Hemodialysis-related venous stenosis: treatment with ultrahigh-pressure angioplasty balloons

A Cost-Effective Approach to Resistant AV Fistula Stenosis: Successful Treatment Using Coronary OPN NC® Balloon in a Low-Income Setting

Stenosis in the anastomotic site or venous limb of an arteriovenous fistula (AVF) is the most frequent cause of AVF failure. Percutaneous angioplasty with a standard or high-pressure balloon is the first-line treatment for AVF stenosis due to its higher technical success rate (90%) and lower complication rate (4%). Almost 20% of stenosis cases are resistant or undilatable by regular-pressure balloon angioplasty due to fibrosis, leading to technical failure or restenosis. Alternative therapies, such as atherectomy devices or cutting balloons, are expensive and difficult to obtain in low-income developing countries. We successfully treated resistant AVF stenosis with a coronary OPN-NC® ultra-high-pressure balloon and produced a good angiographic result with technical success. Coronary hardware is easily available and relatively cheaper compared to dedicated peripheral balloons or devices in our country due to reuse, which can be a boon in such type of cases. According to the standard hospital protocol, Cathlab hardware was reused.

Do Balloon Catheters have a Different Radial Force Along Their Longitudinal Axis?

PURPOSE

This experimental study was designed to compare radial forces between the central portion and both ends of balloon catheters when dilating stenosis.

MATERIALS AND METHODS

Three balloon catheters of 6 and 8 mm in diameter and of variable length were tested: Mustang, Conquest, and Genoss PTA. Cylindrical modules to position balloon catheters and install the measuring tip during radial force measurements were made using a 3D printer. The measuring tip created 20% stenosis at the inner lumen. Both ends and center of the balloon catheter were located at the measuring tip. The radial force was measured after inflating the balloon catheter to the rated burst pressure.

RESULTS

For the different diameters and lengths of balloon catheters and cylinder sizes, the median inccenter, the radial rease in radial force at the distal end compared to the center was 16.5% (range: 9.8-35.2%) for Mustang, 12.4% (range: 10.3-25.5%) for Genoss, and 7.4% (range: -0.3-13.1%) for Conquest balloon catheters. Similarly, compared to that at the force at the proximal end was 10.8% greater (range: -2.9-18.3%) for Mustang, 9.9% greater (range: 3.9-22.3%) for Genoss, and 7.3% greater (range: -1.3-12.4%) for Conquest catheters.

CONCLUSION

The radial force is greater at both ends of the balloon than at the central portion, especially at the distal end. Dilation using the distal end of the balloon catheter is a practical method that can be applied in clinical practice without additional devices when encountering resistant stenosis, especially with semi-compliant balloons.

Endovascular tools for vascular access stenosis: Flow-chart proposal

Stenosis represents the most relevant arteriovenous fistula (AVF) pathology and can affects the entire conduit forming the fistula, from afferent artery to central venous vessels. Correction of vascular access stenosis significantly affects the survival and quality of life for end stage renal disease patients (ESRD) dependent on hemodialysis. Guidelines consider the procedure of percutaneous transluminal angioplasty (PTA) relevant for the primary treatment of these lesions with excellent results in restoring AVF immediately at the end of the procedure. From first AVF angioplasty in 1981 to now, wide scientific innovation has led to development of new devices, composed by different materials and technologies, specific for the site and the type of stenosis to be treated, able to manage resistant stenotic lesion and to reduce stenosis recurrences. International guidelines do not clearly specify all treatment possibilities in the individual case. In this review the authors want to provide specific information on most used devices for stenosis treatment based on literature evidence, showing when and where to use the various tools available with flow-chart treatment proposal.

A Prospective Multicenter Randomized Controlled Trial for Comparing Drug-Coated and Conventional Balloon Angioplasty in Venous Anastomotic Stenosis of Hemodialysis Arteriovenous Grafts

PURPOSE

To evaluate the efficacy and safety of drug-coated balloon angioplasty compared to conventional balloon angioplasty in the treatment of dysfunctional arteriovenous grafts.

MATERIALS AND METHODS

This prospective, multicenter, randomized clinical trial enrolled 190 patients with venous anastomotic stenosis in arteriovenous grafts at five participating hospitals. During pre-dilation, 4 patients dropped out due to ruptures requiring further treatment (n = 2) and residual stenosis of > 30% (n = 2). On successful pre-dilation with a 7 mm conventional balloon, patients were randomized to undergo either a 7 mm drug-coated balloon (n = 94) or conventional balloon angioplasty (n = 92). The primary out-come measure was target lesion primary patency at 3 and 6 months. The secondary out-come measures included target lesion primary patency at 12 months and access circuit primary patency at 6 and 12 months, clinical and technical success rates, and 12-month mortality differences between the groups.

RESULTS

The target lesion primary patency and access circuit patency rates at 3 and 6 months were significantly higher in drug-coated balloon angioplasty group as compared to conventional balloon angioplasty group. The technical and clinical success rates were 100% for both the groups. As a procedure-related complication, anastomotic site rupture occurred during pre-dilation in 4 cases. The number of deaths during the 12-month follow-up was one for each group. The number of early thrombotic events (at < 3 months) was significantly higher in the drug-coated balloon group (p = 0.002).

CONCLUSION

Drug-coated balloon angioplasty was more effective and safer for the treatment of dysfunctional arteriovenous grafts compared to conventional balloon angioplasty.

