Version May 2024
INTRODUCTION — Treatment of clinically significant stenosis associated with hemodialysis arteriovenous (AV) access is recommended to prevent AV access failure [1]. The goal of intervention is to restore and maintain access function for as long as possible with the fewest interventions. The consequences of AV access failure to a patient relying on hemodialysis include missed or inadequate dialysis treatments and the risks associated with hospitalization and catheter usage. These adversely affect the patient's quality of life and contribute substantially to increasing health care costs.
Percutaneous angioplasty of hemodialysis AV access stenosis is safe, effective, and easily performed [2-8]. Lesions in all locations associated with the AV can be effectively and safely treated with minimal discomfort [2]. Compared with surgical revision, percutaneous angioplasty has the principal advantage of preserving potential venous access sites, and following treatment, the AV access is immediately available for hemodialysis.
Techniques for percutaneous angioplasty of AV hemodialysis access are reviewed here. Definitions for the hemodialysis access time points used in this topic (eg, primary patency, assisted primary patency, postintervention patency) are provided in the figure (figure 1 and table 1).
Issues related to monitoring and diagnosis of stenosis of chronic hemodialysis AV access, and indications for intervention are discussed in detail separately. (See "Clinical monitoring and surveillance of the mature hemodialysis arteriovenous fistula" and "Clinical monitoring and surveillance of hemodialysis arteriovenous grafts to prevent thrombosis" and "Endovascular intervention for the treatment of stenosis in the arteriovenous access".)
PATIENT EVALUATION — In most instances, the patient has been referred to the treatment facility because of an abnormality that was detected at the dialysis clinic. Such abnormalities may include:
●Problems noted by physical examination (see "Early evaluation of the newly created hemodialysis arteriovenous fistula" and "Physical examination of the mature hemodialysis arteriovenous fistula" and "Physical examination of the arteriovenous graft")
•Hyperpulsatility of the access
•Abnormal thrill – decreased, loss of diastolic component
•Localized thrill along course of draining vein (site of stenosis)
•Abnormal bruit – high-pitched, loss of diastolic component
•Failure of fistula to collapse when arm is elevated above level of heart
•Development of aneurysms or signs of distal ischemia
●Problems noted during dialysis treatment (see "Clinical monitoring and surveillance of the mature hemodialysis arteriovenous fistula" and "Clinical monitoring and surveillance of hemodialysis arteriovenous grafts to prevent thrombosis")
•Persistently increased venous pressure
•Inability to achieve target dialysis blood flow rate or progressive increase in the prepump absolute pressure to achieve desired dialyzer blood flow
•Unexplained decrease in the delivered dialysis dose (Kt/V)
•Prolonged bleeding post needle removal, persistent
•Evidence of recirculation
•Thrombosis of access
The preprocedure evaluation should begin with a general history and physical examination that includes a detailed examination of the access arm and AV access. Although not particularly good for identifying central lesions, in most cases, if a significant problem is present, it can be identified by physical examination. Ultrasound examination should be included in the examination and improves the sensitivity of recognizing a significant lesion [9].
The preprocedure examination is important for several reasons:
●It is important to have reasonable assurance of the presence of a treatable lesion prior to proceeding with angiography. It is not unusual for a patient to be referred who does not have a problem that warrants intervention.
●It will help plan the approach to intervention.
●It provides the interventionalist with a baseline for comparison postprocedure.
●It is necessary for identifying any contraindications to the procedure.
Determining access blood flow (Qa) using duplex ultrasound should be part of the preprocedure examination [1]. Based upon this assessment, a determination can be made whether a flow reduction procedure might be appropriate. Brachial artery flow should be used when measuring Qa, with imaging performed at least 5 cm proximal to the anastomosis [10-12]. Because a high brachial artery bifurcation is present in 12 to 19 percent of patients, care must be taken to assure that the measurement is being made from the brachial artery [13,14]. (See "High-flow hemodialysis arteriovenous access", section on 'Access flow measurement' and "High-flow hemodialysis arteriovenous access", section on 'Flow reduction'.)
LESION CONFIRMATION AND SELECTION
Cannulating the access — Cannulation of the AV access proceeds like needle placement prior to dialysis using the site selected in the preprocedure examination. Local anesthesia is generally all that is needed to gain access to the fistula or graft; however, because balloon angioplasty of stenotic lesions in the native vessels is potentially very painful, adequate sedation and local anesthesia at the site of the lesion should be provided. The patient should be monitored for discomfort and the dosage titrated as needed since the requirement for adequate sedation varies from patient to patient. All patients require hemodynamic monitoring, and supplemental nasal oxygen should also be provided. (See "Procedural sedation in adults in the emergency department: General considerations, preparation, monitoring, and mitigating complications".)
To aid cannulation, manual compression or using a sterile tourniquet above the cannulation site helps engorge the veins. In general, an AV fistula is somewhat more difficult to cannulate than an AV graft. The AV fistula is more easily compressed, and more caution is needed to avoid passing the needle through the back wall of the vessel. In addition, a dysfunctional AV fistula, particularly one that has failed to mature, is difficult to palpate. For these reasons, a micropuncture (21 gauge) needle is preferred. However, a standard (18 gauge) introducer needle is adequate and works well for accessing a mature AV fistula or an AV graft. When cannulation is problematic, ultrasound-guided cannulation can be very helpful. (See "Basic principles of ultrasound-guided venous access".)
Several considerations need to be taken into account during selection of the access site. These include:
●The needle must be directed toward the stenotic lesion (either antegrade or retrograde). The preprocedure examination should identify the most likely location of the stenosis. Some AV accesses will have more than one lesion. (See 'Patient evaluation' above.)
●The access insertion site should lie in a straight line with the suspected lesion to facilitate placement of the balloon catheter unless the distance from the access site to the lesion is relatively short (ie, several centimeters). Passing the catheter tip through the stenosis when there is resistance will be more difficult if the catheter needs to negotiate a curve.
●The distance between the access site and the suspected lesion needs to be long enough to accommodate the placement of an intravascular sheath through which the intravascular devices (eg, balloon, stent) are usually passed.
●If large aneurysms or pseudoaneurysms are present and the target lesion lies beyond them, it may be advantageous to cannulate away from these areas to avoid the problems of passing a guidewire through them.
Once an introducer needle has been placed, a guidewire is inserted over which an intravascular sheath is placed. An intravascular sheath should always be used to maintain the access site and for the administration of intravenous radiocontrast media and medications, as needed. The size of the sheath is determined by the anticipated diameter of the angioplasty balloon that will be used. The required minimal sheath size for each balloon catheter is specified by the manufacturer on the label.
