Tabla 1. Demographic characteristics.

Figura 1. Fistulography findings.

Figura 2. Angioplasty of PAVF. Severe inflow stenosis (juxta-anastomotic) of humero-axillary prosthe...

Figura 3. Central venous angioplasty ofNAVF. Severe outflow stenosis (at the jugular-subclavian con...

Figura 4. Central venous angioplasty of NAVF. Left subclavian vein stenosis of humero-axillary NAVF....

INTRODUCTION

Cardiovascular disease is the lead cause of mortality in patients on hemodialysis and represents > 50% of the deaths reported due to known causes. In addition, mortality is 9 times higher in these patients compared to individuals of the same age and sex of the overall population.1

Vascular access for ideal hemodialysis is the one that provides reliable and uncomplicated access to administer the dialysis prescribed. At the same time, it should be based on the needs of each patient.2

The first vascular access option advised is the native arteriovenous fistula (NAVF) over the prosthetic arteriovenous fistula (PAVF), and the latter over the central venous catheter.2 If possible, inside the NAVFs, the option most distal to the non-dominant extremity should always be selected.2,3

The rates of primary patency at 6-and-18-month follow-up for NAVFs are 72% and 51%, and for PAVFs somewhere between 58% and 33%.3

The KDOQI guidelines consider it reasonable that when clinical monitorization is indicative of a vascular access damage (stenosis), imaging modalities should be used on such access (experts’ opinion). Selecting the imaging modality that should be used depends on local resources (in our case the imaging modality selected is fistulography.2)

Vascular access flow dysfunction refers to clinically significant abnormalities in the flow or patency of vascular access due to underlying stenosis, thrombosis, or related conditions.2 In 85% to 90% of the cases thrombosis has been associated with underlying venous stenosis.5

Anatomically significant stenosis with a reduction > 50% of the vessel normal diameter is accompanied by hemodynamic or clinical abnormalities like changes to the characteristics of the fremitus, swelling to the access extremity, prolonged bleeding, difficulty puncturing the access site, and performing hemodialysis, presence of collateral veins and/or aneurysms, elevated venous pressures during treatment, reduced intra-access blood flow, elevated pre-pump negative arterial pressures, and abnormal recirculation values.3,5

The techniques proposed to resolve the stenotic complications of these vascular accesses have been different. However, these could be categorized into surgical and percutaneous techniques. There is consensus on the endovascular treatment of central vessel stenoses like those of the fistula puncture path. Juxta-anastomotic stenosis of both NAVFs and PAVFs could be treated both through surgery and interventional procedures.3 We should mention that KDOQI guidelines consider reasonable to use balloon angioplasty as the first-line therapy of stenotic lesions to treat both NAVFs and PAVFs (experts’ opinion).2

Regarding percutaneous techniques, different studies have compared the use of percutaneous transluminal angioplasty (PTA) with conventional balloons, drug-eluting balloons, or venous stents to treat stenoses of AVFs.6-10 To this date, no proper evidence has come up to give any kind of recommendations on this regard.2

MATERIALS AND METHODS

This was a retrospective, observational, and multicenter study that included patients with end-stage chronic kidney disease (stage V hemodialysis) treated at the Department of Hemodialysis of a Santa Fe hospital in Argentina. Several fistulographies were performed due to suspected stenotic complications of AVFs during renal replacement therapy from January 2016 through October 2022.

A total of 59 patients were included [21 women (35%) and 38 men (64%)]. The patients’ mean age was 64 ± 8 years while 54% of the sample showed diabetes as the main risk factor. The remaining demographic characteristics are shown on Table 1.

The reasons why the fistulography was indicated were venous hypertension in 40% of the cases followed by access thrombosis in 27% of the cases, and inadequate Kt/V in 15% of the cases.

The most widely used access route was direct puncture of the AVF, the femoral veins, or the jugular veins in 87%, 10%, and 3% of the cases, respectively.

The most widely used vascular access in our population was NAVFs in 16 patients (27%) followed by PAVFs in 39 (66%), and permanent venous catheters in 4 (6%).

