Predictors of primary patency after percutaneous balloon angioplasty for stenosis of Brescia-Cimino hemodialysis arteriovenous fistula

Abstract

Objective:

Percutaneous transluminal balloon angioplasty (PTA) is recommended as the first choice to treat stenosis of Brescia-Cimino arteriovenous fistulas (B-C AVFs). The ability to predict which B-C AVFs are at risk for recurrent stenosis post-PTA would allow closer monitoring of patients, and possibly result in surgical intervention rather than repeat PTA. The purpose of this study was to identify predictive factors of primary patency after PTA in B-C AVFs.

Methods:

Patients diagnosed with B-C AVF primary stenosis and treated by PTA between November 2013 and March 2018 were included in the study. Patient and stenotic lesion characteristics and PTA procedure factors were included in the analysis. The Kaplan–Meier method was used to analyze the primary patency rate. Cox proportional hazard regression analysis was used to identify factors predictive of decreased primary patency.

Results:

74 patients (35 males, 39 females) with a mean age of 61.68 ± 11.44 years (range, 36–84 years) were included in the study. The mean B-C AVF age was 16.34 ± 12.93 months (range, 2–84 months), and the median primary patency time was 7.79 ± 0.48 months. Cox proportional hazard regression analysis revealed stenosis location at the inflow artery [hazard ratio (HR)=3.83, 95% confidence interval (CI): 1.46–10.09] or anastomosis (HR = 1.90, 95% CI: 1.09–3.32), dilation >2 times during PTA (HR = 2.30, 95% CI: 1.22–4.34), and residual stenosis >30% (HR = 2.42, 95% CI: 1.26–4.63) were significantly associated with decreased patency.

Conclusion:

In conclusion, the primary patency rate of PTA for B-C AVF dysfunction is reduced by dilation >2 times, residual stenosis >30%, and stenosis located at the inflow artery or anastomosis. These results may help in tailoring surveillance programs, multiple PTA, or a proximal re-anastomosis surgery in patients with AVF dysfunction.

Advances in knowledge:

A number of studies have been conducted to examine the predictors of primary patency after PTA, however, no definitive conclusions have been reached. Our study revealed that stenosis location at the inflow artery or anastomosis, dilation >2 times during PTA, and residual stenosis >30% were the predictors of primary patency after PTA, which may help in tailoring surveillance programs, multiple PTA, or a proximal re-anastomosis surgery in patients with arteriovenous fistulas dysfunction.

Introduction

Brescia-Cimino arteriovenous fistulas (B-C AVFs) are regarded as the first choice for hemodialysis access due to their convenience, lower complication rates, and superior longevity.¹ However, hemodynamically significant stenosis and ultimately thrombosis are the most frequent causes of access dysfunction.^2–4 Percutaneous transluminal balloon angioplasty (PTA) is recommended for the treatment of stenosis ≥50% by the Kidney Disease Outcomes Quality Initiative clinical practice guidelines because the procedure has a high success rate and is minimally invasive.⁵ Despite proven advantages of PTA in B-C AVF stenosis, the 12 month patency rate ranges between 26 and 62%.^3,6–10 To maintain patency of B-C AVFs, repeated interventions are required. As such, the cost of repetitive PTA becomes a big financial burden for the end-stage renal disease (ESRD) population. Thus, new methods to reduce the frequency of PTA and improve the primary patency rate are needed. The ability to predict which B-C AVFs are at risk for recurrent stenosis post-PTA would help to define those patients that require rigorous monitoring and plan for re-PTA or possibly open surgery in a timely manner.^11–15

A number of studies have examined predictors of primary patency after PTA.^{1–3,6,8,10–16} However, despite the number of studies performed examining the issue, no definitive conclusions have been reached. Some studies have examined technical factors, while other clinical factors. Not unexpected, Sidhu et al¹² reported that technical failure of PTA was associated with lower primary patency rates. Older age, longer lesion length, and younger fistula have been reported to be associated with lower primary patency rates in some studies.^6,10,11,16 On the other hand, early studies have reported that higher age was the only factor associated with lower primary patency,⁷ and that no clinical factors were associated with the primary patency rate after PTA.¹⁷ A 2014 systematic review by Neuen et al¹⁸ included 11 non-randomized observational studies and 965 fistulas. The authors concluded that the overall study quality was suboptimal, and that only younger age and longer lesion length were associated with decreased primary patency after PTA.

