Fixation Methods for Implantable Port Chamber: Comparative Study Using Glue, Self-stabilizing Leg and Suture Fixations in Rabbits

Objective

To evaluate the fixation strength and tissue reaction of the glue fixation and self-stabilizing leg fixation methods and to compare the results with those of the conventional tagging suture fixation method.

Materials and Methods

Twelve healthy rabbits were selected and three different methods of implanting the port chamber were employed on the back of each rabbit. A total of thirty six port chambers were implanted with these three different methods, viz. the glue fixation method using tissue adhesive, the self-stabilizing leg method using a self-expandable stabilizing leg, and the suture fixation method. The fixation strength and the gross and histopathologic changes of each fixation method were evaluated at three days, one week, two weeks and four weeks after port implantation.

Results

The glue fixation method showed a good fixation strength, which was similar to that of the tagging suture method (p = 0.3486). Five of the six ports (83%) implanted with the glue fixation method which were examined after two weeks showed cracks on the external surface, but this had no adverse effects on their function. A large amount of granulation tissue reaction was found at the bottom of the chamber (p = 0.0025). The fixation with the self-stabilizing leg showed relatively lower fixation strength (p = 0.0043), but no turning-over of the chamber occurred. The fixation strength improved with time after the first week, and minimal granulation tissue reaction was observed with this method.

Conclusion

The glue fixation method exhibited equal fixation strength compared to the suture fixation, but showed cracking and a large amount of granulation tissue, whereas the fixation with a self-stabilizing leg showed weaker fixation strength.     

Evaluation of venous injury caused by a percutaneous mechanical thrombolytic device

Purpose To study venous injury caused by a prototype percutaneous mechanical thrombolytic device.Methods Simulated thrombolysis was performed using the device, or the Fogarty balloon catheter (FBC) as control, in the infrarenal inferior vena cava (IVC) of 40 New Zealand white rabbits. Venous injury was evaluated by cavography, Evans blue dye staining, and histology at 0, 1, and 6 weeks postprocedure.Results Both devices resulted in near complete endothelial denudation acutely. No differences in reendothelialization were noted at any time in the proximal and mid-IVC, but there was significantly greater reendothelialization in the distal IVC in the rabbits treated 6 weeks earlier with the device (p 0.04). Additionally, the inner luminal diameter at necropsy for the 1-week rabbits treated with the FBC was significantly narrower in the distal and middle sections of the IVC when compared with the device (p 0.02 for both segments). There was no luminal diameter difference at 0 or 6 weeks.Conclusion Based on a rabbit model, venous injury from the device was found to be similar to, and in the distal IVC less than, the routinely used FBC.     

兔VX2肝癌模型的改良制作及肝血管造影技术探讨

目的：探讨兔VX2肝癌模型建立方法的改良及肝血管造影技术的应用。方法：健康新西兰大白兔共40只,分别采用常规开腹穿刺接种法及改良开腹穿刺接种法。将种植成功的实验兔于第2、3周分别肝动脉、门静脉造影检查。结果：36只实验兔成功建立兔VX2肝癌模型。改良法模型种植成功率较高（95%,19/20）,发生肝内播散转移及腹腔或网膜种植几率小（P〈0.05）。第2周均成功施行了经导管股动脉-肝动脉造影术（36/36,100%）,开腹行门静脉直接穿刺造影成功率97.22%（35/36）。第3周时实际存活实验兔26只均成功开腹行肝动脉及门静脉直接穿刺造影检查（26/26,100%）。结论：①采用改良方法制作的兔VX2肝癌模型,种植成功率较高,所建模型较稳定;②本研究所采用肝动脉及门静脉造影检查策略切实可行,且不影响肝脏血流动力学变化。     

Radiofrequency Ablation of the Gastrointestinal Tract with a Stent-Like Electrode: Experimental Study

Objective

To assess the technical feasibility of a newly designed stent-like electrode in rabbits.

