Role of Endovascular Treatment in Dysfunctional Hemodialysis Fistulae: A Single Center Experience

Introduction

The incidence of chronic kidney disease (CKD) is on the rise throughout the world. A population-based study estimated an age-adjusted incidence rate of end-stage renal disease (ESRD) to be 232 per million in the Indian population.[1] ESRD patients can also be on conservative treatment such as peritoneal or hemodialysis before they undergo transplant. Out of these, hemodialysis is the safest and most acceptable method. Hemodialysis requires creating a vascular access, which can be done by arteriovenous fistulas (AVFs), arteriovenous grafts (AVGs), and tunneled or non-tunneled catheters.[2]

AVFs are the preferred route of hemodialysis as they have lower morbidity and better patency results. However, creating a long-term AVF access is a challenge as approximately 50% of fistulas lose patency during the course of treatment.[3] However, with the advancement of endovascular procedures, the patency of AVFs for hemodialysis can be prolonged by various procedures, including percutaneous transluminal angioplasty (PTA); thromboaspiration, and vascular stenting.[4]

The study aimed at evaluating the role of endovascular procedures in various types of fistula dysfunctions at various anatomical sites, their indications, efficacy, and short-term patency.

Materials and Methods

This was a retrospective observational study based on the results of various endovascular procedures carried out for dysfunctional endovascular fistulas in the Department of Radio-Diagnosis & Interventional Radiology of a tertiary hospital in the Himalayan foothills done for a period of 1 year from September 2020 to August 2021.

Results

The study group comprised 46 patients who underwent endovascular treatment for dysfunctional hemodialysis fistulas at our department during the study period. The study group consisted of patients ranging from 29 to 80 years of age with a mean age of 50.90 years. Maximum patients presented in the sixth decade. Males dominated the study population (n = 29). Hypertension was the most prevalent comorbidity (n = 32, 72.72%) followed by diabetes (n = 25, 56.81%). The demographic profile of the study population is depicted in Figure 1 and Table 1.

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Figure 1

Age distribution of the study group

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Out of 46 patients, 36 had stenosis at the fistula site and had to undergo PTA. Accessory veins were observed in three cases, and aneurysmal dilatation on the venous side of the fistula was seen in two cases. These patients were referred to a vascular surgeon for further management. Furthermore, 19 out of these 36 patients who had associated thrombosis underwent additional pharmacomechanical thromboaspiration. The rest of 10 patients, had CVS for which endovascular stenting was done after PTA.

It was observed that left-sided fistulas (n = 30, 65.21%) were more common than right-sided (n = 16.34.78%) fistulas. The most common anatomic site of fistulas in the study group were brachiocephalic (n = 24, 52.17%), followed by radio cephalic (n = 19, 39.13%) fistulas. The least common variety in the study group was brachio-basilic fistulas (n = 4, 8.69%). Among the central veins, the most common site of narrowing was subclavian vein (n = 6) followed by brachiocephalic and axillary veins in four cases each. Most of the patients presented to us after 1 year of fistula creation (n = 25, 54.34%), while 18 patients (39.13%) presented within 6 months of fistula formation. Fistula characters are depicted in Table 2.

The most common cause of dysfunction within the fistula was juxta-anastomotic stenosis seen in 33 of 36 patients of AVF stenosis, which comprised 91.66% of the subgroup. This was followed by venous and arterial stenosis/thrombosis in 11 and four cases, respectively. In most of the cases of CVS, the length of the dysfunctional segment was more than 5 cm, while a segment length of less than 3 cm was common in patients presenting with only juxta-anastomotic narrowing. The mean dysfunctional segment length in the study group was 5.08 cm. The profile of dysfunctional AVFs is depicted in Table 3.

Angioplasty balloon dilatation was done in 17 cases, out of which 15 resulted in technical success (88.23%). Out of these, 13 cases underwent at least one hemodialysis session and were marked as clinical successes (76.43%). Additional pharmacomechanical thromboaspiration was required in 19 cases, which resulted in a lower technical and clinical success rate of 84.2% and 73.6%, respectively. Endovascular balloon angioplasty and stenting was done for all 10 cases of CVS, which had a 100% success rate [Figure 2].