Thus, the purpose of this study was to comprehensively analyze patient clinical factors, lesion characteristics, and PTA procedural factors to identify those associated with a significantly lower primary patency rate after PTA. Clarification of these factors can help determine which patient should have more frequent monitoring and evaluation, and those that may benefit from surgery rather than PTA.

Methods

Patients

The Research Ethics Committee of the First People’s Hospital of FoShan approved this study, and all patients provided informed written consent for study participation and all procedures performed.

Between November 2013 and March 2018, consecutive hemodialysis patients with stenosis of B-C AVFs were recruited for enrollment in the study. All the B-C AVFs were mature, functioning, and without any prior previous surgical or endovascular repair procedure.

Data acquisition

The data acquisition was performed based on Doppler ultrasound findings in the “pre-operative examinations” and “post-operative follow-up” by two independent ultrasound physicians, including the access luminal diameter, access flow, peak flow rate, and restenosis. Clinical fistula stenosis was defined according to standard characteristics as follows. (1) Attenuation or absence of a clinically detectable thrill or bruit. (2) Absolute access flow decreased to <350 mL/min, or a decrease of 25% or greater compared to baseline blood flow on at least two separate evaluations by the sonographic dilution method (GE LOGIQ E9, Boston, USA).^3,5,12,13 (3) Access luminal diameter narrowed ≥50% compared with the adjacent normal vessel.^5,19 Fistulous recirculation volume >5% evaluated by sonographic dilution. (5) Dynamic venous pressure exceeded the threshold level on three consecutive measurements.^3,12 (6) Difficult cannulation. (7) Edema of the fore extremity or visible abnormal collateral vessels. (8) Prolonged bleeding from puncture sites.³

Patients with at least one of the aforementioned criteria received fistulography, and subsequent treatment with PTA. Patients with short lesion occlusion/thrombosis identified within 48 h that were treated only by PTA were included. Thrombosed B-C AVFs requiring thrombolysis, or endovascular thrombus aspiration, or surgical thrombectomy before PTA were excluded. In addition, females who were pregnant and patients <18 years of age were excluded.

Endovascular treatment

All PTA procedures were initiated with puncture of the brachial artery after local anesthesia. After heparinization (2000–3000 units), a 5F sheath (Terumo, Tokyo, Japan) was inserted and digital subtraction angiography (DSA) was performed to visualize the stenosis. After confirmation of ≥50% stenosis or short occlusion/thrombosis, balloons 4–6 mm in diameter were inserted and inflated a 0.035 inches guidewire (Terumo, Tokyo, Japan). If necessary, a second puncture of the outflow vein in the direction of the stenosis was performed when the guidewire or balloon could not be passed through the stenotic/occlusive lesion from the brachial sheath.

The balloon size chosen was 0–1 mm larger than the adjacent non-stenotic vessel. When balloons were inflated, the inflation was maintained for 3 min. When a plain balloon (Pacific, Medtronic, Minneapolis, USA) was used, the inflation pressure was 6–10 atmospheres. When a high-pressure balloon (Mustang, Boston Scientific, Marlborough, USA; Armada, Abbott, Chicago, USA) was used, the inflation pressure was 16–24 atmospheres. When dilation-resistant or early elastic recoil lesions were encountered, dilation was repeated 3–5 times. After dilatations, post-PTA fistulography was performed to evaluate the degree of stenosis. Finally, the sheath was removed and hemostasis was achieved by manual compression.

Study endpoints and definitions

The technical success of PTA was defined as residual stenosis <30%. Clinical success was defined as the resolution of clinical access malfunction, and at least one adequate hemodialysis procedure after PTA.^13,20 Primary patency was defined as the time period after PTA until the occurrence of restenosis ≥50%, thrombosis, repeated intervention, abandonment of AVF use, or the end of follow-up.⁵ Post-PTA, ultrasonography was performed every 3 months to evaluate the degree of stenosis. Ultrasonography was also performed if there was any clinical evidence of significant restenosis.

Complications were classified as minor or major according to guidelines of the Society of Cardiovascular and Interventional Radiology.²¹

Clinical variables evaluate were patient age and sex, AVF age, AVF side (left or right), dialysis frequency (≤2 times/week, >2 times/week), the use of antiplatelet therapy, and cause of ESRD: diabetes mellitus (DM), nefroangiosclerosis, glomerular disease, autosomal dominant polycystic kidney disease (ADPKD), tubulointerstitial, and unknown. Comorbidities included in the analysis were coronary heart disease (CHD), DM, valvular heart disease (VHD), and hypertension (HTN).