Materials and Methods

A stent-like electrode was knitted from a single thread of nitinol wire and interconnected to a generator using similar wire. In order to gauge the extent of radiofrequency ablation (RFA), we measured the depth of the ablated area in cow liver using a combination of 180-sec time intervals and 20-watt power increments. For data processing, Cox regression analysis was used. RFA was also applied to the small intestine of rabbits using this stent-like electrode under six different sets of conditions: 10 watts for 1 min, 10 watts for 2 mins, 20 watts for 1 min, 20 watts for 2 mins, 30 watts for 1 min, and 30 watts for 2 mins. To determine the gross and microscopic findings, six animals were sacrificed immediately after the procedure and the results obtained under the different sets of conditions were correlated. Eight rabbits were monitored for 4 weeks prior to sacrifice.

Results

For both ex-vivo and in-vivo ablations, the depth of the thermal lesion showed linear correlation with both the duration of RFA and the power applied. RFA of the duodenum was technically successful in all 14 rabbits. The acute changes occurring in the rabbits'' small intestine included color change, cytoplasmic denaturation, fibrin deposition and hemorrhage, among which hemorrhage of the mucosal layer was the earliest finding. RF ablation for 2 mins at 30 watts caused serosal hemorrhage. The gross and histologic changes occurring showed close correlation under all six sets of conditions.

Conclusion

Use of the stent-like electrode proves technically feasible but to determine the nature of the chronic change occurring in the gastrointestinal tract after RF ablation, further investigation and long-term follow-up in animals are required.     

Retrieval of an embolization coil from the internal carotid artery using the Amplatz Microsnare Retrieval System

An unusual case of unintentional release of an embolization coil into the proximal internal carotid artery is reported. The coil migrated and lodged distally in the petrous portion of the internal carotid artery during initial removal attempts using a regular nitinol loop snare. The coil was retrieved with the Amplatz Nitinol Microsnare system.     

A new catheter configuration for selective antegrade catheterization of the superficial femoral artery: Technical note

A new 5 F catheter configuration is presented with a very short, 90 degrees angled tip that allows safe catheter tip rotation near the puncture site. This facilitates catheterization of the superficial femoral artery and permits easy conversion of a retrograde into an antegrade guidewire placement after puncture of the common femoral artery.     

Experimental impeller fragmentation of iliocaval thrombosis under tulip filter protection: Preliminary results

Purpose To assess the efficacy of catheter fragmentation of massive caval thrombosis and of filter protection against procedure-related pulmonary embolism. Methods In 10 sheep, a self-expanding tulip-shaped filter made from Wallstent mesh (diameter 25 mm) was introduced from the right jugular approach into the proximal inferior vena cava. Experimentally induced massive iliocaval thrombosis was fragmented by an impeller catheter (expanded diameter 14 mm), which was advanced coaxially through the sheath of the expanded filter. Post-procedural cavography and pulmonary angiography were performed to document the extent of caval recanalization and pulmonary embolism. Results In all cases, impeller fragmentation cleared the inferior vena cava and the iliac veins of thrombi completely. Fragments washed downstream were trapped in the filter. In two of the first cases, parts of the clots caused pulmonary embolism before the filter was in place. Further events were avoided by a modification of the experimental setup. Except for some small peripheral perfusion defects in two cases, pulmonary angiograms did not show any incidence of pulmonary embolism. Conclusion Our preliminary results suggest that impeller fragmentation of iliocaval thrombi under tulip filter protection is effective and does not cause significant pulmonary embolism.     