Multicenter Randomized Controlled Trial of APERTO-Paclitaxel Drug-Eluting Balloon Angioplasty Versus Standard Percutaneous Transluminal Angioplasty in Dysfunctional Hemodialysis Grafts and Native Fistulae

PURPOSE

to assess the safety and efficacy of APERTO-Paclitaxel-coated balloon angioplasty versus standard angioplasty for the treatment of dysfunctional hemodialysis shunts and native arteriovenous fistulae.

METHODS

consecutive patients with dysfunctional dialysis related to underlying efferent vein stenosis were included and randomized 1:1 to either APERTO-paclitaxel drug-coated balloon (study arm) or standard percutaneous transluminal angioplasty (control arm). Primary endpoint is time from treatment until dialysis access dysfunction according to standardized Kidney Disease Outcomes Quality Initiative (KDOQI)-guidelines and assessed by Kaplan-Meier survival curves and tested for significance with log-rank analysis. Secondary endpoints include device, technical, and clinical success of the index angioplasty procedure.

RESULTS

The study included 103 patients (n=51 study-group) with a de novo (n=33) dysfunctional native arteriovenous fistula (n=79) in the forearm (n=60). The majority of included patients were male with a mean age of 69.8 years, presenting with a dysfunctioning autologous arteriovenous fistula in the forearm. Device-related complications did not occur in any of the included patients. Functional hemodialysis access without need for re-intervention at 1 year after index procedure was found in n=10 (19.6%) and n=5 (9.6%) of patients treated with, respectively, paclitaxel drug-coated balloon and percutaneous transluminal angioplasty (p=0.612). A nonsignificant benefit of paclitaxel drug-coated balloon (n=5; 25%) over percutaneous transluminal angioplasty (n=1; 11%) was found (p=0.953) in de novo lesions in autologous fistulas.

CONCLUSION

APERTO-paclitaxel drug-coated balloon is a safe balloon catheter to manage dysfunctional hemodialysis access; however, longer period of adequate hemodialysis circuit functioning after endovascular index stenosis treatment, using APERTO-paclitaxel drug-coated balloon versus percutaneous transluminal angioplasty could not be demonstrated.

CLINICAL IMPACT

APERTO-paclitaxel drug-coated balloon catheter is a safe device to manage dysfunctional hemodialysis access. Compared to conventional angioplasty balloon, the APERTO drug-coated balloon will not result in longer period of adequate hemodialysis circuit functioning. A non-significant benefit of APERTO drug-coated balloon was found in de novo lesions in autologous fistulas.

Ultra-high pressure balloon angioplasty for pulmonary artery stenosis in children with congenital heart defects: Short- to mid-term follow-up results from a retrospective cohort in a single tertiary center

Objective

Balloon angioplasty (BA) has been the treatment of choice for pulmonary artery stenosis (PAS) in children. There remains, however, a significant proportion of resistant lesions. The ultra-high pressure (UHP) balloons might be effective in a subset of these lesions. In this study, we analyzed the safety and efficacy with short- to mid-term follow-up results of UHP BA for PAS in children with congenital heart defects (CHD) in our center.

Methods

This is a retrospective cohort study in a single tertiary heart center. Children diagnosed with PAS associated with CHD were referred for UHP BA. All data with these children were collected for analysis with updated follow-up.

Results

A total of 37 UHP BAs were performed consecutively in 28 children. The success rate was 78.4%. A significantly (P = 0.005) larger ratio of the balloon to the minimal luminal diameter at the stenotic waist (balloon/waist ratio) was present in the success group (median 3.00, 1.64-8.33) compared to that in the failure group (median 1.94, 1.41 ± 4.00). Stepwise logistic regression analysis further identified that the balloon/waist ratio and the presence of therapeutic tears were two independent predictors of procedural success. The receiver operating characteristic curve revealed a cut-off value of 2.57 for the balloon/waist ratio to best differentiate success from failure cases. Signs of therapeutic tears were present in eight cases, all of whom were in the success group. Perioperative acute adverse events were recorded in 16 patients, including 11 pulmonary artery injuries, three pulmonary hemorrhages, and two pulmonary artery aneurysms. During a median follow-up period of 10.4 (0.1-21.0) months, nine cases experienced restenosis at a median time of 40 (4-325) days after angioplasty.

Conclusions

The UHP BA is safe and effective for the primary treatment of PAS in infants and children with CHD. The success rate is high with a low incidence of severe complications. The predictors of success are a larger balloon/waist ratio and the presence of therapeutic tears. The occurrence of restenosis during follow-up, however, remains a problem. A larger number of cases and longer periods of follow-up are needed for further study.

A Water Balloon as an Innovative Energy Storage Medium

Soft rubbery materials are capable of withstanding large deformation, and stretched rubber contracts when heated. Additionally, rubber balloons exhibit non-monotonic pressure-volume curves. These unique properties have inspired numerous ingenious inventions based on rubber balloons. To the authors' knowledge, however, it is surprising that these properties have not inspired any study that exploits the elasticity of rubber balloons for energy storage. Motivated by these, this study examines the performance of water balloons as energy storage media. In each experiment, a single water balloon is implemented using a flat membrane, and it is subject to repeated inflation, heating, deflation, and cooling. Inflating the balloon deposits energy into it. The heating simulates the recycling of waste heat. The balloon delivers work during its deflation. Finally, the cooling completes the energy-storage cycle. The performance is evaluated in terms of the balloon's transferred energies, efficiencies, and service life. Simple as it is, a water balloon is actually an impressively efficient energy storage medium. The efficiency is 85-90% when a water balloon stores and releases energy at room temperature. Recycling waste heat can boost a balloon's efficiency beyond 100%, provided that the cost of the heat is negligible so that the heat is not taken as part of the input energy. However, heating shortens the service life of a balloon and reduces the total energy it can accommodate. By running fatigue tests on balloons, this study reveals the trade-off between a water balloon's efficiency and its longevity. These results shall serve as a useful guide for implementing balloon-based mechanical devices not limited to energy-storage applications.

