclerosis. In summary, the present study provides immunohistochemical evidence that paranodal junctions on some myelinated axons in the borders of lesions of patients with chronic progressive multiple sclerosis are no longer intact. This may impair saltatory impulse conduction and lead to further myelin loss, thereby contributing to disease progression in multiple sclerosis.

Altered histology of the thymus and spleen in contaminant‐exposed juvenile American alligators

Morphological differences in spleen and thymus are closely related to functional immune differences. Hormonal regulation of the immune system has been demonstrated in reptilian splenic and thymic tissue. Spleens and thymus were obtained from juvenile alligators at two reference sites in Florida, USA: Orange Lake and a National Wildlife Refuge, Lake Woodruff, as well as from a contaminated lake, Lake Apopka. Lake Apopka has been extensively polluted with agricultural pesticides. Tissues were prepared for histological analysis to determine if previously detected endocrine abnormalities associated with contaminant exposure might also be reflected in morphological differences in splenic and thymic structures important for immunological response. Similar tissues were taken from captive-raised juvenile female alligators (3 years old) that were hatched from eggs collected on Lake Woodruff and Lake Apopka. Differences in thymic ratios (medulla/cortex) were found among alligators collected from the two lakes (P = 0.0051). Alligators from Lake Apopka had smaller thymic ratios than animals from either reference lake. Males from Lake Woodruff had significantly smaller lymphocyte sheaths in the spleen than females (P = 0.0009), indicative of a normal sexual dimorphism. Lymphocyte sheath width differed among females obtained from the three lakes, with females from Lake Apopka having the smallest sheath width and those from Orange Lake having the largest. Malpighian body area was largest in alligators from Orange Lake, intermediate in Lake Woodruff, and smallest in Lake Apopka. In contrast to that observed for wild-caught animals, no difference was found in the thymic medulla/cortex ratio of captive-raised female alligators (P = 0.378). Captive-raised female alligators from Lake Apopka and Lake Woodruff displayed lake-associated differences in lymphocyte sheath width as observed in wild animals; Lake Apopka alligators had smaller lymphocyte sheath width compared to Woodruff alligators (P = 0.0396). In contrast to wild-caught animals, area of the Malpighian bodies did not differ by lake in the captive-raised female alligators (P = 0.066). The enlarged thymic cortex suggests a change in T-lymphocyte maturation within the thymus of alligators from a contaminated environment, Lake Apopka. The results point to alterations in the histology of the thymus and spleen. Further studies are required to examine the functional significance of these observations.

Multiple ion-focusing effects in plasma immersion ion implantation

In plasma immersion ion implantation, the sample is negatively biased and a plasma sheath forms. Ions are accelerated to the sample surface through this sheath. The electric field contours dictate the shape of the plasma sheath that wraps around corners and tends to be smoother and rounder than the surface topography, for instance, at a sharp corner. Our theoretical and experimental studies reveal ion flux focusing effects leading to lateral nonuniformity of the incident ion dose. Ion focusing occurs not only at the sample edge but also in the central region even for a planar sample (wafer). In this work, we numerically and experimentally investigate this ion focusing effect and ion dose nonuniformity. A simple geometric model is also presented in this letter to understand the mechanism. The results demonstrate that ion focusing originates from plasma sheath convergence that is time and space dependent. Consequently, multiple ion focusing may occur at different local sites when the target shape and processing parameters vary, and a small plasma sheath relative to the target is of paramount importance for uniform implantation.

Connexin29 Is Uniquely Distributed within Myelinating Glial Cells of the Central and Peripheral Nervous Systems

Although both Schwann cells and oligodendrocytes express connexin32 (Cx32), the loss of this connexin causes demyelination only in the PNS. To determine whether oligodendrocytes might express another connexin that can function in place of Cx32, we searched for novel CNS-specific connexins using reverse transcriptase-PCR and degenerate primers. We identified Cx29, whose transcript was restricted to brain, spinal cord, and sciatic nerve. Developmental expression of Cx29 mRNA in the CNS paralleled that of other myelin-related mRNAs, including Cx32. In the CNS, Cx29 antibodies labeled the internodal and juxtaparanodal regions of small myelin sheaths, whereas Cx32 staining was restricted to large myelinated fibers. In the PNS, Cx29 expression preceded that of Cx32 and declined to lower levels than Cx32 in adulthood. In adult sciatic nerve, Cx29 was primarily localized to the innermost aspects of the myelin sheath, the paranode, the juxtaparanode, and the inner mesaxon. Cx29 displayed a striking coincidence with Kv1.2 K(+) channels, which are localized in the axonal membrane. Both Cx29 and Cx32 were found in the incisures. Cx29 expressed in N2A cells did not induce intercellular conductances but did participate in the formation of active channels when coexpressed with Cx32. Together, these data show that Cx29 and Cx32 are expressed by myelinating glial cells with distinct distributions.

