Anatomical Feasibility of Percutaneous Arteriovenous Fistula Formation in Korea

Abstract

Introduction

Currently, there are two types of percutaneous arteriovenous fistula (pAVF) formation systems approved by the FDA: Ellipsys and WavelinQ. Although these systems are already in use in Europe or the United States, they have not been approved for use in Korea yet. For this reason, this study aimed to check anatomical feasibility of these systems for Korean population prior to their actual use.

Methods

Consecutive patients who received ultrasound vein mapping for arteriovenous fistula formation from June 2021 to June 2022 were included. The anatomical feasibility of each system was confirmed according to the manufacturer’s instructions for use (IFU).

Results

Upper extremity ultrasonography was performed for a total of 83 patients to determine their feasibility for pAVF formation. Of these patients, 65.1% were feasible for pAVF formation with appropriate deep communicating vein (DCV) and outflow. Among them, 57.8% were feasible for the Ellipsys system and 54.2% were feasible for the WavelinQ system. Most patients who were infeasible for pAVF formation had a DCV of small size. Ulnar vessels were more suitable than radial vessel for WavelinQ (54.2% vs 33.7%, P-value = .012). The most common reason for not meeting the criteria was a small vein size at the access site.

Conclusions

More than half of all patients were feasible for pAVF formation in this study. Ellipsys had a higher feasibility than WavelinQ, although they showed no significant difference in the feasibility. If these devices are imported into Korea, it will be a good opportunity for many patients to reduce the surgical burden and create AVFs more easily through these procedures.

Keywords

arteriovenous fistula vascular access devices dialysis access anatomy

Introduction

End-stage renal failure (ESRD) is one of the diseases with a continuous increase in incidence worldwide.^1,2 Creation of permanent hemodialysis access is an essential procedure for ESRD patients. According to The National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF KDOQI) clinical practice guidelines, an arteriovenous fistula (AVF) rather than an arteriovenous graft (AVG) is recommended and that it should be made as distal as possible.³ High rate of long-term patency and low complication rate are great advantages of AVF. However, the lack of superficial veins with adequate size at distal arms or low maturation rate remains its major problem.^4,5

With recent rapid development of percutaneous procedures in vascular surgery, new endovascular devices for AVF formation have emerged. FDA-approved Ellipsys vascular access system (Avenu Medical, san Juan Capistrano, CA, USA) and WavelinQ endo AVF system (Bard Peripheral Vascular, Tempe, AZ, USA) are currently being used in Europe and USA. Many studies have reported their outcomes.^6-11 In both systems, the superficial vein of the upper arm matures through the deep communicating vein (DCV). However, they show differences in vessels used and method of making anastomosis. Ellipsys is a single venous catheter system that percutaneously creates a vascular anastomosis with DCV and radial artery using direct current thermal heating energy. This system creates a fistula by puncturing directly through the DCV to the radial artery.¹² WavelinQ is a dual catheter system that creates an anastomosis between radial artery and radial vein (or ulnar artery and ulnar vein) at proximal forearm by radiofrequency energy. This system punctures the artery and vein respectively, inserts the catheter, magnetically attaches the artery and vein to the location where AVF is to be created, and creates a fistula with radiofrequency energy.¹²

These percutaneous AVF (pAVF) devices have not been yet imported into Korea. However, they will be used eventually in the future. To use these devices, certain anatomic criteria must be satisfied. Most studies related to this have been conducted on Americans or Europeans. The anatomy of the upper arm might differ between Caucasians and Asians. Thus, the aim of this study was to determine the proportion of Koreans anatomically suitable for pAVF formation.