放射性125I粒子植入对兔坐骨神经放射性损伤的实验研究

目的 观察125I粒子植入后不同时间家兔坐骨神经组织形态及功能的变化.方法 选健康新西兰家兔30只,使用信封法分为2周、2个月及4个月3组,每组10只,直视下在兔的实验侧坐骨神经旁植入125I粒子10粒,对照侧植入无放射活性空粒子10粒.按三维治疗计划系统(treatment plan system,TPS)计划设计布源,90%处方剂量集中在所研究的坐骨神经局部.术后2周、2个月及4个月行双侧坐骨神经神经电生理测定及大体观察、光镜观察和电镜观察.将同为4000放大倍数的电镜照片分为100(10×10)个方格,出现非特异性改变占1个方格则计数为1%.所测指标之间的比较采用t检验和秩和检验.结果 2周、 2个月、4个月组兔实验侧坐骨神经的近心端动作电位强度分别为(0.52±0.26)、(0.60±0.19)、(0.48±0.17)V,对照侧分别为(0.59±0.19)、(0.60±0.15)、(0.53±0.13)V,差异无统计学意义(t值分别为0.91、0.03、0.67,P值均>0.05),2周、2个月、4个月组兔实验侧坐骨神经远心端动作电位强度分别为(0.51±0.15)、(0.52±0.11)、(0.53±0.15)V,对照侧分别为(0.52±0.10)、(0.56±0.12)、(0.54±0.10)V,差异无统计学意义(t值分别为0.25、0.74、0.17,P值均>0.05);2周、2个月、4个月组兔实验侧坐骨神经近心端动作电位最大振幅分别为(13.18±4.09)、(12.78±4.42)、(12.09±1.20)mV,对照侧分别为(10.55±4.21)、(10.31±4.22)、(12.88±3.54)mV,差异无统计学意义(t值分别为1.57、1.36、0.50,P值均>0.05),2周、2个月、4个月组兔实验侧坐骨神经的远心端动作电位最大振幅分别为(11.18±3.38)、(11.68±3.21)、(12.52±3.09)mV,对照侧分别为(11.56±4.80)、(10.71±3.40)、(11.67±2.48)mV,差异无统计学意义(t值分别为0.29、1.01、0.55,P值均>0.05);2周、2个月、4个月组兔实验侧坐骨神经神经传导速度分别为(40.56±9.46)、(38.79±5.78)、(39.44±8.64)m/V,对照侧为(42.56±6.59)、(44.64±7.53)、(43.33±6.05)m/V,差异无统计学意义(t值分别为0.57、1.94、0.01,P值均>0.05).大体学观察和光镜观察实验侧坐骨神经病理学改变不明显;电镜观察可见到有髓神经鞘分层、塌陷、崩解等变性改变;神经鞘膜细胞和神经轴突内可见线粒体肿胀、空泡化.非特异性变化2周组为60%-70%,2个月组为50%左右,而4个月组下降到30%左右,3组比较差异有统计学意义(Z值均为-3.79,P<0.05).结论 该实验剂量下放射性125I粒子对家兔坐骨神经的组织影响以超微病理下的非特异性变化为主,对神经的生理功能影响微小.     

Ultrasound-guided percutaneous laser ablation of liver tissue in a rabbit model

The present report evaluates the efficacy and safety of percutaneous interstitial laser tissue ablation of the liver in nine New Zealand rabbits. A Nd: YAG laser was coupled to a quartz fibreoptic guide (600 m) with a flat tip. The fibre and a thermocouple were placed in the lumen of two Chiba needles (18G) and these were inserted into the liver 10 mm apart under ultrasound guidance. The laser was fired for 5 min at 1, 3 and 5 W power, respectively, in three groups of rabbits. There were no acute complications and all the rabbits except one survived until the established time of sacrifice. The procedure induced a cavity surrounded by a zone (about 10 mm) of coagulative necrosis. After 2 weeks a strong peripheral inflammatory response was evident and after 4 weeks a capsule of connective tissue enclosed the lesions. Our study seems to offer a safe and rapid technique producing a guaranteed kill radius for the treatment of small hepatic neoplasms. Correspondence to: C. M. Pacella     

Percutaneous fragmentation of pulmonary emboli in dogs with the impeller-basket catheter

A new catheter system for rapid percutaneous fragmentation of pulmonary emboli was tested in nine dogs. The system consisted of a high-speed rotating impeller, placed within the center of a self-expandable basket. Preformed radiopaque emboli were introduced via the right external jugular vein. In nine tests in five dogs, a single embolus was launched after the right pulmonary artery had been balloon occluded and the impeller-basket catheter had been positioned into the left pulmonary artery, Seven of nine emboli were completely fragmented, each within less than 10 s. In two tests, performed in two different dogs, the catheter was positioned after complete embolization of the left pulmonary artery. In both cases, the central pulmonary arteries could be fully, and the segmental arteries partly, recanalized. Mobility of the system within the pulmonary arteries was limited. There was no evidence of wall damage at the rotation site of the impeller. Free serum hemoglobin did not increase after treatment. We conclude that the device can be safely operated in the left pulmonary artery system of dogs. It causes no significant hemolysis, and is able to accomplish rapid recanalization of the central arteries. Due to limited steerability, occluded side branches cannot be treated consistently.     