Arteriovenous fistulas for hemodialysis: Brief review and current problems

The number of people worldwide living with end-stage renal disease is increasing. Arteriovenous fistulas are the preferred method of vascular access in patients who will require hemodialysis. As the number of patients with arteriovenous fistulas grows, the role of physicians who intervene who maintain and salvage these fistulas will grow in importance. This review aims to familiarize practitioners with the rationale for arteriovenous fistula creation, the detection of fistula dysfunction, and the state of the art on fistula maintenance and preservation. Current controversies are briefly reviewed.

Recent developments in endovascular interventions to sustain vascular access patency in haemodialysis patients

There is amassed evidence regarding the use of endovascular procedures for the treatment of vascular access stenosis and thrombosis. A review was conducted based on available randomized trials, cohort studies and retrospective analyses published after 2000 on endovascular treatment of dysfunctional and thrombosed vascular access, with an aim to illustrate the available device and procedural options. The use of paclitaxel-coated balloons, cutting balloons and covered stents is described in the field of vascular access stenosis. The broad spectrum of available devices and endovascular declotting procedures ranging from thrombolysis to thrombectomy is also discussed. Overall, in this review we demonstrate the increasing role of endovascular procedures in vascular access treatment and the improved patency outcomes provided by the implementation of novel endovascular devices. Moreover, the improvement of post-intervention primary patency rates after endovascular declotting procedures and the shift to more thrombectomy-dependent procedures over time is also highlighted. In conclusion, endovascular treatment of dialysis access stenosis and thrombosis has an established role, owing to the implementation of sophisticated devices, allowing, when needed, the simultaneous treatment of thrombosis and the underlying stenosis.

Comparing the 12-month patency of low- versus high-pressure dilation in failing arteriovenous fistulae: A prospective multicenter trial (YOROI study)

PURPOSE

This study was performed to investigate the effect of the balloon dilation pressure on the 12-month patency rate in patients with failed arteriovenous fistulas undergoing hemodialysis.

MATERIALS AND METHODS

In this multicenter, prospective, randomized trial, the 4-mm-diameter YOROI balloon was used for dilation of stenotic lesions. The balloons were inflated to a pressure of 8 atm (low-pressure group) or 30 atm to achieve complete expansion (high-pressure group). The 12-month patency rate after balloon angioplasty was analyzed by the Kaplan-Meier method and log-rank test and/or a Cox proportional hazard model. We also investigated the dilation pressure required to achieve complete expansion in the high-pressure group.

RESULTS

In total, 71 patients were enrolled and allocated to either the low-pressure group (n = 34) or the high-pressure group (n = 37). The 12-month patency rates showed no significant difference between the low- and high-pressure groups (47% and 49%, respectively; p = 0.87). In the low-pressure group, the patency rate was not different between patients with complete dilation and residual stenosis (44% and 50%, respectively; p = 0.87). The Cox proportional hazard model revealed that the 12-month patency rate was associated with the stenosis diameter (hazard ratio 0.36; p = 0.001) and the presence of diabetes (hazard ratio 0.33; p = 0.018). Finally, the pressure required to achieve complete dilation was ≤20 atm in 76% of patients and ≤30 atm in 97% of patients. One patient required a dilation pressure of >30 atm.

CONCLUSION

The patency rate does not differ between low-pressure dilation and high-pressure dilation.

Advances in Endovascular Techniques to Treat Failing and Failed Hemodialysis Access

During the decade since JEVT was inaugurated, we have witnessed the growing application of endovascular techniques for arteriovenous (AV) access in parallel with the evolution of endovascular therapy for arterial pathology. To date, few if any technologies have compared with balloon angioplasty for treating venous anastomotic stenosis, the most common cause of access failure. Only one device, which incorporates the principles of access graft design and self-expanding stent technology, has been uniquely conceived for this pathology. The encapsulated polytetrafluoroethylene stent-graft has achieved reasonable preliminary results, but randomized data is forthcoming. Technology to clear the clot from a thrombosed graft continues to evolve, but will never be as cost-effective as simple balloon thrombectomy. However, the pressure placed on providers to perform all percutaneous interventions and move away from open techniques continues to fuel interest in this component of treatment. Finally, the pursuit of a completely percutaneous AV access continues. As with endovascular procedures in general, whether or not the procedure is cost-effective or time-consuming seems to take a back seat to the all-percutaneous approach that so many seem to converge upon. Moreover, as most autogenous fistulas and AV grafts can be created with minimal incisions under local anesthesia, the pursuit of a completely percutaneous access system seems more like an academic exercise than a practical application of technology. We must try and avoid the tendency to “minimize invasiveness” with technology that is maximally intensive (and expensive), such as limiting ourselves to only percutaneous methods. Given the increasing pressure to have an all autogenous access program, current techniques that apply well in prosthetic grafts will need to be modified to accommodate the different biology of a native fistula. Clearly, the enlarging end-stage renal disease population will continue to provide endovascular specialists with clinically challenging problems requiring new and revolutionary technology.