In some cases, such as what occurs with juxta-anastomotic stenosis, it is extremely difficult to cannulate the access at the optimal site for treatment of the lesion. In these cases, it is necessary to cannulate the access in a retrograde direction to insert a sheath and treat the lesion adjacent to and at times involving the anastomosis because the vein is poorly developed downstream from the lesion. A technique referred to as balloon-guidewire entrapment (image 1) can be used to facilitate the process [15]. This technique requires that the access is first cannulated at a site that will allow a guidewire to pass in the direction of the desired treatment cannulation site. This is generally easily accomplished near the anastomosis. Once this initial site is cannulated, a sheath is inserted followed by a guidewire, which is advanced beyond the selected site for the treatment procedure. The angioplasty balloon is then inserted and advanced up to the selected site to use as a target. The balloon is inflated and cannulated with a micropuncture needle. Needle entry into the balloon is indicated by clear liquid exiting the needle hub. At this point, the microguidewire is inserted into the balloon. Once the needle is removed, the balloon with the contained guidewire is retracted into the access. When the guidewire is well within the access, it can be held stationary while the balloon is totally extracted. At this point, the insertion of the microdilator can occur and the procedure can be continued.
Pretreatment angiogram — An angiogram should be performed to evaluate the anatomy of the AV access and its draining veins prior to treatment of any specific lesion. It is important to evaluate the entire access circuit through to the superior vena cava since multiple lesions are often present, both with AV fistulas and AV grafts [2,7,16-19]. All lesions should be documented for reference. It is also important to evaluate the arterial anastomosis and adjacent feeding artery. A retrograde arteriogram is accomplished by injecting contrast while manually occluding the access downstream (ie, in the direction of flow) from the injection site unless thrombus is present. Any evaluation of the arterial circulation prior to or following thrombectomy should be performed using a catheter to minimize the risk of arterial embolism.
Direct observation is necessary to perform AV access interventions. Although ultrasound-guided procedures have been reported [20-22], fluoroscopy with digital subtraction capability has advantages of identifying the location and extent of pathology, positioning of devices (eg, wires, balloon, stents), and for the management of any complications.
Systemic anticoagulation (eg, unfractionated heparin) is unnecessary because of the high blood flow rate in the dialysis access. During angioplasty, flow is occluded only for short intermittent periods, and clotting of a patent AV access during intervention rarely occurs. However, with treatment of a thrombosed hemodialysis AV access, we provide a bolus 5000 units of intravenous unfractionated heparin (or an alternative agent) to prevent rethrombosis. Anticoagulation may also be needed when multiple lesions will be treated and it is anticipated that the access will be occluded for more than a short interval, or when severe widespread venous spasm occurs.
Hemodialysis access angiography is usually accomplished using a nonionic iodinated radiocontrast agent that has been diluted 50:50 (table 2). The volume of radiocontrast needed for the entire angioplasty procedure is generally less than 50 mL. For patients with radiocontrast allergy, premedication may be needed, or an alternative agent can be used (eg, carbon dioxide [23]). If carbon dioxide is used, it should be injected into the venous limb of the AV fistula or AV graft, or at the arterial anastomosis to prevent reflux of gas into the proximal arteries [24]. Pulmonary hypertension and chronic obstructive pulmonary disease represent relative contraindications to the intravenous use of carbon dioxide.
Allergy to radiocontrast media and premedication regimens are reviewed separately. (See "Allergy evaluation of immediate hypersensitivity reactions to radiocontrast media" and "Radiocontrast hypersensitivity: Nonimmediate (delayed) reactions" and "Patient evaluation prior to oral or iodinated intravenous contrast for computed tomography", section on 'Premedication regimens'.)
Characterizing the lesion — Considerable variability is seen in the character of venous stenosis relating to location, length, severity of stenosis, and number of stenotic sites. (See "Endovascular intervention for the treatment of stenosis in the arteriovenous access", section on 'Sites of stenotic lesions'.)
There is nothing to suggest that angioplasty should be avoided for any specific type of lesion. In one review, the duration of unassisted patency for each category of lesion studied was statistically comparable to that of the entire group [2]. No significant differences were seen for length of lesion, multiple lesions, or location of the lesion. Although severity of the stenosis was not specifically evaluated in this study, it has not proven to be a factor for determining the success of angioplasty.
Measurement of stenosis — The percent stenosis is determined by comparing the lesion with the adjacent "normal" vessel (image 2). Measurement of the degree of stenosis is generally not a problem for an AV graft; however, identifying adjacent "normal" vessel diameter for an AV fistula or peripheral or central venous lesion can be challenging [2,7,25]. The vein can vary considerably in diameter along its length, and segments may be aneurysmal [26,27].
●Arterial anastomosis of AV fistula – The size of the arterial anastomosis of an AV fistula depends upon its construction, which may vary from surgeon to surgeon, but it is generally smaller than the adjacent artery. In addition, there is always a drop in pressure across the arterial anastomosis. Stenosis at this site should be defined by comparing the diameter of the anastomosis with the adjacent normal artery [28]. If the difference is 50 percent or greater, the anastomosis should be classified as stenotic.
●Venous anastomosis of AV graft – At the venous anastomosis of an AV graft, there is often a significant diameter discrepancy between the graft and the adjacent "normal" vein, such that in this instance, the comparison used for the diagnosis of anastomotic stenosis should be the graft.
Pseudostenosis — Not all lesions that look like a stenosis are a stenosis. Venous spasm is probably the most common cause of "pseudostenosis," but external compression can also cause confusion.
●Venous spasm – Venous spasm is relatively common. At times, simply passing a guidewire can precipitate spasm. It may be localized, or it may be more generalized. Spasm can easily be confused for a stenotic lesion if one is not careful. When a vein is first examined fluoroscopically, it is important to note the location, appearance, and extent of all lesions that are present. After angioplasty, if a new lesion has appeared, it is a vessel spasm (image 3). Attempts at dilatation may worsen the spasm and expose normal vein to the potential for endothelial damage in response to the pressure of the angioplasty balloon.
●External compression – There are a variety of ways that extrinsic pressure can give rise to the appearance of stenosis. In patients with an ectatic aorta, the left brachiocephalic vein can be compressed by the aortic arch (image 4) or by aortic arch branches. Extrinsic compression of the left brachiocephalic vein from an ectatic aorta can result in elevated venous pressure, and collateral veins can develop [29]. In very muscular hemodialysis patients, a muscle imprint can lead to an erroneous suspicion of stenosis of the axillary vein when the arm is adducted [30]. In very thin (cachectic) patients, the cephalic vein as it crosses the shoulder with the patient lying flat may look stenotic due to compression. A large breast or even a tight drape can also cause confusion at times. These latter situations do not usually have any hemodynamic consequence.
Treatment criteria
Recommendations — In evaluating access dysfunction, multiple areas of vessel narrowing may be seen on angiography. The question frequently arises as to which of these should be treated. The National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI) Practice Guidelines state that to qualify for treatment, a stenotic lesion should cause a greater than 50 percent decrease in the luminal diameter and be associated with clinical/physiological abnormalities (ie, the combination of which is defined as a "critical stenosis") [1,31]. (See 'Definition of critical stenosis' below.)