Evaluation of outcome parameters

Outcome parameters were measured and evaluated by two independent vascular surgeons. Anatomical variables evaluated were lesion position, lesion length (≤2 cm, >2 cm), degree of stenosis, and number of stenotic areas (single or multiple). With respect to the location of the stenosis, the AVF in the forearm section was divided into five segments: the feeding artery, the arteriovenous anastomosis, juxta-anastomosis vein (within the first 5 cm of the cephalic vein from anastomosis),¹⁴ forearm outflow vein, and elbow vein. Dysfunctional fistulas resulting from upper arm or central venous stenosis/occlusion were excluded in this study. Stenosis grade was defined as mild (50–75%), moderate (75–90%), severe (>90%), and complete occlusion.¹¹

PTA variables examined were balloon type (plain balloon, high-pressure balloon), incremental dilation, number of dilatations (≤2, >2), final balloon diameter (4, 5, or 6 mm), and residual stenosis (<30%, ≥30%).

Statistical analysis

Continuous variables were expressed as mean ± standard deviation (SD) and range (minimum to maximum). Categorical variables were presented as number and percentage. The patency rate was estimated using the Kaplan–Meier method. Cox proportional hazard regression analysis was used to analyze the effects of independent variables on the primary patency rate, and results were reported as hazard ratio (HR) and 95% confidence interval (CI). Box-and-whisker plot was then used to describe the distribution of primary patency time of associated categorical variables. All analyses were performed using IBM SPSS v. 20 software (SPSS Statistics v20, IBM Corporation, Somers, New York). Values of p ≤ 0.05 were considered to indicate statistical significance.

Results

Patient demographic and clinical characteristics

A total of 74 patients, 35 males (47.3%) and 39 females (52.7%), were included in the study. Patient characteristics are summarized in Table 1. The mean patient age was 61.68 ± 11.44 years (range, 36–84 years), and the mean B-C AVF age was 16.34 ± 12.93 months (range, 2–84 months). There are 55 AVF on the left side (74.3%), and 19 cases on the right side (25.7%). In approximately one-third of the patients, ESRD was due to DM (n = 25, 33.8%) (Table 1). Comorbidities included CHD (n = 16, 21.6%), DM (n = 23, 31.1%), VHD (n = 9, 12.2%), and HTN (n = 38, 51.4%). 24 (32.4%) of the patients received dialysis ≤2 times per week, and 50 patients (67.6%) received dialysis >2 times per week. Approximately, half of the patients (n = 42, 56.8%) were receiving antiplatelet therapy.

Table 1.

Patient characteristics (N = 74)

Patient age (year)	61.68 ± 11.44	36–84
Sex
Male	35	47.3
Female	39	52.7
AVF age (month)	16.34 ± 12.93	2–84
AVF side
Left	55	74.3
Right	19	25.7
Cause of ESRD
DM	25	33.8
Nefroangiosclerosis	16	21.6
Glomerular disease	17	23
ADPKD	6	8.1
Tubulointerstitial	9	12.2
Unknown	9	12.2
Comorbidities
CHD	16	21.6
DM	23	31.1
VHD	9	12.2
HTN	38	51.4
Dialysis frequency (/week)
≤2	24	32.4
>2	50	67.6
Antiplatelet therapy
Yes	42	56.8
No	32	43.2

ESRD, end-stage renal disease; DM, diabetes mellitus; ADKPD, autosomal dominant polycystic kidney disease; CHD, coronary heart disease; VHD, valvular heart disease; HTN, hypertension.

Patient age and AVF age are presented as mean ± standard deviation and range; other data are presented as number and percentage.

Lesion anatomical characteristics

The lesion anatomical characteristics are summarized in Table 2. Fistulography revealed that the stenosis was located in the feeding artery in 6 patients (8.1%), in the arteriovenous anastomosis in 22 patients (29.7%), in the juxta-anastomosis vein in 66 patients (89.2%), in the outflow vein in 14 patients, and in the elbow vein in three patients. The length of the stenosis was ≤2 cm in 23 patients (31.5%), and >2 cm in 50 patients (68.5%). Moderate stenosis was the most common, present in 33 patients (44.6%). 21 patients had severe stenosis (28.4%) and 9 (12.2%) had complete occlusion. 34 patients (45.9%) had single areas of stenosis, while the other 40 patients (54.1%) had ≥2 areas of stenosis.

Table 2.