Arteriovenous Access Failure, Stenosis, and Thrombosis

Vascular access–related complications can lead to patient morbidity and reduced patient quality of life. Some of the common arteriovenous access complications include failure to mature, stenosis formation, and thrombosis.

Outcomes of percutaneous interventions in transposed hemodialysis fistulas compared with nontransposed fistulas and grafts

PURPOSE

To compare postpercutaneous intervention outcomes of autogenous venous-transposition arteriovenous fistulas (AVFs) versus those of autogenous nontransposed AVFs (nAVFs) and prosthetic arteriovenous grafts (AVGs).

MATERIALS AND METHODS

A total of 591 hemodialysis accesses (195 transposed AVFs [tAVFs], 205 nAVFs, 191 AVGs) in 522 patients (278 male; mean age, 57 y; range, 15–91 y) underwent percutaneous transluminal angioplasty (PTA) and/or mechanical thrombectomy (ie, declotting). Access characteristics, surgical history, percutaneous interventions, postinterventional primary and secondary access patency, and follow-up data were collected. Cox proportional-hazards regression analyses, Fisher exact tests, and χ2 tests were performed.

RESULTS

Mean follow-up period was 32 months. Mean access ages at initial percutaneous intervention were 260 days (tAVF), 206 days (nAVF), and 176 days (AVG; P < .01). One-year postinterventional primary patency (PIPP) rates were 25% (tAVF), 24% (nAVF), and 14% (AVG). One-year postinterventional secondary patency (PISP) rates were 77% (tAVF), 61% (nAVF), and 63% (AVG). Median PIPP durations were 138 days (tAVF), 121 days (nAVF), and 79 days (AVG; P = .0001). Median PISP durations were 1,076 days (tAVF), 783 days (nAVF), and 750 days (AVG; P = .019). Total interventions needed to maintain PISP were 2.4 (tAVF), 1.3 (nAVF), and 3.2 (AVG) per patient-year (P < .001), which included 1.9, 1.2, and 1.4 PTAs (P < .01) and 0.45, 0.15, and 1.8 declotting procedures, respectively (P < .001).

CONCLUSIONS

Based on the number of percutaneous interventions needed to maintain PISP, these results confirm the current Dialysis Outcomes Quality Initiative access preference of nAVFs before tAVFs before AVGs. tAVFs offered superior postinterventional outcomes than AVGs. With additional interventions, tAVFs could even outperform nAVFs in terms of PISP.

Long-term preservation of native arteriovenous dialysis fistulas

Preservation of native arteriovenous fistulas (AVFs) in the long term can be technically challenging. Various anatomic or functional problems can occur and multiple open and/or endovascular interventions may be required for extended preservation of native accesses. In this report, we review vascular access maintenance in a 72-year-old woman during a 5-year period. Multiple complications of her native radiocephalic AVF included recurrent occlusions, a central venous stent fracture and symptomatic venous outflow stenosis. We present this case to illustrate the various techniques and combination of approaches used in the long-term preservation of a native AVF.

Angioplasty of Obstructed Homograft Conduits in the Right Ventricular Outflow Tract With Ultra-Noncompliant Balloons

Background—

Angioplasty and stent placement in right ventricle-to-pulmonary artery (RV-PA) conduits have been shown to prolong the functional lifespan of a conduit. Safety and efficacy of angioplasty of obstructed RV-PA homografts using ultra-noncompliant (UNC) or ultrahigh-pressure balloons are unknown.

Methods and Results—

From 2004 to 2012, 70 patients underwent 76 procedures for angioplasty of RV-PA homografts with UNC Atlas balloons. The UNC group was compared with a partially contemporaneous control cohort of 81 patients who underwent 84 angioplasty procedures with conventional balloons. Acute hemodynamic changes after angioplasty of homografts with UNC balloons included significantly reduced RV:Ao pressure ratio ( P =0.02) and right ventricular outflow tract gradients ( P ≤0.001). Balloon waist resolution was more frequently achieved with UNC balloons ( P =0.04), and balloon rupture occurred less often ( P <0.001). Conduit tears of any severity occurred in 22% of patients overall and were more common in the UNC group ( P =0.001). Patients with any conduit tear had significantly greater reduction in their RV:Ao pressure ratio ( P <0.001) and right ventricular outflow tract gradient ( P =0.004) than those with no tear. There were 4 unconfined tears, all in the UNC group, with no acute decompensations or deaths and only 1 patient who required surgical management.

Conclusions—

RV-PA conduit tears are common in patients undergoing angioplasty, but clinically important tears, which only occurred during UNC angioplasty in this series, were uncommon. UNC balloons can be used to good effect with significant reduction in right ventricular outflow tract gradient and the RV:Ao ratio when compared with conventional balloons.