It should be emphasized that the key indication for treatment of stenosis is the presence of pathophysiology, not simply abnormal anatomy. In fact, there is evidence that the treatment of anatomic lesions without pathophysiology may be detrimental [32]. For central venous stenosis, this was illustrated in a retrospective study of 35 patients that compared the natural history of high-grade (>50 percent) asymptomatic central venous stenosis and the outcome of treatment with percutaneous transluminal angioplasty [32]. No untreated lesion progressed to symptoms, stent placement, or additional stenosis, whereas 8 percent of treated cases developed stenosis or symptom escalation.
Angioplasty of a hemodynamically significant stenosis associated with a dysfunctional, but not thrombosed, AV access can maintain functionality and delay thrombosis, but there is no convincing evidence that treatment of an asymptomatic anatomic stenosis, even if there is greater than 50 percent narrowing, has any beneficial effect [33-36]. We do not treat anatomic stenosis (>50 percent diameter reduction) that is not associated with a hemodynamic, functional, or clinical abnormality. Asymptomatic lesions are best managed by observation [32].
Definition of critical stenosis — A "critical stenosis" is the result of anatomic and pathophysiologic factors due to an inflow-outflow imbalance. The flow rate (ie, Qa) across a lesion can be normal, low, or high. A concern often prompting the treatment of venous stenosis is that the lesion will decrease Qa, eventually leading to thrombosis of the AV access. However, the correlation between the percent stenosis and a clinically significant decrease in Qa is low. While a 50 percent decrease in luminal diameter in a 6 mm vein may produce a marked decrease in Qa, a 50 percent decrease in luminal diameter for a 14 mm vein may be associated with an abnormally high Qa.
Thus, "critical stenosis" must be defined in functional terms and not based on lesion geometry alone, and what may be considered "critical" depends upon hemodynamics associated with the lesion [37,38]. A stenotic lesion has a clinical effect because of its impact on Qa; if Qa is not reduced, then the clinical problem relates to excessive inflow (which should be reduced) rather than restricted outflow. The parameter that exerts a restrictive effect on Qa and adversely affects the hemodynamics of the access is the absolute minimal luminal diameter (MLD) of the lesion [26,27]. This is especially true when dealing with central venous lesions in which the increased pressure resulting from a stenotic lesion can result in a markedly enlarged vein. While it may be impractical to measure MLD routinely, recognition of this principle is important. Dilating a venous segment to match an adjacent 12 to 14 cm vein is unnecessary and cannot be justified.
It should also be realized that the effect of multiple lesions that are less than 50 percent stenosis can be additive. If the flow rate is low, the additive effect of lesions may justify treatment, each of which individually would not warrant treatment. Clinical judgment is required in these cases.
Recurrent stenosis — Although venous stenosis tends to recur, repeat treatment is usually successful. However, if a lesion is recurring at a frequent interval, elasticity of the lesion is often the cause, and an alternative to what has been previously done, such as placement of a stent-graft or surgical correction, should be considered. The definition of "recurring at a frequent interval" is not well defined, and individualization of treatment is important. However, is it a general rule that if a lesion is recurring more than two times within three months, surgical therapy should be considered [1]. Prior to further treatment, it is important to consider whether prior angioplasty results were suboptimal and whether there might be a reasonable endovascular alternative to what has been previously tried.
ANGIOPLASTY TECHNIQUE — Treatment of venous stenosis using angioplasty is based upon observational studies that support the effectiveness of prospective monitoring and treatment of stenotic lesions for decreasing the incidence of AV access thrombosis and extending survival of the AV access (image 5).
Once intravascular access has been achieved and lesions have been identified on angiography, a guidewire is then passed through the sheath and advanced to the level of the central veins. Because an angioplasty balloon is relatively stiff, it should never be advanced without a guidewire; otherwise, serious damage to the vessel can occur. If the guidewire cannot be passed through the lesion, angioplasty cannot be performed. There is variability among different operators with respect to guidewire preference. But it is important that the guidewire size match the requirements for the devices that will be used. A 0.035 inch guidewire is adequate to start with for most cases. Guidewire manipulation may be needed in cases where the vein is tortuous. At times, a specialized guidewire may be required, or, alternatively, a guiding catheter can be used to assist passage of the guidewire.
Once the guidewire is in place, the angioplasty balloon catheter can be advanced to the most central lesion. If additional lesions are present, they are sequentially treated by moving peripherally in the extremity. Going from central to peripheral in the treatment of multiple lesions is important to ensure that the outflow from the lesion being treated is open. If it is not, the incidence of complications (vein rupture) may be increased, and such a complication, if it occurs, will be made worse if increased pressure is generated by downstream resistance.
Angioplasty balloons — The important information needed to make a proper balloon choice is provided on the catheter label. The coaxial angioplasty balloon catheter has two lumens. One is used as the passageway for the guidewire and the other is used to inflate the balloon. Desirable features for an angioplasty balloon are maintenance of the designed shape at high pressure (low compliance), ability to track over guidewire and to cross a tight lesion (low profile and crossability), and rupture resistance (strength).
●All standard angioplasty balloons are noncompliant; compliance is not a desirable feature for an angioplasty balloon. The angioplasty balloon is inflated with fluid, and its chamber will expand to a predetermined size and little more (less than 5 percent). Rather than continuing to expand with increasing pressure, it becomes firmer, exerting greater force while still retaining its shape and configuration, unless it ruptures. Although rupture of an angioplasty balloon from excessive pressure should not create a problem, rupture should be avoided.
●A small-profile balloon catheter permits the use of a smaller-diameter sheath to accommodate passage, resulting in a smaller defect in the vessel wall and skin. The size of sheath for a particular balloon is listed as "recommended introducer" on the angioplasty balloon catheter label. Once an angioplasty balloon has been inflated, it does not return to its former pre-use profile. For this reason, an angioplasty balloon should not be pre-expanded before initial use. If a balloon will be reused, it should be resized before it is reintroduced into the sheath. This is done by forcing the balloon cover back over the balloon to compress it to a smaller profile. Some manufacturers provide a short cylinder with flared ends located on the balloon shaft for this purpose. Resizing does not return the balloon to its original size, but it does reduce it considerably.
●Rupture resistance is an important feature of angioplasty balloons. All balloons have a pressure rating listed on the package, stated as rated burst pressure in atmospheres (atm), which is the pressure at or below which the manufacturer has a 95 percent level of confidence that the balloon will not rupture with a single inflation, 99.9 percent of the time. Exceeding this pressure is not recommended; however, there is actually some safety margin in this stated value. One study evaluated five different angioplasty balloon brands and found that with all types, overinflation by 5 to 6 atm could be safely accomplished without rupture [39]. Most operators do not hesitate to apply pressures of 20 atmospheres to a balloon rated at 16.
Type — Several types of specialty angioplasty balloons are available, including high pressure, ultra-high pressure, cutting, and drug coated.