Laboratory Investigations[cmFragmentation of Pulmonary Emboli: In Vivo Experimental Evaluation of Two High-Speed Rotating Catheters

Purpose: To test two over-the-wire systems for fragmentation of pulmonary emboli. Methods: In 11 dogs, 22 embolic occlusions of lobar or central pulmonary arteries were performed by injection of preformed emboli through a jugular vein sheath. A commercially available device (thrombolizer) and a modified version of the impeller catheter were introduced via the femoral vein and positioned at the embolus site. Results: Catheter placement at the site of the emboli was possible. In more than half of the cases a hydrophilic or an extra-stiff guidewire was necessary. The thrombolizer did not rotate properly with its original pneumatic drive and required a major modification. When sufficient rotation was provided, both fragmentation catheters were able to clear the occluded main arteries. Side branches were partly obstructed by the resulting fragments. Recanalization led to a reduction of the emboli-induced elevation of the pulmonary arterial pressure by two-thirds. Histology of the recanalized pulmonary artery segments revealed localized (impeller catheter) and widespread (thrombolizer) periarterial hemorrhage. Conclusion: Embolus fragmentation led to a hemodynamic improvement. The impeller catheter was less traumatic compared with the thrombolizer, which was technically insufficient.     

“Retroantegrade” catheterization of the branches of the femoral artery: Technical note

Antegrade catheterization is the preferred approach to angioplasty and selective fibrinolysis of branches of the femoral artery. A simple method of antegrade catheterization beginning with a retrograde puncture and using a new catheter is described. The method can reduce the number of punctures and manipulations needed for selective antegrade catheterization of the common femoral artery.     

In vivo evaluation of the adjustable temporary venous spring filter and the RF02 temporary filter: Comparative study

RATIONALE AND OBJECTIVES: The authors performed this study to compare the in vivo efficacies of the temporary venous spring filter and the RF02 filter in an animal model. MATERIALS AND METHODS: Either the spring filter or the RF02 filter was placed in the inferior vena cava of 10 pigs each, and two clots (5 x 20 mm) were funneled into the filters at 1-hour intervals. The second clots were funneled without removing the first clots captured by the filters. Clot-trapping ability, caval occlusion associated with the clot-trapping procedure, arterial blood gas concentrations, and changes in arterial and iliac venous pressures were evaluated. RESULTS: Placement of the RF02 filter caused elevation of iliac venous pressure with a maximum of 2.2 mm Hg (median) (n = 13, P = .003). Placement of the spring filter parallel to venous flow enabled capture of 90% (nine of 10) and 100% (six of six) of the first and second clots, respectively. The RF02 filter captured clots consistently. The difference between filters was not statistically significant. Both filters equally contributed to elevation of iliac venous pressure (median, 9.3 and 7.2 mm Hg [n = 9] with the spring filter and RF02 filter, respectively). Caval occlusion occurred in 17% (one of six) and 67% (six of nine) of animals after two clots were trapped in the spring filter and RF02 filter, respectively (P = .06). Other parameters were not influenced by the clot-trapping procedure. CONCLUSION: Although a larger version should be developed and better stability of the filter is needed, the spring filter proved to be an efficient filtering device and had a lower rate of caval occlusion compared with the RF02 filter.     

MR Imaging-Histopathologic Correlation of Radiofrequency Thermal Ablation Lesion in a Rabbit Liver Model: Observation during Acute and Chronic Stages

Objective

To determine the ability of MR imaging to detect the pathological changes occurring in radiofrequency (RF) thermal lesions and to assess its accuracy in revealing the extent of tissue necrosis.

Materials and Methods

Using an RF electrode, thermal lesions were created in the livers of 18 rabbits. The procedure involved three phases. In the acute phase, six animals were killed the day after performing thermal ablation with RF energy, and two on day 3. In the subacute and chronic phases, eight rabbits underwent percutaneous hepatic RF ablation. After performing MR imaging, two animals were sacrificed at 1, 2, 4, and 7 weeks after the procedure, and MR-pathologic correlation was performed.

