Current ablation treatments for varicose veins can be divided into two types: tumescent and thermal (TT) and nonthermal and nontumescent (NTNT). TT ablation includes laser and radiofrequency treatments. Examples of NTNT ablation include Venaseal^Ⓡ, Clarivein^Ⓡ, and ultrasound-guided sclerotherapy. All treatment methods, excluding sclerotherapy under ultrasonographic guidance, have success rates greater than 90%.

Existing radiofrequency thermal ablation devices adjust the output from the generator to maintain a constant temperature of 120℃. ClosureFast^Ⓡ has a bipolar catheter and is coated with a positive temperature coefficient of resistance (PTCR) to maintain the aforementioned constant temperature. VENISTAR^Ⓡ, a radiofrequency thermal ablation device manufactured in Korea, detects tissue resistance generated during venous ablation and continuously emits radiofrequency waves until a certain resistance threshold is reached. This study aimed to determine the treatment success rate and complications associated with VENISTAR^Ⓡ.

1) Patients

A total of 60 patients with varicose veins who were treated at our institution using VENISTAR^Ⓡ from January, 2021 to September, 2022 were retrospectively analyzed. All patients underwent preoperative ultrasonography. The clinical severity of varicose veins was evaluated using the clinical, etiologic, anatomic, and pathophysiological (CEAP) classification system, and postoperative evaluation was conducted using the venous clinical severity score (VCSS).

Vascular ultrasonography was performed on the patients in a standing position. The diameter of the great saphenous vein (GSV) was measured 2 cm below the saphenofemoral junction (SFJ), midthigh, lower thigh, and below-knee GSV (BK GSV). The diameters of the small saphenous veins (SSVs) were measured in the popliteal fossa, midcalf, and lower calf. Valve insufficiency was defined as reflux lasting for more than 0.5 s during distal compression. This study was approved by the Public Institutional Research and Ethics Committee (P01-202301-01-036) and adhered to the regulations outlined in the Declaration of Helsinki. The requirement for informed consent was waived due to the retrospective nature of the study.

2) Operative methods

Vascular ultrasonography was performed preoperatively for mapping. In the GSV, anesthesia was induced with a femoral nerve block and tumescent local anesthesia; in the SSV, anesthesia was induced with tumescent local anes-thesia. The VENISTAR^Ⓡ catheter consisted of two parts: a radiofrequency output catheter and a cooling system connected to the inside of the catheter. The catheter was wrapped with 7 cm long bipolar electrodes, and the cooling system was connected to a cold saline solution. After connecting to a circulation pump, cold saline was circulated inside the catheter to prevent overheating (Fig. 1).

Figure 1. Generator and circulating pump.

Cold saline was connected to the cooling system and circulation pump, and the catheter was connected to the generator (Fig. 2). Subsequently, the circulation pump was started, and the catheter was used after the temperature dropped below 17℃. Above the knee, the premarked site was incised and punctured using an 18 G puncture needle. Then, a VENISTAR^Ⓡ catheter was inserted using a Terumo 7 F angiocatheter. Under ultrasonographic guidance, the catheter was placed 2 cm below the SFJ or SPJ. The VENISTAR^Ⓡ catheter has an aiming beam at the tip to facilitate the location of the target site (Fig. 3). After injecting a sufficient amount of tumescent solution around the target vein, the circulation pump was initiated. When the temperature of the catheter dropped below 17℃, VENISTAR^Ⓡ radiofrequency thermal ablation device was started by pressing the switch on the handle. After 30 W of radiofrequency was generated in the first 20 s, the radiofrequency output was increased by 1 W every 2 s up to 38 W. In most cases, the first segment reached the resistance threshold between 60 and 90 s, and the radiofrequency output automatically stopped. The catheter was then moved 7 cm posteriorly for a second ablation. Segmental ablation was conducted in the same way as using ClosureFast^Ⓡ. The ablation time was shortened during the second ablation period. After ablation, the BK GSV and protruding varicose veins were treated using ambulatory phlebectomy (AMP) or endovenous laser treatment (EVLT). After compression dressing, each patient was transferred to the ward. Upon discharge, the patient underwent bleeding and paresthesia assessments and wore class 2 compression stockings.

Figure 2. VENISTAR^Ⓡ catheter.

Figure 3. Aiming beam on catheter tip.

3) Follow-up examination

The patients were followed-up at 1 week, 2 weeks, 1 month, 3 months, 6 months, and 1 year after surgery. The VCSS was used for postoperative evaluation, and the size and obstruction of the saphenous veins were assessed using ultrasound. Statistical analyses were performed using Microsoft Excel (Microsoft^Ⓡ), and the cumulative closure rate was used for Kaplan–Meier estimation analysis.