●High-pressure balloons – The typical angioplasty balloons used for treating dialysis vascular access stenosis are referred to as high-pressure balloons. Low-pressure balloons, typically made of latex or silicone, are used primarily for clot extraction and occlusion (eg, the Fogarty catheter is a low-pressure balloon). High-pressure balloons have a pressure rating ranging from 16 to 20 atm.
●Ultra-high-pressure balloons – Ultra-high-pressure balloons have a manufacturer's burst-pressure rating in the range of 30 atm. Although more expensive than standard balloon catheters, these higher-rated balloons are very useful for extremely resistant venous lesions. Although not rated as such, ultra-high-pressure balloons can often be used successfully up to pressures of 40 atm.
●Cutting balloons – The cutting balloon is a special angioplasty balloon that has three or four sharp blades called atherotomes that are longitudinally bonded to its surface. These are microsurgical blades that are sharper than conventional surgical blades. The atherotomes expand radially with balloon inflation, incising the lesion. Cutting balloon angioplasty has been used as a primary treatment of stenotic lesions to reduce vascular trauma by producing a more controlled wall incision rather than an irregular tear, and as a secondary treatment of lesions that are resistant to standard angioplasty [40-43]. Few randomized trials have evaluated cutting balloon angioplasty for the treatment of hemodialysis AV access. Most data are from small, observational studies. Technical success is overall high, generally reported up to the range of 100 percent. Six-month primary patency rates range from 76 to 92 percent. Extravasation is the main complication, but the incidence is low. The available trials suggest there may be a benefit for primary treatment of lesions occurring at the graft-to-vein anastomosis [28,44,45]. However, its value at other sites is questionable. There is some evidence to support cutting balloon angioplasty as a treatment for resistant lesions, but larger studies are needed. In addition, less costly alternatives are available.
●Drug-coated balloons – Angioplasty balloons have been coated with a variety of drugs (eg, paclitaxel) with the aim of inhibiting neointimal hyperplasia. Outcomes from randomized trials comparing drug-coated balloons (DCBs) with standard angioplasty balloons for the treatment of venous stenotic lesions have generally supported longer-lasting results from DCBs [46-53]. One large trial did not show clear superiority of DCBs [53], whereas another reported improved primary patency in the DCB group (59.5 versus 18.2 percent) at six months [47].
Diameter and length — Angioplasty balloons are available in a wide variety of sizes, which are registered as diameter measured in millimeters and length measured in centimeters (eg, an 8 x 4 balloon would be 8 mm in diameter and 4 cm in length). The balloon diameter is measured fully inflated. The length of the balloon is the distance between the two radiopaque markers that are within the balloon. The balloon is actually slightly longer than its stated length because of its tapered shoulders. This portion of the balloon does not participate appreciably in its therapeutic function because of its reduced diameter.
When performing venous angioplasty, it is recommended that the balloon diameter exceed the diameter of the vessel by 10 to 15 percent (1 to 2 mm) [54]. By contrast, with arterial angioplasty, the balloon diameter should match the diameter of the artery. Individualization of the balloon size for each lesion is necessary to avoid undertreatment from too small a balloon or the increased risk of complications from a balloon that is sized too large.
There are several factors to consider in selecting a balloon catheter length. First, the relationship between the catheter and the guidewire is important. When passing a catheter over the guidewire, the back end of the guidewire must extend beyond the back end of the catheter and still have enough length within the vessel to maintain the access. This is also critical when difficulty has been encountered with the passing of a guidewire across a centrally located lesion. If it is necessary to pull the guidewire back so far that position is lost in order to insert the catheter, it can be problematic. Second, the catheter must be long enough to reach central venous lesions. Third, even though length is important, one does not want to have to use a guidewire that is so long that it is cumbersome. The standard guidewire length used in procedures performed on dialysis access is 145 to 150 cm. A catheter length of 75 cm appears to be optimal. This is long enough to reach the right atrium from a wrist insertion site in most patients.
Balloon inflation
Inflation devices — Balloon inflation can be accomplished with a saline-filled syringe or an inflation (insufflation) device (picture 1).
●Balloon dilation using a syringe works quite well, is economical, and is generally quicker than using an inflation device [55]. An acrylic syringe with a high-pressure stopcock is required; an ordinary syringe will not work for this purpose, and neither will a standard three-way stopcock, as these will not hold sufficient pressure. The pressure generated by a syringe is related to the ratio of the diameter of the plunger to the diameter of the orifice of the syringe. Thus, the smaller the syringe diameter, the greater the pressure that will be applied; 20, 10, and 3 cc syringes will generate approximately 10, 20, and 30 atm of pressure, respectively [55]. Some interventionalists prefer to use a syringe for inflating an angioplasty balloon because it gives them a better "feel" when trying to dilate a difficult lesion. We recommend using a syringe filled with dilute radiocontrast connected to a three-way stopcock, with a 10 cc syringe connected inline with the catheter and a 3 cc syringe connected to the side port. In this manner, the volume of the 10 cc syringe can be used to fill the balloon, and the 3 cc syringe can be used to apply pressure to achieve the balloon dilation. Radiocontrast is necessary in order for the balloon to be visible under fluoroscopy. This must be diluted for ease of injection and withdrawal so that it is not too viscous.
●A variety of commercial inflation devices are available, and all have the general appearance of a modified syringe (some are). The barrel is graduated in the same manner as a syringe. It has a Luer lock tip to which tubing and a three-way stopcock are attached to provide a connection to the balloon catheter. A pressure manometer, which registers the pressure measurement in atmospheres, is built into the side of the barrel.
Dilation pressure — Given that the lesion being treated has been determined to be pathophysiologically significant, the goal should always be to restore normal physiology through elimination of the lesion. This will require complete effacement of the lesion (image 6). Some type of anatomic disruption, such as a break or tear in the vessel, generally accompanies a successful angioplasty. If only stretching occurs, the likelihood of elastic recoil is high, and the angioplasty result will be inadequate [56].
The pressure required to dilate a particular lesion varies. In one study involving 230 stenotic lesions in AV grafts or AV fistulas, the pressure required to treat the lesion ranged from 10 to 20 atm in the majority of cases [54]. In 59 percent, the required pressure was >15 atm, and 20 percent of AV fistula lesions and 9 percent of AV graft lesions required a pressure >20 atm. The standard angioplasty balloon will generally tolerate more pressure than its stated burst pressure. How much more pressure it will tolerate varies for different manufacturers and even for different balloons from the same manufacturer. If the balloon's tolerance is exceeded, the balloon will rupture, and although this generally does not cause a problem, there is the potential for losing a portion of the balloon and, rarely, for damaging the vessel. For this reason, efforts should be made to avoid balloon rupture.