Definitions

Fistulography is defined as the angioplasty performed to assess the circuit of hemodialysis including the arterial anastomosis site, fistula or graft, and outflow veins including the ipsilateral central veins, the vena cava, and the right atrium.5,11

Within the categorization of the stenosis site, we rather use a functionality criterion with respect to the puncture site by classifying stenoses into inflow stenoses (found in the nutritious artery, anastomosis itself, or in the early trajectory of the arterialized vein up to 5 cm after anastomosis), and outflow stenoses (venous stenoses of the puncture path all the way up to the right atrium including central venous stenosis). Also, we rather distinguish central stenoses from all the other stenoses because they have a completely different physiopathological mechanism.3 The stenoses of NAVFs that compromise the junction between the prosthesis and the vein are called juxta-anastomotic stenoses.

The hemodynamic or clinical abnormalities that triggered the performance of fistulographies were clinical signs of venous hypertension (arm swelling, vascular access dysfunction, increased collateral circulation, etc.), increased dynamic venous pressure (defined as venous line pressure values > 150 mmHg or a 25% increased with respect to the baseline value in 3 consecutive sessions), past medical history of access thrombosis, lack of NAVF maturation, inadequate Kt/V (spKt/V of 1.4 per session of hemodialysis for patients treated 3 times/week with a minimum spKt/V administered of 1.2 or an online Kt of 40-45 liters for women, and 50-55 liters for men).2,3,12-14

Patency after the creation of the arteriovenous fistula is defined as the period elapsed from the creation of the fistula until the performance of the first elective procedure. On the other hand, post-PTA patency is defined as the time elapsed from the elective procedure until the indication of a new fistulography.

Successful angioplasty is defined as reduced stenosis > 50%.5

Failed angioplasty is defined as residual stenosis > 50%.5

RESULTS

In 13 (22%) out of all the patients studied (Figure 1) no angiographically significant lesions were found; in 22 (37%) inflow lesions were found most of them juxta-anastomotic since they were found in the PAVFs (86%). In 24 patients (40%) outflow lesions were found, most of them located in central veins (74%) and closely associated with prior use of venous catheters at that location.

The stenotic lesions of 46 patients were treated with endovascular treatment through percutaneous balloon angioplasties in 76% of the cases (35 patients). Surgery was used in inflow stenosis with arterial compromise in only 24% of the cases (11 patients).

The balloons used for endovascular treatment were conventional balloons depending on the target vessel diameter [somewhere between 3.0 mm and 6.0 mm for inflow lesions (Figure 2), and between 8.0 mm and 16 mm for outflow lesions (Figure 3)], achieving success rates close to 95% with reduction of stenotic section in over 50% of the patients. The access routes used for endovascular therapy were direct puncture of the fistula in inflow stenoses, and mostly femoral access for the management of outflow lesions.

In 15 of all the patients treated with endovascular treatment (35 patients) the presence of lesion restenosis was confirmed within the first 6 to 12 months following the procedure (42.8%). In these cases, we chose to perform reinterventions with new balloon angioplasties with successful results in the end.

A total of 62.5% and 27.5% of all the re-stenoses seen were found in the PAVFs and NAVFs, respectively.

Lesion relapses were confirmed in 10 cases (28.5%) out of all the patients with restenosis, which is why reintervention with angioplasty followed by venous stent implantation was used (Figure 4). All were cases of outflow central lesions.

The complications associated with balloon and venous stent angioplasties were scarce: just 1 case of a mild allergic reaction to contrast, and another case of access site thrombosis after the procedure.

The 12-month rates of patency after endovascular therapy of all the patients studied regarding NAVFs and PAVFs were 59.9% and 47.3%, respectively.

DISCUSSION

Currently, it is being discussed whether PTA can or cannot replace or compete with surgery. For PTA to compete with surgery, it should achieve primary patencies at 6 months in 50% of the cases. Glanz and Beathard, in two articles, report annual patency rates with PTA around 38%. Former studies have obtained higher patency rates with surgery (Brooks) while others with percutaneous therapy (Dapunt). Currently, and according to recent studies, it seems demonstrated that the PTA achieves patency rates above the aforementioned 50%, which means that it should be the technique of choice in the management of venous stenosis in AVFs.

CONCLUSIONS

Although our study has some limitations since the study sample was small, we believe, given the post-angioplasty patency obtained 12 months after the creation of NAVFs (59.9%) and PAVFs (47.3%) that the arrival of new endovascular techniques provides safe, easy, and effective tools for the diagnosis and treatment of arteriovenous fistulas, thus achieving greater durability in the patency of these.

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Stenotic complications of arteriovenous fistulas and resolution via percutaneous transluminal angioplasty

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