Most important chronic complications of arteriovenous fistulas for hemodialysis

The aim of this review was to highlight the most important complications of arteriovenous fistulas (AVFs) for hemodialysis (HD). The quality of vascular access for HD should be suitable for repeated puncture and allow a high blood flow rate for high-efficiency dialysis with minimal complications. The dialysis staff must be well versed in manipulation of the AVF, and there should be a minimal need for corrective interventions. Construction of an AVF creates conditions for increasing the flow of blood through the venous system. Fulfillment of these conditions reduces the risk of turbulence and endothelium injury, which, in turn, minimizes the potential for stenosis. An AVF is closest to the ideal model of vascular access. The most important complications of fistulae for HD are lymphedema, infection, aneurysm, stenosis, congestive heart failure, steal syndrome, ischemic neuropathy and thrombosis. In HD patients, the most common cause of vascular access failure is neointimal hyperplasia. It is important to gain information about early clinical symptoms of AVF dysfunction in order to prevent and adequately treat potential complications.

Ultrahigh-Pressure Angioplasty versus the Peripheral Cutting Balloon™ for Treatment of Stenoses in Autogenous Fistulas: Comparison of Immediate Results

Purpose

To compare the immediate results of ultrahigh-pressure (UHP) balloons vs. peripheral cutting balloons (PCB) for the treatment of stenoses associated with autogenous fistulas using intra-access blood flow measurements.

Materials and Methods

This prospective randomized study consisted of 22 hemodialysis (HD) patients with autogenous fistulas who had decreased intra-access blood flow (<500 mL/min). All patients underwent a fistulogram and intraprocedural blood flow measurements. Patients were randomized once into two groups; one group undergoing UHP angioplasty and the second group undergoing PCB angioplasty. Randomization occurred once after the diagnostic fistulogram and each patient in each arm only underwent percutaneous transluminal angioplasty with either UHP or PCB. The study cohort consisted of 12 patients in the UHP group and 10 patients in the PCB group. Data collected included fistula anatomy, degree of stenosis, length of stenosis, balloon specifications and residual stenosis.

Results

The 22 study patients underwent 35 angioplasty procedures; 23 in the UHP group (12 patients) and 12 in the PCB group (10 patients). The technical success rate was 91%. The pre-intervention mean blood flow was 288 mL/min in the UHP group and 391 mL/min in the PCB group. The post-intervention mean blood flow was 613 mL/min in the UHP group and 606 mL/min in the PCB group. The mean increase in blood flow was 325.8 mL/min in the UHP group and 213 mL/min in the PCB group. This represents a relative mean increase in blood flow of 253% in the UHP group and 85% in the PCB group. An unpaired t-test showed there was no significant difference between the groups with respect to pre-flow, post-flow, and mean and relative mean increase in flow. There were two failures; one in the UHP group and one in the PCB group. There was one minor complication (2.8%) but no major complications.

Conclusions

In this small group of HD patients with autogenous fistulas our comparison of UHP to the PCB demonstrated that the immediate results, as determined by measurement of intra-access blood flow, were equivalent. Further long-term follow-up will be required to determine the longevity of these results

Incidence and management of percutaneous transluminal angioplasty-induced venous rupture in the "fistula first" era

PURPOSE

Percutaneous transluminal angioplasty (PTA)-induced venous rupture is a common complication of hemodialysis access interventions. The authors sought to determine if venous rupture rates and management differed between grafts and fistulas, and in the fistula subset, between transposed and nontransposed fistulas.

MATERIALS AND METHODS

Patients experiencing venous rupture during hemodialysis PTA over a 5-year period were identified. Of 1,985 hemodialysis interventions, 75 ruptures occurred in 69 patients (46 women) with a mean age of 63 years (range, 31-88 y). Rupture rates, proportion of successful treatments, and treatment type and number (ie, balloon tamponade, stent, covered stent) were determined.

RESULTS

Rupture was more common in fistulas overall (5.6%, 39 of 693) compared with grafts (2.8%, 36 of 1,292; P = .002), in transposed (10.7%, 20 of 187) compared with nontransposed fistulas (3.8%, 19 of 506; P = .001), and in transposed fistulas compared with grafts (P = .0001). There was no significant difference between nontransposed fistulas and grafts. Treatment success (ie, resolution of extravasation) was the same among groups: 69% (27 of 39) in fistulas overall, 70% (14 of 20) in transposed fistulas, 68% (13 of 19) in nontransposed fistulas, and 72% (26 of 36) in grafts. There was a greater need for stents in grafts (38.9%, 14 of 36) compared with fistulas (12.8%, five of 39; P = .003).

CONCLUSIONS

PTA-induced rupture is more common in fistulas than grafts, and this effect seems nearly entirely driven by transposed fistulas. Although rupture treatment in fistulas of all types yielded similar success to grafts, and graft ruptures were more difficult to treat than fistula ruptures, the high rupture rates in transposed fistulas attest to the increased difficulty of treating this subset of fistulas.

The role of stents in the treatment of congenital heart disease: Current status and future perspectives

Intravascular or intracardiac stenoses occur in many forms of congenital heart disease (CHD). Therefore, the implantation of stents has become an accepted interventional procedure for stenotic lesions in pediatric cardiology. Furthermore, stents are know to be used to exclude vessel aneurysm or to ensure patency of existing or newly created intracardiac communications. With the further refinement of the first generation of devices, a variety of "modern" stents with different design characteristics have evolved. Despite the tremendous technical improvement over the last 20 years, the "ideal stent" has not yet been developed. Therefore, the pediatric interventionalist has to decide which stent is suitable for each lesion. On this basis, currently available stents are discussed in regard to their advantages and disadvantages for common application in CHD. New concepts and designs developed to overcome some of the existing problems, like the failure of adaptation to somatic growth, are presented. Thus, in the future, biodegradable or growth stents might replace the currently used generation of stents. This might truly lead to widening indications for the use of stents in the treatment of CHD.