Typically, treatment is first attempted with a high-pressure balloon. If the lesion cannot be dilated without exceeding the burst pressure for the balloon, one should switch to an ultra-high-pressure balloon, the use of which has markedly reduced the incidence of "resistant" lesions. In one study of 87 patients with venous stenosis treated with standard high-pressure balloons, seven cases (8 percent) were resistant to dilatation. Using the ultra-high-pressure design, 100 percent success was obtained in these cases [57]. Venous angioplasty may be more effective if the vessel is over dilated by 20 to 30 percent. If total balloon effacement was observed, but recoil is observed following dilation, it is possible that a larger balloon might result in the type of anatomic disruption that would provide success; however, there is an increased risk of venous rupture with a larger balloon. This risk must be weighed against the fact that if the lesion cannot be successfully resolved, either with angioplasty or angioplasty plus stenting, surgical revision will be required.
Some lesion locations are notorious for being resistant to dilation (eg, the cephalic arch, the venous anastomosis of an AV graft) and will often require high-pressure balloons. In a study of 230 lesions, 55 percent required balloon inflation pressures greater than 15 atm to efface the waist of the stenosis [58]. Excluding initial failures, 20 percent of lesions in native fistulas and 9 percent in grafts required very high pressure (>20 atm) to efface the waist. Two (1 percent) could not be successfully treated with angioplasty despite the use of an ultra-high-pressure balloon. Residual stenosis was positively correlated with severity of initial stenosis and negatively correlated with duration of inflation.
Duration of dilatation — Another procedural variable associated with angioplasty is the optimal duration of dilation pressure. Common practice is to deflate the balloon immediately once the waist created by the stenosis is fully effaced. Because residual stenosis is an important factor in determining duration of patency [9,59], many interventionalists feel that a prolonged dilatation will decrease the chances of it occurring. However, based upon the studies below, we do not recommend a prolonged inflation time.
●Whether a prolonged inflation time is of value was addressed in a randomized trial that assigned 48 patients to either a one-minute or three-minute inflation period [60]. There was no significant difference in technical success rates between the groups. In addition, there were also no differences in the one-, three-, and six-month patency rates following treatment.
●In a retrospective review, 223 interventions divided between 30-second and one-minute inflations were compared (178 with 30 seconds and 45 with one minute) [61]. There was no significant difference between the two groups for either immediate technical success or patency in the first three months.
Handling multiple lesions — When multiple lesions are present that require treatment with angioplasty, treatment should start with the lesion that is the most proximal (downstream or central). This serves to decrease outflow resistance, which reduces the risk of vein rupture and helps to minimize the consequences of extravasation, should it occur. Another reason to start proximally is that it is much easier to pull a used angioplasty balloon back through a stenosis rather than advance a balloon profile through a tight narrowing.
However, this sequence is frequently not followed when both a peripheral and a central lesion are present. Unless the central lesion is very tight, it is customary to start with the peripheral lesion(s) first. This is done to avoid having to transition the larger balloon used for central lesions through peripheral stenoses going in and especially coming out. On the other hand, if the central lesion is severe and is causing a significant increase in intravascular pressure peripherally, it would be better to start there to assure an open outflow.
Risk of vein rupture — It is virtually impossible to predict when vein rupture will occur. However, there are a few situations where recognizing an increased risk is possible, and alternatives (stenting or surgical treatment) can be considered if the risk of treating a specific lesion is high.
●High intravascular pressure postangioplasty – There are instances in which an injured vessel might rupture due to excessive intravascular pressure.
•If there is excessive downstream (proximal) resistance to flow, the weakened wall of the vein may give way. Avoidance of this situation is the reasoning behind treating the most centrally located lesion first when there are multiple stenotic lesions. This approach assures an unobstructed outflow.
•An angioplasty site can rupture when performing a retrograde injection with the proximal access manually occluded. To reflux radiocontrast into the artery to obtain an arteriogram, the pressure exerted must exceed arterial pressure. The risk of rupture with a postangioplasty angiogram is particularly high following treatment of a juxta-anastomotic lesion. These angiograms should always be obtained by passing a vascular catheter slightly beyond the arterial anastomosis to avoid exposing the treated site to high intraluminal pressure.
●Excessive dilation pressure – The recommendation for a resistant lesion is an increased level of dilatation pressure. As with the elastic lesion, this approach is important for success of the treatment but carries with it an increased risk of complication.
●Oversized balloon – It is customary to use a slightly oversized balloon for venous angioplasty; however, if the balloon is excessively oversized, rupture of the vein can be anticipated. When an elastic lesion is encountered, moving to an only slightly larger (1 mm increase) balloon is recommended.
●Immature veins – Although it is recommended that all newly created AV fistulas should be evaluated at four to six weeks to identify and treat any problems interfering with development, it is very likely that immature veins are more susceptible to rupture. In this case, care should be taken not to be excessively aggressive.
●Collateral veins – With the development of venous stenosis, collateral veins often form. At times, when use of the primary vein is not possible, a collateral may be used to restore access flow. Although this is a good approach to salvage the AV access, the collateral veins are fragile and susceptible to rupture.
Prevention of vein rupture — The vessel wall that is injured by the angioplasty is initially protected from the elevated pressure by the expanded balloon, but as the balloon starts to deflate, the injured wall becomes exposed and susceptible until the balloon deflates sufficiently to dissipate the excessive pressure. To prevent this phenomenon, manual occlusion of the inflow during the angioplasty procedure and until the balloon is totally deflated has been recommended (figure 2). This prevents the sudden increase of pressure that would otherwise occur. Once the balloon is totally deflated, it is no longer obstructive, and the danger will have passed.
Postangioplasty angiogram — Once the venous lesions have been treated, it is important to leave the guidewire in place until the result of the angioplasty can be evaluated. If there is a complication, the presence of the guidewire may be essential for successful management. Following angioplasty, an angiogram should be performed to assess and document the result of therapy and identify the presence of any complications that might have occurred.
It is important to assess AV access inflow when assessing a dysfunctional graft. There are two easy and inexpensive ways to accomplish this: checking for pulse augmentation and visually assessing flow rate.
●Pulse augmentation (figure 3) is perhaps the best method to use for AV access inflow assessment. It is performed by simply feeling the pulse within the AV fistula or AV graft (this works much better with the AV fistula), then completely occluding the graft and feeling by how much the pulse increases (augments). The degree of augmentation is directly proportional to the quality of the access inflow. Again, with experience, this becomes a useful tool for assessing AV access inflow.
●With experience, it is possible to assess the speed of blood flow within the graft (or fistula) by observing the speed of the movement of a puff of radiocontrast as it traverses the access. It is important that one observe both the front end (beginning) and the back end (ending) of a short bolus of radiocontrast. If either is not seen, one gets the impression that there is no movement. This is a subjective assessment, but with experience it becomes a valuable tool.
If assessment of access inflow using these two methods suggests that it is not optimal, then a careful evaluation of the arterial anastomosis and feeding artery is indicated, although most interventionalists advocate assessing the inflow routinely in all cases. If an arterial inflow lesion is detected, it should be treated.