Methods

Selection of Patients

All patients who received ultrasound vein mapping for AVF formation from June 2021 to June 2022 at the Seoul St. Mary’s Hospital were included. Most of these patients were chronic kidney disease (CKD) stage 4 or 5 patients who needed dialysis in the near future or were already undergoing dialysis using a central venous catheter. Some of them had an AVF but planned to create a new one due to maturation failure, infection, or obstruction. Since the examination was for AVF formation surgery, vein mappings were preferentially performed for the patients’ non-dominant arm. However, when the patient had no usable vein in the non-dominant arm or could not use that arm due to graft infection, the exam was performed for the dominant arm. This study was approved by the institutional review board of Seoul St. Mary’s Hospital (IRB number: KC23RASI0135).

Vessel Mapping Protocol

All patients were tested in the supine position in a room temperature environment. Linear probe with a frequency range of 4-15 MHz was used for examination. Tourniquet was not used. The examination was performed from the distal arm to the proximal direction. All vessels were observed by transverse view and longitudinal view in B-mode. Horizontal and vertical diameters of vessels were measured at the point where the cross-section looked as round as possible. In addition, compression was avoided as much as possible when measuring the length. When there was a difference between the horizontal length and the vertical length, the shortest length was determined as the size of the vessel. The distance between two vessels was measured as the shortest distance in a straight line (Figure 1). If there is a thrombus or obstruction in the vessel, it was regarded as an unusable vessel and the diameter was not measured.

Anatomical Criteria for Percutaneous AVF

Regardless of the device, patients who had DCV with an adequate size (DCV diameter ≥ 2 mm) and an adequate outflow vein (upper arm cephalic vein and/or basilic vein diameter ≥ 2.5 mm) were considered as candidates for pAVF.

Anatomical Criteria for Ellipsys

Based on the instruction for use (IFU), it was considered feasible for pAVF procedure with the Ellipsys system when the size of the proximal forearm radial artery was greater than 2 mm and the distance between the DCV and radial artery was less than 1.5 mm.

Anatomical Criteria for WavelinQ

Based on the IFU, it was considered feasible for pAVF procedure with the WavelinQ system when the size of the proximal forearm radial artery/vein or ulnar artery/vein was greater than 2 mm. WavelinQ system requires a separate access site to reach the target vessel for anastomosis. Therefore, arteries and veins greater than 2 mm must be present in the brachial artery/vein at upper, radial artery/vein of wrist or ulnar artery/vein of wrist.

Results

Upper extremity ultrasonography was performed in a total of 83 patients during the study period. The mean age of these patients was 64.3 years. There were 48 (57.8%) males and 35 (42.2%) females. Of these 83 patients, 77 (92.8%) had hypertension and 45 (54.2%) had diabetes mellitus as an underlying disease. Among them, only five had previously arteriovenous fistula surgery on the same side arm where the ultrasonography was performed. All others had ultrasound vein mapping for the first time. Since right-handed people were common and the non-dominant arm was mainly tested, 74 (89.2%) and 9 (10.8%) patients had examination on the left arm and right arm, respectively (Table 1).

Table 1.

Baseline Characteristics of Study Patients.

Characteristics	Value
Total	83 (100%)
Age (years)	64.3 ± 14.0
Gender
Male	48 (57.8%)
Female	35 (42.2%)
Comorbidity
Hypertension	77 (92.8%)
Diabetes mellitus	45 (54.2%)
Previous arteriovenous fistula formation	5 (6.0%)
Mapping side
Left	74 (89.2%)
Right	9 (10.8%)

The mean diameter of the upper arm outflow was larger with the basilic vein (3.7 mm) than with the cephalic vein (2.9 mm). DCV was present in 71 (85.5%) patients. The mean DCV diameter was 2.2 mm. At forearm proximal, ulnar artery and vein were larger than radial artery and vein on average and the distance between the artery and vein was less than 1 mm for radial and ulnar one similarly. The vessel diameter of access site for WavelinQ was measured for upper arm brachial, wrist radial, and wrist ulnar vessels. The mean diameter was the largest for the brachial vessel (artery: 4.6 mm, vein: 3.3 mm) and the smallest for the ulnar vessel (artery: 1.7 mm, vein: 1 mm) (Table 2).

Table 2.

The Diameter of the Upper Extremity Vessels for Creating pAVF.