Stenotic lesion anatomical characteristics

Position
Inflow artery	6	8.1
Anastomosis	22	29.7
Juxta-anastomosis	66	89.2
Outflow vein	14	18.9
Elbow vein	3	4.1
Length (cm)
≤2	24	32.4
>2	50	67.6
Stenosis grade (%)
≥50 and<75	11	14.9
≥75 and<90	33	44.6
≥90 and<100	21	28.4
Complete occlusion	9	12.2
Numbers of stenosis
1	34	45.9
≥2	40	54.1

Data are presented as number and percentage.

PTA characteristics

The characteristics of the PTA procedures are summarized in Table 3. A plain balloon was used in 31 cases (41.9%), and a high-pressure balloon was used in the 43 cases (58.1%). 19 procedures (25.7%) were performed with incremental dilation (a larger balloon was used after initial dilatation with a smaller balloon, e.g., 4 to 5 mm or 6 mm). In 32 patients, the largest balloon diameter used was 4 mm, in another 32 cases the largest balloon diameter used was 5 mm, and in 10 cases the largest balloon diameter used was 6 mm. Dilatation was performed ≤2 times in 34 cases (45.9%), and >2 times in 40 cases (54.1%).

Table 3.

PTA characteristics

Balloon type
Plain	31	41.9
High pressure	43	58.1
Incremental dilation
Yes	19	25.7
No	55	74.3
Dilation times
≤2	34	45.9
>2	40	54.1
Final balloon diameter (mm)
4	32	43.2
5	32	43.2
6	10	13.5
Residual stenosis (>30%)
No	41	55.4
Yes	33	44.6

PTA, percutaneous transluminal balloon angioplasty.

Data are presented as number and percentage.

Technical success, clinical success, complication, and primary patency

PTA was technically successfully in 55.4% of patients (n = 41). The degree of residual stenosis was >30% but <50% in 33 patients (44.6%). Clinical success was achieved in all patients. No major complication occurred in any patient. Hematoma at the puncture site (minor complication) occurred in five patients (4.4%). The median primary patency time was 7.79 ± 0.48 months (Figure 1). After PTA, the B-C AVF remained patent in only six patients (8.1%) during the entire follow-up. The pre-operative ultrasound, intraoperative angiography and post-PTA ultrasound images of a representative case of a 48-year-old female patient with post-PTA restenosis were shown in Figure 2.

Figure 1.

Kaplan–Meier curve for primary patency of B-C AVF stenosis treated by PTA. B-C AVF, Brescia-Cimino arteriovenous fistula; PTA, percutaneous transluminal balloon angioplasty.

Figure 2.

The pre-operative ultrasound, intraoperative angiography and post-PTA ultrasound images of a 48-year-old female patient were shown. (A) Pre-operative ultrasound showed severe stenosis of the left B-C AVF, with the narrowest diameter of 0.14 cm. (B) The left brachial artery angiography showed severe stenosis in the anastomotic site and multiple segments of the cephalic vein. (C) A balloon (5 × 120 mm) was used to dilate the narrow segment vessels. (D) Post-PTA angiography showed residual stenosis <30%. (E). Follow-up ultrasound at 2 days post-PTA showed that the diameter of the original stenosis was 0.35 cm. (F). Ultrasound image at 3 month follow-up showed that the diameter of the original stenosis was 0.30 cm. (G) Ultrasound image at 6 month follow-up showed restenosis of the anastomotic site, and the diameter of the stenosis was 0.15 cm. B-CAVF, Brescia-Cimino arteriovenous fistula; PTA, percutaneous transluminal balloonangioplasty.

Cox proportional hazard regression analysis for prognostic factors

The results of the multivariate Cox regression analysis are presented in Table 4. The analysis revealed that stenosis at the inflow artery (HR = 3.83, 95% CI: 1.46–10.09; p = 0.007), stenosis at the anastomosis (HR = 1.90, 95% CI: 1.09–3.32; p = 0.023), >2 dilatations during PTA (HR = 2.30, 95% CI: 1.22–4.34; p = 0.010), and residual stenosis >30% (HR = 2.42, 95% CI: 1.26–4.63; p = 0.008) were significant predictors of reduced primary patency after PTA.

Table 4.