Balloon and sheath removal and hemostasis — Once inflated, an angioplasty balloon will be slightly larger than when it was inserted. It is often helpful to use a twisting motion to bring the balloon back into the sheath, a motion that wraps the "wings" of the deflated balloon back around the shaft. If difficulty is encountered in removing the balloon, the balloon and the sheath should be removed together rather than applying excessive force to pull the balloon into the sheath. This is particularly true with the removal of an angioplasty balloon that has ruptured. A broken fragment can catch on the sheath and be sheared off if excessive force is applied in balloon catheter removal.
Hemostasis can be obtained with manual pressure. However, special adhesive bandages are available that promote more rapid hemostasis. One such bandage (eg, TipStop) has a small plastic button covered with a layer of collagen in its center. The button applies pressure, and the collagen promotes thrombosis (picture 2). Another bandage (HemCon) contains chitosan (derived from shrimp shells), which provides rapid hemostasis. (See "Overview of topical hemostatic agents and tissue adhesives", section on 'External agents'.).
These bandages are relatively inexpensive and very effective in most cases. Using one of these devices, hemostasis can be accomplished within three to five minutes. Some interventionalists prefer to use a purse-string type of suture at the cannulation site [58]. If a suture is placed, provision must be made for removal within 24 to 48 hours; failure to do so can lead to skin necrosis, which increases the risk for infection.
PROCEDURE-RELATED COMPLICATIONS — As with any type of medical procedure, angioplasty can result in procedure-related complications; however, the reported complication rate is overall low. In a study involving nearly 250,000 angioplasty procedures for AV fistulas, the overall incidence of complications was 1.8 percent with the incidence of major complications only 0.36 percent [62]. In the same study, among nearly 115,000 AV grafts, the overall complication rate was 1 percent with major complications in only 0.22 percent.
Procedure-related complications are generally classified according to the reporting standards of the Society for Interventional Radiology [63]. According to this standard, all complications, including pulmonary and cardiac events that occur within 30 days following the procedure, are considered procedure related. Minor complications are those that require either no therapy or only nominal therapy and resolve without any adverse sequelae. Major complications are defined as those that require an increase in the level of care or result in hospitalization, permanent adverse sequelae, or death.
Complications of angioplasty can be related to vein spasm, vein rupture (eg, endothelial tear, extravasation, perigraft hematoma), or technical complications (eg, balloon rupture).
Vein spasm — Vein spasm can occur following any instrumentation of a vein (image 3). This is generally of no consequence, but it can be confused for a stenotic lesion. (See 'Pseudostenosis' above.)
Rarely, a patient may be encountered in whom it is a problem. Severe spasm can lead to thrombosis. Venous spasm, when it occurs, will generally dissipate within a few minutes. However, severe spasm can lead to AV access thrombosis. If spasm is generalized or prolonged and significantly affects access blood flow, consider nitroglycerine infusion, and if persistent, anticoagulation is indicated to prevent thrombosis.
Endothelial tear — When angioplasty is successful, it is generally due to a break or tear in the vessel wall. Sometimes an endothelial tear, or dissection, will cause a flap that interferes with blood flow (image 7). These can generally be managed by placing the angioplasty balloon across the affected area, inflating it with a soft pressure, and leaving it for three to five minutes to tamponade the flap against the wall [63]. Although this is generally successful, the maneuver can be tried a second time if flow is still adversely affected. The placement of a stent should be considered after tamponade has failed a second time. (See "Endovascular intervention for the treatment of stenosis in the arteriovenous access", section on 'Stenting'.)
Vein rupture with extravasation — Although injury to the vessel wall to some extent is important for successful angioplasty, at times the degree can be more than desired. This injury can take the form of a simple tear or an actual rupture with the extravasation of blood and/or radiocontrast into the surrounding tissue. Extravasation of blood or radiocontrast is the most frequent procedure-related complication seen in association with angioplasty is vein rupture [64]. In a study involving nearly 250,000 angioplasty procedures performed on AV fistulas, 78 percent of all complications were related to vein rupture, with 60 percent classified as minor (requiring no treatment) [62]. Of the nearly 115,000 AV graft cases, vein rupture with extravasation accounted for 64 percent of complications, and 48 percent were classified as minor.
It is difficult to predict when vein rupture might occur. However, there are a few situations when the risk for rupture when treating a specific lesion is more than is acceptable. Measures to prevent vein rupture are discussed above. (See 'Risk of vein rupture' above.)
Extravasation has been classified into four categories with implications for management.
●Subclinical extravasation of radiocontrast – Blush of radiocontrast adjacent to vein
●Grade 1 extravasation – Extravasation that is stable and does not affect blood flow
●Grade 2 extravasation – Extravasation that is stable but affects blood flow
●Grade 3 extravasation – Extravasation that is not stable, disruption of vein
The clinical significance of vein rupture with extravasation is variable, ranging from none to disaster for the AV access. The difference lies in the extent of the tear and degree of surrounding soft tissue incorporation of the access conduit. This event is generally heralded by the extravasation of radiocontrast, blood, or both. It becomes most obvious when there is the formation of an obvious hematoma. The amount of extravasated radiocontrast associated with the hematoma may be minimal or absent. The size of the hematoma is not particularly important in determining the sequelae with which it is associated. One may see a small degree of extravasation with hematoma formation because of complete vein disruption that was quickly controlled, and a very large hematoma may be completely stable and have no effect on blood flow.
Once it is obvious that vein rupture with extravasation has occurred, the access inflow should be manually occluded. This relieves pressure on the site and limits the degree of extravasation until the severity category (ie, stable/not stable, affecting flow/not affecting flow) can be assessed.
Subclinical extravasation of radiocontrast — Occasionally, during an angioplasty procedure, a blush of radiocontrast adjacent to the vein at the site of the dilation is observed but there is no associated hematoma (image 8). This small extravasation is asymptomatic and only obvious on fluoroscopy. An ecchymosis may become apparent if it is superficial, but, regardless, no treatment is required [65]. Most interventionalists do not list a subclinical extravasation as a complication.
Grade 1 extravasation — A grade 1 extravasation is stable (ie, not continuing to expand) and does not affect flow (image 9). In general, a grade 1 extravasation that remains stable over 30 minutes to one hour will continue to behave in this manner provided there is no downstream obstruction. Localized discomfort may be significant and may last for several days. Although it may cause concern on the part of the operator and the patient, it is of no real consequence with respect to the outcome of the procedure and requires no specific treatment or any ongoing observation, regardless of size; however, the patient may require symptomatic treatment measures [65]. Mild analgesics and a heating pad may be helpful. A grade 1 hematoma should be classified as a minor complication since no treatment is required and there is no adverse sequela.
Grade 2 extravasation — If an extravasation is stable but affects flow, it is classified as a grade 2 extravasation, regardless of size (image 10). Most of these lesions stabilize very quickly after they form. In these cases, the rupture that has occurred will require treatment to restore AV access flow. The grade 2 extravasation is classified as a major complication of AV access angioplasty even if treatment is successful since treatment was required.