Results

In the acute phase, the thermal ablation lesions appeared at gross examination as well-circumscribed, necrotic areas, representing early change in the coagulative necrosis seen at microscopic examination. They were hypointense on T2-weighted images, and hyperintense on T1-weighted images. Gadolinium-enhanced MR imaging showed that a thin hyperemic rim surrounded the central coagulative necrosis. In the subacute phase, ablated lesions also showed extensive coagulative necrosis and marked inflammation at microscopic examination. Beyond two weeks, the lesions showed gradual resorption of the necrotic area, with a peripheral fibrovascular rim. The size of lesions measured by MR imaging correlated well with the findings at gross pathologic examination.

Conclusion

MR imaging effectively demonstrates the histopathological tissue change occurring after thermal ablation, and accurately determines the extent of the target area.     

Influence of a dexamethasone-eluting covered stent on tissue reaction: an experimental study in a canine bronchial model

This study was designed to evaluate the feasibility and efficacy of a dexamethasone (DXM)-eluting, covered, self-expanding metallic stent to reduce tissue reaction following stent placement in a canine bronchial model. We placed a DXM-eluting, polyurethane-covered, self-expanding metallic stent (drug stent, DS) and a polyurethane-covered, self-expanding metallic stent (control stent, CS) alternately in each left main bronchus and left lower lobe bronchus in 12 dogs. The stents were 20 mm in diameter and length when fully expanded. The dose of DXM was approximately 36.7 mg in each DS, but was absent in the CS. The dogs were euthanased 1 week (n=4), 2 weeks (n=4) or 4 weeks (n=4) after stent placement. Histologic findings, such as epithelial erosion/ulcer or granulation tissue thickness, were obtained from the mid-portion of the bronchus, where the stent had been placed, and evaluated between DS and CS. There were no procedure-related complications or malpositioning of any of the bronchial stents. Stent migration was detected in one dog just before euthanasia 1 week following stent placement. Stent patency was maintained until euthanasia in all dogs. Epithelial erosion/ulcer (%) was significantly less in the DS (mean±standard deviation, 46.88±23.75) than in the CS (73.75±14.08) (P=0.026) for all time-points. There was a decrease in epithelial erosion/ulcer as the follow-up period increased in both DS and CS. The granulation tissue thickness (mm) was less in DS (2.63±2.05) than in CS (3.49±2.95), although the difference was not significant (P=0.751) for all time-points. There was a tendency toward an increase in granulation tissue thickness and chronic lymphocytic infiltration as the follow-up period increased in both DS and CS. In conclusion, DXM-eluting, covered, self-expanding metallic stent seems to be effective in reducing tissue reaction secondary to stent placement in a canine bronchial model.     