Ultra-high-pressure balloon angioplasty for treatment of resistant stenoses within or adjacent to previously implanted pulmonary arterial stents

BACKGROUND

Stents are essential tools in the management of pulmonary arterial (PA) stenosis in patients with congenital heart disease. Although stents can usually be reexpanded as children grow, resistant in-stent or peri-stent obstruction can complicate the management of PA stents. Angioplasty with ultra-high-pressure (UHP) balloons may facilitate successful treatment of stent-associated PA stenoses that are resistant to high-pressure dilation.

METHODS AND RESULTS

We reviewed patients who underwent UHP angioplasty of in-stent or peri-stent PA stenoses that were resistant to high-pressure redilation. A resistant stenosis was defined as a residual balloon waist during high-pressure redilation of the stent, along with a pressure gradient and/or angiographic stenosis. Thirty-four lesions in 29 patients, including 8 with multiple concentric, overlapping, or adjacent stents, were included. The median age at UHP angioplasty was 9 years, and a median of 4 years had elapsed since unsuccessful high-pressure angioplasty. Thirty-one of the 34 (91% [81% to 100%]) UHP angioplasty procedures were successful in relieving the resistant stenosis. Balloon:waist diameter ratios were conservative (median 1.26), reflecting the ability of UHP balloons to "fracture" nearly all obstructions. After UHP dilation, lesion diameter increased by a median of 3.1 mm (36%), significantly more than after previous high-pressure dilation (1.3 mm, 19%; P<0.001). In 5 lesions, UHP angioplasty fractured the stent, allowing further vessel expansion. There were no vascular or other complications.

CONCLUSIONS

UHP angioplasty was safe and effective for treatment of stent-related resistant PA stenosis in this series; the ability to fracture maximally expanded stents may extend the utility of stents in the pediatric population.

Primary Cutting Balloon Angioplasty for Treatment of Venous Stenoses in Native Hemodialysis Fistulas: Long-Term Results from Three Centers

AIM

To evaluate the technical success and patency rates following primary cutting balloon angioplasty for venous stenoses in native dialysis fistulas.

METHODS

Forty-one patients (26 men, 15 women; age range 26-82 years, average age 59 years) underwent 50 (repeat procedures in 9 patients) primary cutting balloon (PCB) angioplasty procedures in three institutions by three primary operators. The indication was primary stenosis in 21 patients, recurrent lesions in 15, and immature fistulas in 5. A PCB was used alone in 17 cases, but was followed by a larger standard balloon in 33 cases. Follow-up included ultrasound, flow analysis and urea reduction ratio, and ranged from 2 to 30 months (mean 14 months).

RESULTS

The technical success rate was 98%. All procedures were relatively painless. Two PCBs burst and 4 leaked, but without causing any morbidity. Nineteen fistulas were still working at last follow-up. Primary patency rates at 6, 12, and 24 months using Kaplan-Meier analysis were 88%, 73%, and 34%, respectively, and the primary assisted patencies were 90%, 75%, and 50%, respectively.

CONCLUSION

PCB angioplasty has high technical success and low complication rates. The long-term patency rates are favorable for PCB angioplasty and compare favorably with other series.

Ultrahigh-pressure versus High-pressure Angioplasty for Treatment of Venous Anastomotic Stenosis in Hemodialysis Grafts: Is There a Difference in Patency?

PURPOSE

Ultrahigh-pressure (UHP) balloon catheters were compared with high-pressure (HP) balloon catheters to determine if there was a difference in patency after percutaneous transluminal angioplasty (PTA) of venous anastomotic stenoses.

MATERIALS AND METHODS

A retrospective study was conducted from January 2001 to September 2005 that included 22 patients with synthetic hemodialysis grafts who underwent 110 PTA procedures for venous anastomotic stenoses. Data collected included graft configuration and location, percent stenosis, balloon type used, residual stenosis, and total access blood flow before and after intervention. Patency from time of initial PTA to the next intervention was estimated with the Kaplan-Meier technique, with initial failures included in the analysis.

RESULTS

A total of 55 PTAs were performed in each group. Technical success rate was 96% (n = 106) and clinical success rate was 100%. Median survival times were 4.6 months for the UHP cohort and 5.4 months for the HP group. When each event was considered independent, the difference was significant (P = .014). However, when each PTA event was considered dependent on earlier PTA events, no significant difference in patency was observed (P = .64). The mean increases in access blood flow rate by ultrasound dilution (available for 71 events) after PTA were 264 mL/min with UHP and 524 mL/min with HP (P = .14, Student t test). One minor complication (0.9%) of focal extravasation after PTA occurred and resolved with prolonged balloon inflation.

CONCLUSION

Routine use of UHP for PTA of venous anastomotic stenoses in synthetic hemodialysis grafts was not associated with any significant change in patency compared with routine HP balloon angioplasty.