Percutaneous Endovascular Abdominal Aortic Aneurysm Repair

In this prospective, nonrandomized study, we compared outcome with percutaneous femoral artery closure to that with open femoral arteriotomy in 95 patients who underwent endovascular AAA repair. Devices were introduced using 22 Fr and/or 16 Fr sheaths. The 8 Fr/10 Fr Perclose devices (Perclose Inc., Redwood City, CA) were used in an off-label "preclose technique." Thirty-three patients had bilateral open femoral arteriotomies, 44 patients had bilateral attempted percutaneous closure, and 18 patients had open femoral arteriotomy on one side and attempted percutaneous closure on the other side. Percutaneous closure was successful in 85% (47/55) of 16 Fr sheaths and 64% (29/45) of 22 Fr sheaths (p < 0.027). Bilateral percutaneous closure was successful in 63% (28/44) of patients. Conversion to open femoral arteriotomy due to bleeding occurred in 24 of 106 percutaneous attempts. There were no dissections, arterial thromboses, or pseudoaneurysms associated with percutaneous arterial closure. Wound complications were seen in 3.6% (3/84) of open arteriotomies and 0.9% (1/106) of all percutaneous attempts and arterial closures (p > 0.05). Gender, previous femoral access, obesity, and iliac occlusive disease were not predictive of percutaneous failure. Procedural success for percutaneous AAA repair is affected by sheath size. Devices delivered through 16 Fr or smaller sheaths will have successful femoral artery closure rates of at least 85%.

RENAL PARENCHYMAL INJURY AFTER STANDARD AND MINI PERCUTANEOUS NEPHROSTOLITHOTOMY

Mini percutaneous nephrostolithotomy was developed for use in children and in adults with a reduced renal reserve to minimize the morbidity and renal parenchymal damage presumed to occur with traditional percutaneous nephrostolithotomy. We compared the extent of renal injury incurred by different sized nephrostomy tracts in female farm pigs undergoing 11 or 30Fr percutaneous nephrostomy. Bilateral percutaneous nephrostomy was attempted via a mid or lower pole calix under fluoroscopic guidance in 6 pigs. In 2 pigs the procedure was unsuccessful on 1 side, leaving 5 successfully established nephrostomy tracts on each side. In each pig the right percutaneous tract was dilated with a 28Fr dilating balloon and a 30Fr Amplatz working sheath (Cook Urological, Spencer, Indiana) was positioned in the collecting system. On the left side an 11Fr sheath (Cook Urological) was placed. The sheaths were removed after 1 hour and nephrostomy tubes (22Fr on the right and 8Fr on the left side) were left in place overnight and then removed. Six weeks later the pigs were sacrificed and the kidneys were harvested. The nephrostomy tracts were identified grossly and examined microscopically, and the fibrotic scar was measured using digital analysis. The volume of scar was estimated using the calculated volume of a cylinder. At kidney harvest all 10 kidneys appeared grossly normal. No intra-abdominal urine collection or perirenal hematoma was noted. Mean estimated scar volume of the 30 and 11Fr tracts was 0.29 and 0.40 cc, which translates into a mean fractional loss of parenchyma of 0.63% and 0.91%, respectively (p not significant). Renal parenchymal damage resulting from the creation of a nephrostomy tract is small compared to overall renal volume regardless of the size of the nephrostomy tract. Consequently there is no advantage to the use of a small access sheath based on renal scarring alone.

Achieving femoral artery hemostasis after cardiac catheterization: a comparison of methods

Cardiac catheterization is a common procedure that involves the introduction of a small sheath (5F-8F) into the femoral artery for insertion of other diagnostic catheters. After cardiac catheterization, local compression of the femoral artery is required to prevent bleeding and to achieve hemostasis. Traditional methods of achieving hemostasis require significant time and close supervision by medical personnel and can contribute to patients' discomfort. VasoSeal is a recently developed device that delivers absorbable collagen into the supra-arterial space to promote hemostasis. To compare outcomes between patients receiving a collagen plug and patients in whom a traditional method of achieving hemostasis was used after diagnostic cardiac catheterization. An outcomes tracking tool was used to analyze the medical records of 95 patients in whom a traditional method was used (traditional group) and 81 patients in whom VasoSeal was used (device group) to achieve hemostasis. Complications at the femoral access site, patients' satisfaction, and times to hemostasis, ambulation, and discharge were compared. Hematomas of 6-cm diameter occurred in 5.3% of the traditional group; no complications occurred in the device group. The device group also achieved hemostasis faster and had earlier ambulation (P < .001). Patients in the device group were discharged a mean of 5 hours sooner than patients in the traditional group (P < .05). No significant differences were found in patients' satisfaction. VasoSeal is a safe and effective method of achieving hemostasis after cardiac catheterization that can hasten time to hemostasis, ambulation, and discharge.