Anatomical Characteristics	Mean ± SD (MM)
DCV
DCV presence	71 (85.5%)
DCV diameter	2.2 ± 1.2
Outflow
Cephalic vein diameter	2.9 ± 1.3
Basilic vein diameter	3.7 ± 1.4
Ellipsys
Radial artery diameter	2.5 ± 1.2
Radial artery – DCV distance	1.0 ± 1.0
WavelinQ
Radial artery diameter	2.6 ± 0.7
Radial vein diameter	1.9 ± 0.5
Ulnar artery diameter	3.5 ± 0.9
Ulnar vein diameter	3.0 ± 0.9
Access site
Brachial artery diameter	4.6 ± 0.9
Brachial vein diameter	3.3 ± 0.8
Radial artery diameter	2.2 ± 0.6
Radial vein diamter	1.5 ± 0.5
Ulnar artery diamter	1.7 ± 0.6
Ulnar vein diameter	1.0 ± 0.4

Abbreviations: DCV, deep communicating vein; pAVF, percutaneous arteriovenous fistula.

Of 83 patients, 54 (65.1%) were candidates for pAVF formation in our study. There were 29 patients who were unsuitable for this procedure (12 patients who had no DCV and 17 patients who had DCV but the size was less than 2 mm) and 2 patients who had no outflow vessel with an appropriate size.

Forty-eight (57.8%) patients were eligible for the Ellipsys system. Among 54 patients who were candidates for the procedure, six patients could not use Ellipsys system anatomically. The distance between the DCV and the radial artery was greater than 1.5 mm in five patients. There were no patients who were dissatisfied only with the criterion that RA size should be 2 mm or more. Only 1 patient was unable to use Ellipsys due to dissatisfaction with both criteria.

On the other hand, 50 (60.2%) patients were eligible for WavelinQ system. As previously explained, WavelinQ can create AVF using proximal forearm radial vessels (radial artery & vein) or ulnar vessels (ulnar artery & vein). According to this, 50 patients could be classified into two groups: (1) 20 patients who could use only ulnar vessels, and (2) 30 patients who could use radial and ulnar vessels. There were no patients who could only use radial vessels. Twenty-four patients were not feasible for WavelinQ at radial vessels. Of them, 6 did not meet the radial artery diameter criteria and 23 did not meet the radial vein diameter criteria. However, all patients met the criteria for the distance between artery and vein. Of 4 patients for whom WavelinQ was not feasible for ulnar vessels, all failed to meet the ulnar vein diameter criteria and all patients met the ulnar artery criteria. Likewise, all patients satisfied the criteria for the distance between ulnar artery and vein.

WavelinQ must satisfy the procedure access site criteria since the fistula formation site and access site are different. Thus, brachial vessels at upper arm, radial vessel, and ulnar vessel of wrist were examined and 45 (54.2%) of 50 patients satisfied access site criteria. All 45 patients satisfied the criteria for upper arm brachial vessels, 5 patients satisfied with radial vessels at wrist. However, there were no patients who satisfied with ulnar vessels at wrist.

In summary, among a total of 83 patients, 48 patients met the criteria for Ellipsys, while 45 patients met the criteria for WavelinQ. There was no significant difference between the two groups (P-value = .9). When WavelinQ was divided based on the location for creating AVF, radial vessels were available in 28 patients and ulnar vessels were available in 45 patients, with a significant difference observed between the two groups (P-value = .012) (Table 3). An algorithm for determining anatomical eligibility for creating pAVF in all patients is shown in Figure 2.

Table 3.

Comparison of Eligibility According to Devices.