Treatment of this lesion consists of angioplasty balloon tamponade for a period of four to five minutes. Once the balloon is in position, it should be inflated with a pressure that is only necessary to fully expand the balloon (generally 2 to 4 atm). The use of higher pressures could make the tear worse. The goal of treatment is to press the flap outward and compress the extravascular accumulation to open the lumen and restore flow. Once the lumen is opened with an angioplasty balloon, the sustained pressure of the balloon (tamponade) tends to stabilize the situation after a few minutes and allow for the restoration of flow. This return of flow helps to keep the offending flap in position.
If flow continues to be significantly affected after the tamponade procedure, the procedure should be repeated. If the problem continues, placement of a covered stent should be considered [66-68]. If there is any downstream resistance (from a stenotic lesion that has not yet been treated, for example), this must be relieved. If the downstream intravascular resistance is greater than the resistance of the perivascular tissue, extravasation will continue.
Grade 3 extravasation — A grade 3 extravasation is an unstable extravasation with ongoing active bleeding. This is a result of a complete or near-complete disruption of the vein. Hematoma formation generally occurs very rapidly, but the size of the extravasation can be quite variable and primarily depends on how quickly it is recognized and controlled. The extravasation can become quite large if not recognized early, as in the case where the arm is covered by a drape. Balloon dilatation is somewhat painful; however, after the balloon is deflated, the pain should disappear. If the patient continues to complain of pain, extravasation should be suspected.
When a grade 3 extravasation occurs, there is a real risk of losing the AV access. The first goal in the management of a grade 3 extravasation is to limit its size. As soon as the situation is recognized, the access inflow should be manually occluded to arrest further extravasation [65]. Placement of a covered stent across the disruption should be attempted and is often successful (image 11) [66,69]. If this is not successful, the access should be occluded. To accomplish this, inflate an angioplasty balloon to a low pressure within the access below the site of rupture, typically overnight, with the patient admitted to the hospital for observation. Once the access is thrombosed, the angioplasty balloon can be deflated and removed. Emergency surgery is not usually necessary; however, the patient will require a new dialysis access for both the immediate and long term.
Angioplasty balloon rupture — Fortunately, when an angioplasty balloon "ruptures," it does not explode; rather, the balloon is designed such that when the tolerance pressure of the balloon is exceeded, the attachment of the balloon to the catheter (weld-point) simply loosens, giving way and spilling the balloon's contents. If the structural integrity of the balloon material is actually disrupted, the balloon design is such that a linear tear should develop. Unfortunately, in spite of the precautions that have been taken in the manufacturing process, occasionally an angioplasty balloon does rupture with a circumferential tear, and if this occurs, there is the risk that a balloon fragment can embolize, which can occur at the time of rupture. A fragment of a ruptured balloon might also shear off when it is being extracted through the sheath. For this reason, any time that resistance occurs when a balloon is being removed, it is best to stop and remove the sheath along with the balloon as a unit as mentioned above.
Once a ruptured balloon has been extracted, it should be carefully examined to determine if a fragment has been left behind. When there is a circumferential tear and a fragment of the balloon has been left behind, in most cases, the fragment is still on the guidewire. For this reason, the guidewire should never be prematurely removed when there is a suspicion that a balloon fragment has been left behind. An angiogram can confirm that the fragment lies at some point along the course of the retained guidewire (figure 4). A second guidewire should be passed and used to insert a snare, which can be used to catch the distal end of the primary guidewire and extract it. With this task complete, the operator will have both ends of the guidewire in hand with the balloon fragment on the looped guidewire. At this point, extraction is achieved by simply removing the guidewire along with the retained fragment. It may be necessary to remove the sheath as this is being done.
TREATMENT SUCCESS — The goal of the angioplasty treatment should be the complete elimination of the lesion. Residual stenosis of any degree is a problem and should not be accepted. In a prospective study of 330 angioplasty procedures designed to identify predictors of AV graft patency after intervention, the median access survival was inversely related to the magnitude of residual stenosis [59]. With complete resolution (ie, no residual stenosis), the primary patency was 6.9 months; by comparison, it was reduced to 4.6 months with any residual stenosis.
Because not all reports have specified their criteria for success, it becomes necessary to evaluate each report individually and carefully to determine what is meant by their study author's usage of the term "successful angioplasty."
Technical success rates for angioplasty vary according to the location of the lesion. Overall success rates can be misleading. The best approach is to look at individual lesion types. Two broad categories of venous lesions are seen: central vein stenosis and peripheral vein stenosis. Two special areas that should be evaluated separately are the venous anastomosis of an AV graft and lesions of the cephalic arch. These two areas are somewhat unique in their response to angioplasty.
Central vein stenosis — Reports of angioplasty treatment for central venous stenosis have demonstrated a variable technical success rate ranging from 70 to 90 percent [3-9,70]. The primary and primary assisted patency rates for angioplasty treatment also have wide variability. The reported six-month primary patency rate has ranged from 23 to 63 percent with primary assisted patency rates of 29 to 100 percent. The 12-month primary patency rate ranges from 12 to 50 percent with a primary assisted patency rate of 13 to 100 percent [2,35,71-77].
Lesions in the central veins tend to be elastic, and it has been speculated that there are both elastic and inelastic lesions based upon their response to angioplasty. In a series of 30 patients, two cases (7 percent) were technical failures [71]. Of the 28 in whom angioplasty was successful, 21 (70 percent) had 50 percent or greater improvement in the luminal diameter of the lesion, and 7 (23 percent) showed no improvement due to elasticity of the stenosis. Subsequently, 81 percent of successful (nonelastic) cases restenosed at an average of 7.6 months, while 100 percent of elastic lesions were occluded in an average of 2.9 months. The authors of this study proposed stenting for the elastic lesions.
Most patients with an AV dialysis access have extremely large central veins. With central vein stenosis, the veins tend to be even larger. Based on angioplasty balloon sizes that are available, it is likely that the recommendation for oversizing the angioplasty balloon 10 to 15 percent is generally not possible (and not recommended because of the increased level of complications that could be encountered in the case of a vein rupture). In addition, it is very likely that the problem in cases with very large central veins is a high Qa and flow reduction is indicated rather than angioplasty.
Peripheral vein stenosis — Angioplasty has its greatest success in the treatment of peripheral venous stenosis. Initial success (technical success) rates for angioplasty have ranged from 87 to 99 percent for peripheral venous stenosis associated with AV grafts [2,3,35,59,62,64,76,77] and 79 to 99 percent for AV fistulas [2,62,64,78-83]. The largest of these involved a series of 114,522 AV graft cases and 241,019 AV fistula cases, which had a 98.9 and 98.5 percent initial success rate, respectively [59].
Reports have indicated that approximately 20 to 30 percent of patients fail to show an increase in blood flow after what had been judged to be a successful angioplasty based upon anatomical criteria [84-86]. The reasons for this hemodynamic failure are not clear but are undoubtedly related to residual stenosis, elasticity, or a missed lesion.
Primary patency rates for angioplasty of peripheral vein stenosis in AV grafts have ranged from 42 to 69 percent at six months and 31 to 45 percent at one year [2,3,35,58,59,70,87-90]. Assisted primary patency rates have been in the range of 72 to 87 percent in the few reports in which this statistic has been available [3,78].