Mechanism of dipyridamole's action in inhibition of venous and arterial smooth muscle cell proliferation

Dipyridamole is a potential pharmacological agent to prevent vascular stenosis because of its antiproliferative properties. The mechanisms by which dipyridamole inhibits the growth of vascular smooth muscle cells, especially venous smooth muscle cells, are unclear. In the present study, dipyridamole transiently but significantly increased cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) levels in human venous and arterial smooth muscle cells in a time- and dose-dependent manner. Peak concentrations of both cyclic nucleotides were achieved at 15-30 min. and correlated with inhibition of proliferation in both cell types. The antiproliferative effects of dipyridamole observed at 48 hr were similar whether drug exposure was only 15 min. or sustained for 48 hr. Specific competitive inhibitors of protein kinases A and G attenuated the antiproliferative effects of subsaturating concentrations of dipyridamole, with the effects of protein kinase inhibition being particularly pronounced in venous smooth muscle cells. Flow cytometry analysis showed that dipyridamole caused an enrichment of cells in G(0)/G(1) and a corresponding reduction of cells in S phase. These data indicate that a transient increase in cGMP and cAMP is sufficient to induce downstream kinase activation and subsequent cell cycle arrest, and that protein kinase G may be more important than protein kinase A in mediating the growth inhibitory effect of dipyridamole in venous protein kinase.

Salvage of nonmaturing native fistulas by using angioplasty

PURPOSE

To retrospectively review outcomes following angioplasty of nonmaturing autogenous hemodialysis fistulas.

MATERIALS AND METHODS

Institutional review board exemption was received for this HIPAA-compliant retrospective study; informed consent was waived. During 48 months, 101 patients underwent fistulography for percutaneous salvage of nonmaturing native fistulas. Clinical and technical success, need for secondary interventions, and complications were recorded according to consensus definitions. Patency following angioplasty was estimated with the Kaplan-Meier technique. Patient age, sex, ethnicity, fistula age, fistula type, number of stenoses, maximal angioplastic balloon diameter used, and presence of palpable thrill following angioplasty were examined as predictors of primary patency of the fistula following intervention by using Cox proportional hazards model.

RESULTS

Mean patient age was 58 years; 35% were women. Median time from fistula creation to fistulography was 2.5 months. Hemodynamically significant (>50%) stenoses were identified in 88% (89 of 101) of patients; angioplasty was attempted in 96% (85 of 89). Technical success was achieved in 92% (78 of 85) of fistulas following angioplasty; clinical success of normal hemodialysis with total access blood flow of more than 500 mL/min occurred following 88% (75 of 85) of angioplastic interventions. No major and two minor complications occurred. Mean primary unassisted patency at 3, 6, and 12 months was 60%+/-6% (95% confidence interval), 45%+/-6%, and 34%+/-6%, respectively. Additional angioplasty (n=12), stent placement (n=1), or thrombectomy (n=1) during subsequent interventions resulted in mean secondary patency at 3, 6, and 12 months of 82%+/-4%, 79%+/-5%, and 75%+/-6%, respectively. Patients without thrill following angioplasty were more than twice as likely to lose patency as patients with thrill (P=.035). No relationship was seen between primary patency and other predictors examined.

CONCLUSION

Early fistulography enables identification of underlying areas of stenosis in nonmaturing fistulas, which can be safely and effectively treated with angioplasty. With continued surveillance and repeat interventions, functional patency can be sustained in the majority of fistulas.

Percutaneous mural fenestration and angioplasty for the treatment of a refractory hemodialysis-related venous stenosis

Venous stenoses are the leading cause of dialysis graft and mature dialysis fistula malfunction. We report a simple, inexpensive technique for treating stenoses that are refractory to conventional balloon angioplasty and present a case in which this technique was successfully applied.

Cutting balloons for the treatment of vascular stenoses

The aim of this article is to review the mechanism, technical characteristics, biological response and clinical applications of cutting balloon angioplasty in peripheral vessels. The cutting balloon is a non-compliant, balloon catheter equipped with three-to-four microtome-sharp atherotomes. When used appropriately, it is safe and easy to use, with a high immediate success rate and few complications, provided oversizing is avoided. There is some evidence that pre-dilation with a standard or high-pressure balloon may also predispose to vascular rupture. The cutting balloon has proved to be beneficial in treating difficult complex lesions in the coronary arteries. Early experience in non-coronary vessels shows that cutting balloon angioplasty can be used to treat peripheral bypass anastomotic and haemodialysis fistula stenoses that are resistant to conventional high-inflation pressures. Its application in de novo peripheral arterial lesions and non-coronary in-stent restenosis is still under discussion. Theoretically, this device induces a smaller degree of vessel wall injury localised to the area of incisions and sparing the interincisional segments; however, this postulated reduction in restenosis rates has not been confirmed in clinical practice.

Angioplasty Balloon Inflation Pressures during Treatment of Hemodialysis Graft–related Stenoses

PURPOSE

This two-part prospective investigation was designed to determine the balloon inflation pressures required to dilate stenoses associated with hemodialysis grafts and evaluate the burst pressures of five different angioplasty balloons.

MATERIALS AND METHODS

Eighty-nine patients with dysfunctional hemodialysis grafts were enrolled and underwent fistulography. The diagnostic studies revealed 104 stenoses, which were treated with balloon angioplasty. The characteristics of these stenoses and the balloon inflation pressures required to dilate the lesions were recorded. In part two of this investigation, the burst pressures of five different angioplasty balloons were evaluated immediately after their use during angioplasty procedures. Twenty-five balloons of each type were inflated until the balloon burst or 30 atm of pressure was achieved. Several different statistical tests were used to analyze the data set.