肝内门腔分流术支架与血管支架组织成分的对比研究

目的 对比研究经猪颈静脉肝内门腔分流术(TIPS)与血管支架术后组织成分的异同,为TIPS与血管支架再狭窄的形成机制及防治提供更多的信息.方法 对6只25 kg的家猪进行TIPS术,建立TIPS猪模型,并行髂静脉支架置入术.14～28 d后处死,取出肝脏TIPS组织及支架段静脉绀织做病理检查,包括大体标本检查、电镜检查,病理切片行HE染色,免疫组织化学(简称免疫组化)分析抗平滑肌肌动蛋门-α、细胞增殖核抗原(PCNA)、波形蛋白、肌球蛋白表达,蛋白印迹(Western blot)分析转化牛长因子-β(TGF-β)表达.将TIPS组织与血管支架组织进行上述多项指标的对比分析.所获数据进行Kruskal Wallis秩和检验.结果 动物处死时,6只猪有4只,TIPS通道出现不同程度再狭窄,其中有2只TIPS通道完全堵塞,而髂静脉支架置入术后静脉支架均通畅,仅见支架通道内壁为一薄层内膜组织覆盖,腔内尤狭窄.电镜检查,TIPS再狭窄组织较为稀疏,较多胶原基质与纤维,细胞成分少至中等量,细胞形态多样且不规则,可见平滑肌细胞、少量成纤维细胞及成肌纤维细胞,细胞含丰富分泌颗粒;TIPS支架通畅组织可见大量胶原纤维,含中等量的细胞成分,主要是成纤维细胞及平滑肌细胞,细胞器幕本正常.支架段静脉组织含大量胶原纤维,细胞成分较多,主要为成纤维细胞,平滑肌细胞较少.免疫组化检测:抗平滑肌肌动蛋白-α,TIPS再狭窄组织表达强阳性,TIPS通畅组织表达也较强,支架段静脉组织表达较强,但阿性细胞明显稀疏;PCNA在TIPS冉狭窄组织表达强阳性,在,TIPS通畅组织表达也较强,在支架段静脉组织表达明显较弱;波形蛋白在支架段静脉组织表达较强,在通畅的TIPS支架通道组织中为阳性表达,而在TIPS支架再狭窄组织中表达减弱;肌球蛋白在TIPS再狭窄组织表达为弱阳性,而在TIPS通畅的支架组织与支架段静脉组织表达更弱.Western blot检测TGF-β,支架段静脉组织、正常静脉组织对照、正常肝组织埘照、TIPS狭窄组织及TIPS通畅组织的吸光度比值(TGF-β/β肌动蛋白)中位数分别为0.23、0、0、 0.57、0.30,对所获条带的光密度比值进行统计学分析,差异有统计学意义(H=27.8,P＜0.01).结论 猪模型中,TIPS再狭窄组织中主要为抗平滑肌肌动蛋白-α阳性的平滑肌细胞增殖,细胞增殖迁移能力强,细胞型稳定件低;通畅的TIPS组织与支架段静脉组织相似,表达波形蛋白的成纤维细胞较多,细胞较稳定.     

Gadolinium phosphonates as MR imaging contrast agents: Physiologic effects in rabbit hearts

The hemodynamic effects of the diphosphonate terminus of a new infarct-avid magnetic resonance (MR) imaging agent, gadolinium-DTPA (diethylenetriamine-pentaacetic acid) HPDP (1-hydroxo-3-aminopropane-1,1-diphosphonate), and HEDP (hydroxyethyl-1,1-diphosphonate) (a simple diphosphonate terminus model) have been evaluated at MR imaging doses in both isolated and intact rabbit hearts. Rapid injections of the sodium salt of the diphosphonates reversibly depressed left ventricular developed pressure and its first derivative (dP/df) but did not affect the in vivo heart rate. Hemodynamic depression was prevented by the co-administration of two equivalents of calcium ion per diphosphonate terminus in the isolated heart and by either slow infusion or co-administration of one equivalent of calcium ion per diphosphonate terminus in the in vivo heart. Therefore, if these agents are to be used in MR imaging of acute myocardial infarction, appropriate measures should be taken to prevent negative inotropic effects.     

Clearance of liposomal gadolinium: in vivo decomplexation.

The contrast agents gadolinium-DTPA (diethylenetriaminepentaacetic acid), Gd-DOTA (tetraazacyclododecanetetraacetic acid), and Gd-HP-DO3A (1,4,7-tris[carboxymethyl]-10-[2' hydroxypropyl]-1,4,7,10-tetraazacyclododecane) are used in humans as extracellular contrast agents. Although free Gd+ ion is toxic, the intact Gd3+ complexes are rapidly excreted and are relatively nontoxic. Decomplexation with release of free gadolinium is a relevant clinical concern in patients with altered renal clearance. Blood pool contrast agents currently under development may have longer clearance half-lives and be more prone to decomplexation. The present study was designed to evaluate the clearance of liposomally encapsulated Gd3+ complexes (DTPA, DOTA, and HP-DO3A). The macrocyclic compounds had more rapid and complete clearance than DTPA (P less than .05). Parallel studies with carbon-14 and Gd-153-labeled complexes showed significant differences (P less than .05) in the amount of these isotopes retained in the heart, kidney, lungs, and spleen, providing strong supportive evidence for in vivo decomplexation.