Peripheral venous lesions treated with angioplasty in AV fistulas have shown a six-month primary patency ranging from 43 to 71 percent with a six-month assisted primary patency of 84 to 89 percent [64,75,91-95]. For one-year primary and primary assisted patency in peripheral vein stenosis associated with AV fistulas, the range has been 39 to 64 percent and 81 to 86 percent, respectively [8,64,78-82]. The data for AV fistulas should be interpreted with a degree of caution. The most commonly occurring lesions with this type of dialysis access are within the access itself. There is always the possibility that these lesions behave differently than those occurring in the draining veins.
Cephalic arch stenosis — Stenosis at the cephalic arch has been reported to be present in 15 to 18 percent of cases of AV fistula failure [83,96]. It is much more common in association with brachial-cephalic AV fistulas than with radial-cephalic [83,96-98]. One study reported a 39 percent incidence in brachial-cephalic AV fistulas compared with 2 percent in radial-cephalic. In another report, the incidences were 77 and 20 percent, respectively [98].The explanation for this difference is thought to be related to the level of blood flow through the cephalic arch [85]. Blood flow through cephalic arch is generally higher for a brachial-cephalic compared with radial-cephalic AV fistula given that the flow rate of a brachial artery AV fistula is higher, in general, and all of the blood flow of a brachial-cephalic AV fistula goes through the cephalic arch, whereas in a radial-cephalic AV fistula, there is the possibility for a division of blood flow to both the basilic and the cephalic vein. In some instances, all or the majority of flow actually misses the cephalic arch.
Angioplasty at this site is problematic. In a series of 1118 procedures performed in AV fistulas and AV grafts, there were 74 upper arm AV fistulas [56]. Lesions resistant to angioplasty occurred in 4.8 percent of the upper arm AV fistulas, and the majority of these were within the cephalic arch. A venous rupture rate of 14.9 percent was observed in the upper arm, and, again, most were within the cephalic arch.
In another study of 50 percutaneous angioplasties in 26 AV fistulas with cephalic arch stenosis, anatomic success was 76 percent while clinical success was 98 percent. Higher inflation pressures (>15 atm) were needed in 29 (58 percent) of the cases. Rupture occurred in 6 percent of cases (3 out of 50), one of which led to AV fistula loss [96]. The other two cases were salvaged with prolonged balloon inflation or stenting. Primary patency was 42 percent at six months and 23 percent at one year (median primary patency of five months). Primary assisted patency was 83 percent at six months and 75 percent at one year (median three years). An average of 1.6 procedures per year was required per AV fistula. This venous rupture requiring a therapy rate of 6 percent is placed into context when it is compared with a series of 1561 AV fistula angioplasties (all types) that reported a rupture rate of 0.23 percent [59].
Long-term patency rates for cephalic arch angioplasty generally range from 41 to 76 percent at six months and 31 to 45 percent at one year [2,3,58,59,70,87-89]. The conclusion that one can draw from the available data concerning angioplasty of cephalic arch stenosis is that primary success is suboptimal. However, the lesion is more resistant to dilatation, is more likely to be associated with complications, and has a shortened long-term patency rate as compared with other sites [90]. Covered stents in this location may hold promise.
AV graft arteriovenous anastomosis stenosis — The most common site for the development of stenosis relating to an AV graft is the venous anastomosis. In a review of 2300 cases of AV graft stenosis, this was the location of the lesion in 60 percent [70]. Unfortunately, this is also a difficult area in which to obtain prolonged patency following angioplasty. The reasons for this are thought to be related to the very aggressive nature of the neointimal hyperplasia that occurs at this site of marked turbulence and the fact that the lesion also incorporates the inelastic synthetic graft material. There have been only a few studies that have reported patency results specific for this lesion [2,99,100]. Most of these represent the control group for stent studies. In these series, the primary patency rate at six months ranges from 20 to 67 percent with an assisted primary patency (based on a single study) of 76 percent [99].
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Dialysis" and "Society guideline links: Hemodialysis vascular access".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Beyond the Basics topics (see "Patient education: Dialysis or kidney transplantation — which is right for me? (Beyond the Basics)" and "Patient education: Hemodialysis (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Patient evaluation – Most patients are referred for angiography because of clinical or physiological abnormalities detected at the dialysis clinic. Prior to the procedure, it is important for the interventionalist to confirm the findings and assure with reasonable certainty that a treatable lesion is present prior to proceeding. The examination, which ideally includes duplex ultrasonography, also helps plan the intervention. Patients with a high AV access flow rate (Qa) may benefit from a flow reduction procedure, rather than proceeding the angiography and possible angioplasty. (See 'Patient evaluation' above.)
●Angiography – An angiogram should be performed to evaluate the anatomy of the AV access and its draining veins prior to treatment of any specific lesion. It is important to evaluate the entire access circuit through to the superior vena cava since multiple lesions are often present. (See 'Pretreatment angiogram' above.)
●Criteria for treatment – Clinically significant lesions that represent 50 percent stenosis or greater should only be treated if shown to be associated with decreased access flow rate (Qa). The percent stenosis is determined by comparing the lesion with the diameter of the adjacent "normal" vessel; however, measurement of the degree of stenosis for an AV fistula or central venous lesion can be challenging. Following treatment, it is very important that clinical or physiological abnormalities that were present prior to treatment are re-evaluated as early as practical. These abnormalities should be resolved after the procedure. (See 'Treatment criteria' above.)
●Angioplasty – Angioplasty involves passing a wire through identified stenotic lesion(s) over which a noncompliant balloon catheter of appropriate length and diameter (oversized by 10 to 15 percent) is placed. The balloon is inflated (syringe, commercial device) to its rated pressure (15 to 20 atm) for about a minute to expand the lesion by creating a controlled dissection. A variety of balloon types are available (high pressure, ultra-high pressure, cutting, drug-coated) the use of which are tailored to the specific clinical situation. Multiple lesions are ideally approached by managing the most proximal (downstream/central) to reduce outflow resistance before handling peripheral lesions. Technical success rates for angioplasty vary according to the location of the lesion. (See 'Angioplasty technique' above and 'Treatment success' above.)
●Complications – The complication rate for angioplasty of hemodialysis AV access is overall low with major complications occurring in <1 percent. Complications related to angioplasty include predominantly venous spasm, which can lead to thrombosis; balloon rupture, which rarely can fragment; and vein rupture with varying levels of extravasation. Vein rupture can often be managed with balloon tamponade or the use of a covered stent. Occlusion of the graft is sometimes needed to control severe bleeding. (See 'Procedure-related complications' above.)
●Recurrent stenosis – Recurrent stenosis can usually be successfully treated with repeat angioplasty. For patients with recurrent stenosis for which angioplasty was required more than two times within three months, surgical revision should be considered. (See 'Recurrent stenosis' above.)
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