	Eligibility (%)	P-value
Total		0.9
Ellipsys	48 (57.8%)
WavelinQ	45 (54.2%)
WavelinQ		0.012
Radial vessels	28 (33.7%)
Ulnar vessels	45 (54.2%)

Discussion

We compared anatomical feasibility of the two systems for pAVF. In order to confirm the feasibility, we first checked whether there were perforator veins and outflow veins with appropriate sizes before checking the criteria of the two pAVF systems. This is because pAVF is a system that makes fistulas using deep veins at forearm and maturate outflow veins in the upper arm through perforator veins to enable dialysis. Shahverdyan et al¹³ have also shown a detailed classification of perforator vein and outflow flow vein according to the type of AVF and type of using vessels for anastomosis. In this study, 65.1% of all patients satisfied these criteria. The main reason for not satisfying the criteria was either no DCV or a small DCV. There were 15 patients with a small DCV size. Of them, 2/3 satisfied the anatomical criteria of WavelinQ. In other words, if the DCV size was large, wavelinQ could be used. The flow of DCV actually increases, like other veins after AVF is created on the distal arm.¹⁴ Therefore, feasibility of pAVF might be higher in patients who have previously made AVF in the distal arm. However, the impact of previous AV access formation could not be investigated in this study because there were only five patients who underwent duplex examination on the same side of arm with AVF or AVG in the distal arm. Nevertheless, all 3 of the 5 patients had a sufficiently large DCV size. They were feasible for wavelinQ, except for two patients with no DCV at all. Further studies related to this will be needed.

On the other hand, life expectancy of ESRD patients is increasing with the development of medical managent.¹⁵ It means that the dialysis period of these patients is increasing. Since the 1-year secondary patency of AVF is approximately 80%, a longer period of dialysis means an increase in the proportion of patients undergoing multiple hemodialysis access formation.^5,16,17 AVF also has a high maturation failure rate.^4,18 From this point of view, pAVF can be a valuable additional option as an intermediate step for patients with distal arm AVF before moving up to the upper arm.

In this study, 57.8% of all patients were able to use Ellipsys and 54.2% were able to use WavelinQ. These results were similar to those of other studies with a feasibility of about 50-60%.^19-21 In a study of Franco et al.,²¹ Ellipsys was feasible in 63%. Although results did not show a big difference, the feasibility was lower in our study. This might be because we did not apply a tourniquet during examination. Popli et al²⁰ have found that 55% are suitable for wavelinQ and 44% are suitable for Ellipsys. In our study, WavelinQ showed lower feasibility than Ellipsys as opposed to Popli et al. The reason for such a result might be because we checked whether the criteria of the access site were satisfied. Popli et al. only checked the criteria of the pAVF at anastomosis site. In our study, when the access site was not considered, WavelinQ was found to be feasible in 60.2%.

According to results related to WavelinQ, when comparing radial vessels and ulnar vessels, it was confirmed that the ulnar vessels had higher feasibility. (54.2% vs 33.7%). This might be because proximal ulnar vessels are larger in size as they are vessels before the interosseous vessels branch.²² Looking at study results of Berland et al.,²³ pAVF was performed using WavelinQ and ulnar vessels (76.7%) were used much more than radial vessels (23.3%).

This study has several limitations. First, the study design was retrospective, meaning that the data collected might not be as accurate as data collected in a prospective study. Second, the sample size was small. This may reduce the representativeness of the population. Finally, ultrasound results can vary depending on the performer, which might have biased our study results. Nevertheless, the present study has strength as the first study on the anatomical suitability for pAVF in Korea. If these devices are imported into Korea, a significant number of patients will be able to receive help. In addition, in order to increase success rate of the procedure, it is necessary to examine vessels in detail using ultrasound before performing the procedure.

Conclusions

The pAVF is less invasive than surgery. It has various advantages as an additional option, especially for those who have had AV access on distal arm previously. More than half of our patients were feasible to make a pAVF in this study (Ellipsys 57.8%, WavelinQ 54.2%). Therefore, if these devices are imported into Korea, it will be a good opportunity for many patients to reduce the surgical burden and create AVFs more easily through these procedures. Additionally, for patients who plan to undergo this procedure in the future, a more detailed ultrasound examination will need to be performed to accurately identify patients unsuitable for pAVF formation.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Ki Yoon Moon

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