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Figure 2

Success rates of various endovascular procedures (PMT = Pharmacomechanical Thromboaspiration)

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Technical failure was observed in five cases (10.86%). The reason for technical failure was cephalic arch stenosis in two cases, where stenosed segments could not be cannulated and accessory veins in one case. In all cases with technical failure, the stenotic segments had thrombosis in the juxta-anastomotic segment or adjacent arterial or venous channels.

Post-procedure complication rate was low, with one patient presenting with acute thrombosis and one patient with puncture site hematoma.

Overall technical successes after a single endovascular intervention were seen in 41 patients (89.13%). Patients had undergone hemodialysis on the next day of the endovascular procedure, and 37 patients could have at least one successful session of hemodialysis post procedure, yielding a clinical success rate of 80.43%. Within the first week of procedures, three cases presented with reocclusion, one of them with acute thrombosis. Re-intervention was attempted in all three patients, out of which two were successfully opened and underwent dialysis sessions. Patients were followed up at 1 and 3 months in case of optimal dialysis sessions or on an emergent basis as per requirement. Angioplasty with thromboaspiration was attempted in a patient with re-occlusion at 1 month; however, it had to be abandoned. Another reattempt at angioplasty was done for a restenosis of juxta-anastomotic segment occlusion and was successful. The PIPP for the overall study population was 82.60% at 1 week, 80.43% at 1 month, and 78.26% at 3 months. The PIAPP was 86.95% at 1 week, 84.78% at 1 month, and 82.60% at 3 months [Table 4 and Figure 3]. A representative case is shown in Figure 4.

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Figure 3

Kaplan–Meier graphs depicting the survival analysis for post-intervention primary patency and post-intervention assisted primary patency in the study group

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Figure 4

(a) Pre-procedure angiogram shows juxta-anastomotic stenosis in radio cephalic fistula with non-opacification of cephalic venous channels. (b): Balloon dilatation of the stenotic segment. (c) Post-procedure angiogram shows technical success with the near-complete opening of stenotic site and opacification of arterial, juxta-anastomotic, and venous channels

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It was observed that stenotic dysfunctional segments undergoing angioplasty dilatation had better technical (88.23%) and clinical success rates (76.47%) than thrombotic dysfunctional segments that underwent additional thromboaspiration with PTA (technical success rate: 84.2%; clinical success rate: 73.6%). However, at the end of 3-month follow-up, it was observed that the thrombotic dysfunctional segments had better PIPP (73.7%); in contrast, once re-intervention was done, the PIAPP was better in the stenotic subgroup undergoing angioplasty dilatation (82.37%).

Discussion

AVFs have been the cornerstone for hemodialysis in ESRD patients for the past many years. Among other options of grafts and tunneled catheters, AVFs have the advantages of being less prone to infections, better patency, and lower overall morbidity. Hemodynamically significant stenosis is a common occurrence in AVFs and may require multiple attempts of endovascular treatments in the form of PTA with or without thrombolysis. When the stenotic segments involve the central veins, PTA may be accompanied or followed by stenting to maintain patency.[910]

The demographic profile of the study group showed male predominance (n = 29, 63.04%), with the most common decade of presentation being the sixth decade.[91112] There was high prevalence of hypertension and diabetes in the study group, similar to the results of Al Gaby et al.[12] and Hendawy et al.[4] This is compatible with the fact that diabetic nephropathy is the most common cause of chronic renal disease in the Indian population.[1]

As per the anatomical site, the best post-procedural success was seen in radio cephalic fistulas (94.4%), followed by brachiocephalic fistulas (87.5%).[12] The most common site of stenosis was juxta-anastomotic segments (n = 33, 71.73%), followed by venous (n = 11, 23.91%) and arterial stenosis (n = 4, 8.69%). Most successful outcomes were seen in the juxta-anastomotic segmental stenosis with 84.84% success, followed by venous stenosis with 63.63% success. Involvement of cephalic arches in two cases led to failures of PTA due to non-cannulation of the stenosed segments. CVS was successfully opened in all 10 cases who underwent PTA and stent placement. The profile of dysfunctional segment in the study group was similar to the findings of Takahashi et al.[7] and Le et al.[13]