RESULTS

The mean balloon inflation pressure required to dilate all 104 stenoses was 17.2 atm. Subgroup analysis revealed that the mean balloon inflation pressure required to dilate 75 venous anastomotic stenoses was 17.9 atm and that a mean pressure of 15.6 atm was required to dilate 29 stenoses located within the native outflow veins. The angioplasty balloon burst pressure experiments revealed that the majority of the tested balloons can be inflated to pressures 5-6 atm greater than the manufacturers' rated burst pressures. However, the margin of safety for overinflation was variable among the balloons tested, and angioplasty balloons experience fatigue with repeated inflations.

CONCLUSION

The majority of stenoses associated with hemodialysis grafts can be successfully dilated with use of available high-pressure angioplasty balloons.

Prospective Study of Balloon Inflation Pressures and Other Technical Aspects of Hemodialysis Access Angioplasty

PURPOSE

Balloon angioplasty is a mainstay in the treatment of failing or thrombosed hemodialysis access grafts and fistulas. A sizable body of outcomes data exists concerning percutaneous transluminal angioplasty (PTA) in hemodialysis access, yet there is a relative paucity of technical information available, especially regarding dilation pressures. The aim of the present study was to compile such information, which can be critical to the choice of devices for PTA and to the design of future clinical trials seeking to improve outcomes in this area.

MATERIALS AND METHODS

Technical data were collected prospectively for 102 PTA procedures (66 prophylactic PTA procedures and 36 PTA procedures performed during access thrombectomy). Demographic data concerning the access were collected. Technical data were collected individually for each lesion treated, including lesion location; degree of stenosis (in quartiles); lesion length; PTA balloon brand, size, and length; pressure at which the waist of the balloon was effaced; residual stenosis; and reason for additional balloons or inflations if used. Outcomes data other than residual stenosis were not collected, but the endpoint for all interventions was a thrill in the access.

RESULTS

A total of 230 lesions were treated. Two (1%) could not be successfully treated with PTA despite the use of "ultra high" pressure (approximately 40 atm); one was treated successfully with parallel wire technique and the other was revised surgically after the use of a cutting balloon also failed. Overall, 55% of lesions required pressures greater than 15 atm to efface the waist. Excluding initial failures, 20% of lesions in native fistulas and 9% in grafts required very high pressure (>20 atm) to efface the waist (P = .02). High pressure was needed less frequently in PTA procedures performed in the setting of thrombectomy procedures than in prophylactic PTA procedures (P = .0001). Residual stenosis was positively correlated with severity of initial stenosis and negatively correlated with duration of inflation.

CONCLUSIONS

Conventional angioplasty balloons are inadequate for the treatment of most hemodialysis access stenoses. High pressures (>15 atm) are commonly needed for PTA in hemodialysis access. Very high pressures (>20 atm) are more frequently needed in native fistulas.

Use of the Peripheral Cutting Balloon to Treat Hemodialysis-related Stenoses

PURPOSE

To compare the effectiveness and safety of use of the peripheral cutting balloon (PCB) versus standard percutaneous transluminal angioplasty (PTA) for the treatment of hemodialysis-related stenoses.

MATERIALS AND METHODS

This prospective, randomized multicenter clinical trial included 340 patients with stenotic or thrombosed hemodialysis grafts who were randomized to receive treatment with the PCB or PTA for venous outflow stenosis. One hundred seventy-three patients underwent treatment with the PCB, 101 with stenotic grafts and 72 with thrombosed grafts. PTA was used to treat 167 patients, 94 patients with stenotic grafts and 73 with thrombosed grafts. The follow-up period extended for 6 months.

RESULTS

The procedural success rates were 80.8% and 75.4% for the PCB and PTA groups, respectively (P = .24). With use of the PCB, the primary patency rates of the target lesions were 84.3%, 65.8%, and 47.9% at 1 month, 3 months, and 6 months, respectively. With PTA, the primary patency rates of the target lesions were 77.7%, 63.4%, and 40.5% at 1 month, 3 months, and 6 months, respectively. The primary patency rates of the entire vascular access circuit were 82.6%, 61.0%, and 43.3% at 1 month, 3 months, and 6 months, respectively, with use of the PCB. For patients who were treated with PTA, the primary patency rates of the vascular access circuit were 75.9%, 61.0%, and 36.3% at 1 month, 3 months, and 6 months, respectively. When comparing the PCB and PTA, there was no difference in the 6-month primary patency rates in the target lesion (P = .373) or the entire vascular access circuit (P = .531). There were nine device-related complications in the PCB group (5.2%): five venous ruptures (2.9%), three venous dissections (1.7%), and one case of thrombosis (0.6%). There were no device-related complications in the PTA group.

CONCLUSION

This prospective, randomized trial comparing use of the PCB versus standard PTA for treatment of hemodialysis-related venous stenoses demonstrated that the PCB provides equivalent 6-month patency to PTA for stenotic and thrombosed grafts.

Mechanical Thrombectomy of Hemodialysis Fistulae and Grafts

In this article, the authors present approaches they use in performing dialysis access intervention-in particular clotted access. It is not meant to be a comprehensive review of dialysis access management. At our institution, mechanical thrombectomy is the primary mode of treatment for clotted hemodialysis access. We will present physical examination findings in clotted dialysis access and contraindications for mechanical thrombectomy in dialysis access. We will also discuss the devices for mechanical thrombectomy and the techniques we use. Finally, we will discuss the difficulties encountered in these procedures and their solutions.