Cox proportional hazards analysis for post-PTA primary patency

Variables	Univariate analysis		Multivariate analysis
	HR (95% CI) p-value		HR (95% CI) p-value
Patient age (year)
≤60	Reference	-
>60	1.480 (0.908–2.412)	0.116
AVF age (month)
≤12	Reference	-
>12	0.665 (0.407–1.088)	0.104
Sex
Male	Reference	-
Female	1.038 (0.644–1.674)	0.879
AVF side
Left	Reference	-
Right	1.045 (0.605–1.804)	0.875
Cause of ESRD
DM	1.117 (0.666–1.873)	0.675
Nefroangiosclerosis	1.604 (0.899–2.861)	0.11
Glomerular Disease	0.649 (0.355–1.185)	0.159
ADPKD	1.030 (0.618–1.716)	0.91
Tubulointerstitial	0.913 (0.629–1.325)	0.631
Unknown	1.081 (0.758–1.542)	0.667
Comorbidity
CHD	1.187 (0.894–1.576)	0.235
DM	1.012 (0.777–1.318)	0.93
VHD	0.999 (0.698–1.431)	0.995
HTN	1.093 (0.854–1.399)	0.482
Dialysis frequency (/week)
≤2	Reference	-
>2	0.752 (0.443–1.275)	0.29
Antiplatelet therapy
Yes	Reference	-
No	1.329 (0.819–2.157)	0.25
Stenosis location
Inflow artery
Anastomosis	2.038 (1.291–3.216)	0.002	3.833 (1.456–10.087)	0.007
Juxta-anastomosis	1.378 (1.064–1.786)	0.015	1.904 (1.094–3.315)	0.023
Outflow vein	0.928 (0.636–1.354)	0.698
Elbow vein	0.893 (0.662–1.204)	0.458
Stenosis length (cm)	0.866 (0.484–1.549)	0.627
≤2
>2	Reference	-
Stenosis grade (%)	1.201 (0.715–2.018)	0.489
≥50 and<75		0.18
≥75 and<90	Reference	-
≥90 and<100	1.501 (0.717–3.141)	0.281
Occlusion	1.272 (0.587–2.756)	0.541
Numbers of stenotic areas	2.829 (1.076–7.434)	0.035
1	Reference	-
≥2	1.505 (0.927–2.444)	0.098
Balloon type
Plain	Reference	-
High pressure	1.216 (0.740–1.998)	0.439
Incremental dilation
Yes	Reference	-
No	1.662 (0.928–2.977)	0.088
Dilation times
≤2	Reference	-	Reference	-
>2	3.155 (1.865–5.337)	<0.001	2.304 (1.223–4.340)	0.01
Final balloon diameter (mm)		0.004
4	Reference	-	Reference	-
5	0.444 (0.258–0.766)	0.004	0.687 (0.378–1.248)	0.218
6	0.353 (0.164–0.759)	0.008	0.438 (0.180–1.065)	0.069
Residual stenosis (>30%)
No	Reference	-	Reference	-
Yes	2.609 (1.573–4.328)	<0.001	2.419 (1.2630–4.632)	0.008

ADKPD, autosomal dominant polycystic kidney disease; CHD, coronary heart disease; CI, confidence interval; DM, diabetes mellitus; ESRD, end-stage renal disease;HR, hazard ratio; HTN, hypertension;PTA, percutaneous transluminal balloon angioplasty; VHD, valvular heart disease.

A balloon diameter of 5 mm or 6 mm was associated with an increased primary patency rate in univariate analysis but was not a significant predictor in the multivariate analysis. The box-and-whisker plot for subgroup analyses of the primary patency time in patients stratified by these prognostic factors were shown in Figure 3.

Figure 3.

The box-and-whisker plot for subgroup analyses of the primary patency time in patients stratified by the prognostic factors identified by the multivariate Cox-regression, including artery (A), anastomosis (B), didlation times (C), and residual stenosis (D).

Discussion

In the present study, we analyzed predictors of primary patency in patients with stenosis of B-C AVF undergoing PTA for the first time. We found that dilation >2 times during PTA, residual stenosis >30%, and stenosis located at the inflow artery or anastomosis were predictors of restenosis. The ability to predict subsequent B-C AVF failure after initial PTA is important. We would therefore advocate these patients should receive more frequent monitoring, or possibly proximal re-anastomosis surgery of the cephalic vein to the radial artery a few centimeters above the stenotic venous segment.¹⁴