The overall technical success rate in the study group was 89.13%, and the clinical success rate was 80.43%. This may be attributed to the fact that most patients presented to us after 1 year of fistula formation, which has been related to better endovascular procedural results in the literature.[12] Similar observations were made by Heye et al.[10] with technical success rates of 87.1% and a clinical success rate of 73.2% after PTA in their study group. They also observed that radio cephalic fistulas had the highest PTA success rates of 94%. While studying stenotic fistulas, Aktas et al.[9] reported a technical success rate of 96.3% with a recurrence rate of 23.2% in short-term follow-up. Hendawy et al.[4] reported a success rate of 88.3% while studying dysfunctional fistulas. Machado et al.[14] reported a 91% success rate for endovascular procedures in stenotic arteriovenous fistulas.

In patients with associated thrombosis, success rates in the published literature range from 60% to 100%.[1516] For thromboaspiration, Çildağ et al.[11] reported a technical success rate of 83%, comparable to the results of present study (84.2%, n = 16).

CVS has been typically addressed with PTA, with high technical success rates of 70%–90%. However, recurrent stenosis post PTA yields considerably lower primary patency rates of 12%–50% at 1 year.[17] Stenting with metallic stents earlier and now with covered stents is often done along with PTA to improve long-term patency in CVS. Stenting may be done after failed PTA with recurring stenosis or primarily along with PTA.[17] The technique of PTA with primary stenting was followed in the present study group. Following the same, all ten patients of CVS were taken up for PTA and stenting with a 100% success rates and 100% primary patency at the end of 3 months. Ashwal et al.[18] also reported 100% success in ten patients of CVS undergoing PTA and stenting.

Because the durability of hemodialysis fistulas is limited and previous literature suggests primary patency rates of 26%–62% at the end of 1 year, it is essential to follow up patients after endovascular treatment to assess the patency rates after various procedures in setting of a multitude of anatomical and clinical variables.[9] After confirmation of clinical success as proved by at least one optimal hemodialysis sitting post intervention, patients were followed up at 1 and 3 months after the first intervention procedure. Wherever required, re-intervention was done by PTA with or without thromboaspiration.

The PIPP was 78.26% and PIAPP was 76.08% at the end of 3 months in the total study population. With better PIPP in the PTA plus thromboaspiration subgroup at 73.7% in comparison to the PTA subgroup (70.5%), it was deciphered that requirement of re-intervention was slightly more in the stenotic-only subgroup within the follow-up period. On the contrary, once re-intervened, PIAPP was higher in the PTA subgroup at 82.35% compared to those fistulas where stenosis was associated with thrombosis (73.68%), thereby indicating that re-thrombosis after primary intervention is related with early fistula failure. Recurrent endovascular injury in multiple procedures and associated comorbid factors that have been associated with reduced patency time periods can also be the reason of a lower PIAPP in this subgroup.[8]

Hendawy et al.[4] and Reffat H et al.,[19] while studying similar fistula profiles, reported a primary patency rate of 82% and 81%, respectively, at 3 months follow-up. Çildağ et al.[11] reported that post thromboaspiration, primary patency rates were as low as 55% at 3 months. In a multicenter prospective trial by Huijbregts HJ et al.,[20] PIPP and PIAPP at the end of 3 months were documented as 83% and 92%, respectively; however, their study population had a more homogenous profile of dysfunctional fistulas.

Overall, the results of PTA versus PTA with pharmacomechanical thromboaspiration were comparable in our study group. Although a slight edge was seen in the post-procedural patency after multiple procedures in the angioplasty group, the difference was not statistically significant.

The profile of AV fistulas associated with most successful outcomes post endovascular intervention was radio-cephalic fistulas that were formed more than 1 year ago, with juxta-anastomotic narrowing and a mean length of dysfunctional segment <3 cm. Cephalic arch stenosis and accessory veins had the worst post-intervention outcome in our study group.

Conclusion

Endovascular intervention is the first-line treatment in dysfunctional arteriovenous fistulas as there is a multitude of options available for a variety of dysfunctions. Percutaneous angioplasty dilatation for stenotic dysfunction and angioplasty dilatation combined with thromboaspiration for thrombosed segments have comparable technical success rates and short-term patency. Angioplasty dilatation along with primary stenting for central venous stenosis has excellent technical success and notable short-term patency.