We observed a technical success rate of 55.4%, which is lower than the rate of 75–97% reported in prior studies.^3,6,7 However, our mean primary patency time was comparable to that reported by Tessitori et al²² (7.79 vs 8 months), but shorter than that reported in other studies.¹⁴ A recent study by Aktas et al⁶ of 330 stenoses in 228 patients reported a technical success rate of 96% and a clinical success rate of 97%. Older age and DM were associated with early dysfunction and a lower primary patency rate. In addition, age and DM, along with the length of stenosis early recurrence, and residual stenosis were associated with a lower secondary patency rate. Furthermore, PTA technical failure has been shown to significantly affect the primary patency rate.¹² We suspect that the difference in results may be due to our conservative balloon size selection (the balloon size was 0–1 mm larger than the adjacent non-stenotic vessel), and the greater use of plain balloons (41.9%) rather than high-pressure balloons. Furthermore, Romann et al¹¹ reported that Asians were more likely to undergo multiple PTA for restenosis.

We identified that stenosis located at the inflow artery or anastomosis were adverse prognostic factors. It is possible that the small size of the balloons used is responsible for this finding, although balloon size was not statistically significant in multivariate Cox analysis. Different from venous neointimal hyperplasia, the pathological characteristics of inflow vessel stenosis is atherosclerosis.¹⁸ PTA has been shown to be less effective when used to treat stenosis in the forearm artery or juxta-anastomotic stenosis.^14,23,24 These findings suggest that treatment of anastomotic stenosis should be surgical rather than endovascular. While a number of studies have examined the effect of lesion location on primary patency, their results have not been consistent.^11,14,18,19 Romann et al¹¹ reported that outflow vein stenosis, in addition to stenosis >2 cm, was associated with requiring a second PTA. While we did not specifically study lesion morphology, Suemitsu et al¹³ reported that a shrinking lumen was associated with a lower primary patency rate, while venous-valve-related stenosis was associated with a higher primary patency rate. The authors also found that lower flow volume and prior PTA were associated with lower primary patency.

Our finding that dilation >2 times during PTA and residual stenosis >30% were adverse prognostic factors is consistent with other studies that found residual stenosis >30% impacted overall access patency.^3,12 However, other authors have reported no significant association between residual stenosis >30% and 12 month primary access patency in AVFs following PTA.^6,16 The recent report by Atkas et al⁶ in which clinical success was achieved in 97% of 330 stenoses found residual stenosis following PTA impacted secondary, but not primary patency. While a cutoff of residual stenosis of 30% or less is a well-accepted target, achieving residual stenosis of much less than 30% is likely possible by performing a greater number of dilatations during PTA, increasing the expansion force (e.g. ultra-high pressure balloon), and/or prolonging the balloon inflation time. However, these methods would theoretically produce greater vessel trauma, and the effect of greater vessel trauma on post-intervention access circuit patency is not known. Elramah et al² and Forauer et al²⁵ reported longer inflation time may have a negative impact on patency. Thus, further investigation of these methods and achieving residual stenosis much less than 30% require investigation. Although not examined in this study, the use of a cutting balloon has been shown to be safe, and provide higher patency rates than standard PTA, especially when the residual stenosis with conventional PTA is >30%.^26–28

Interestingly, final balloon size was a significant prognosis factor in Cox univariate analysis, but not in multivariate analysis. Intuitively, one would expect that a larger balloon size would result in greater dilatation and lower residual stenosis. However, as previously mentioned we used a very conservative balloon size (the balloon size was 0–1 mm larger than the adjacent non-stenotic vessel) in our procedures.

A number of variables, including patient age, AVF age, DM, stenosis length, and stenosis grade were not associated with the primary patency rate in our analysis. However, various studies have found associations of these factors with the primary patency rate.^{3,6,7,10,11,16} And, it should be mentioned that the findings across the prior studies were not consistent (i.e. studies did not always find the same factors significant). As Neuen et al¹⁸ pointed out in their systematic review of 11 studies, the quality of studies examining this topic is suboptimal. This, along with other variables such as patient population, surgical technique, and definitions of endpoints may account for the different findings between studies.

There are still some limitations to this study. This study was limited by its relatively small sample size. In addition, we did not use different PTA techniques to examine patients, and lesions, such as transarterial and transvenous PTA²⁹ and drug-coated PTA.³⁰ All these limitations should be addressed in future studies.

Conclusions

This study suggested that predictive factors of primary patency after PTA in B-C AVFs included dilation >2 times during PTA, residual stenosis >30%, and stenosis located at the inflow artery or anastomosis. Patients with these findings should receive closer surveillance of AVF patency, or a proximal re-anastomosis surgery should be considered.