In this study, 60 patients (41 men and 19 women) were treated with VENISTAR^Ⓡ. The mean age was 46.2±11.7 years for men and 52.7±14.2 years for women. The mean body mass index was 26.3±5.1 for men and 23.07±2.0 for women. The CEAP classifications were as follows: 28, 26, 4, and 2 patients had C2, C3, C4a, and C4c diseases, respectively. A total of 89 blood vessels were treated, including 79 involving the GSV and 10 involving the SSV (Table 1). The diameter of the treated vessels was 8.4±1.6 cm for the GSV and 8.5±1.9 cm for the SSV. The mean diameter of the GSV 2 cm below SFJ was 9.8±2.2 cm, and the mean diameter of the SSV at the popliteal fossa was 10.7±3.6 cm. The mean ablation times for the first, second, third, and fourth segments were 53+12.8, 40+9, 35+6, and 30+9 s, respectively. The number of ablation segments varies depending on the length of the vein to be treated, usually 3~4 for the GSV and 1~2 for the SSV. The mean follow-up period was 190±130 days, and the success rate of treatment with VENISTAR^Ⓡ was 97.7% (Tables 2 and 3). A total of 19, 6, 15, and 20 patients were followed-up for >300 days, 200~300 days, 100~200 days, and <100 days, respectively. Two patients with partial regurgitation were treated with ultrasound-guided sclerotherapy 239 and 344 days postoperatively. Complications included 20 cases of bruising, 3 cases of phlebitis, 2 cases of recanalization at the midthigh, and 1 case of neovascularization at the midthigh (Table 4). VCSS was 5 points preoperation, 2 points at 1 week postoperation, and 1.1 points at 1 month postoperation (Fig. 4).

Table 1 . Clinical characteristics of patients.

Variable	Male	Female
Sex (n)	41	19
Age (years)	46.2±11.7	52.7±14.2
Heights (cm)	174±5.9	160±6.7
Body weight (kg)	80.4±16.8	59.3±6.7
Body mass index	26.3±5.1	23.07±2.0
Treated veins (n=89)
Unilateral GSV	33 (57%)
Both GSV	23 (28%)
GSV+SSV	6 (9%)
Unilateral SSV	2 (3%)
Both SSV	2 (3%)

Table 2 . Follow up.

>300 days	19
200 days	6
100 days	15
<100 days	20
Mean F/U	190+130 days

Table 3 . Closure rate.

Treated vein (n)		Occluded vein (n)	%
GSV	79	77	97.4
SSV	10	10	100
Total	89	87	97.7

Table 4 . Postoperative complications.

Bruising	20
Phlebitis	3
Recanalization	2
Neovascularization	1
EHIT or DVT	0

Figure 4. VCSS (venous clinical severity score).

The cumulative closure rate was 90.7% (Fig. 5).

Figure 5. Cumulative closure rate.

The introduction of endovenous thermal ablation devices has changed the varicose vein treatment paradigm.

Radiofrequency and laser devices used for endovenous thermal ablation are recommended as the first-choice treatment for varicose veins in Europe and the United States. Compared to conventional surgical methods, such as high ligation and stripping, these devices show similar or improved treatment results and are associated with reduced levels of pain, faster recovery, and lower rates of complications (1,2).

In 1998, Closure^Ⓡ, the first-generation radiofrequency device was introduced (3). Subsequently in 2000, 810 nm LASER was developed (4), followed by ClosureFast^Ⓡ, the second-generation radiofrequency device in 2007 (5). However, first-generation radiofrequency thermal ablation devices have limitations, such as long operation time and risk of thrombosis. Therefore, laser ablation devices are preferred over radiofrequency thermal ablation devices in Korea. In 2007, the second-generation radiofrequency thermal ablation device, ClosureFast^Ⓡ (with the benefits of segmental ablation and high temperature that overcame the limitations of the first generation radiofrequency thermal ablation device) was introduced, competing with laser ablation devices.

ClosureFast^Ⓡ has a bipolar catheter and is coated with a positive temperature coefficient of resistance (PTCR) to maintain a constant temperature of 120℃ (6). This allows transmission of conductive heat with a constant temperature of 120℃ to the target vein wall. In contrast, VENISTAR^Ⓡ, the new radiofrequency thermal ablation device made in Korea, monitors the impedance rather than the temperature of the vein wall. An increase of 5 Ω from the baseline resistance stops the radiofrequency output. As the bipolar electrode is exposed, radiofrequency energy is directly transmitted to the vein wall and resistive heat is generated. To prevent overheating of the catheter owing to heat generated in the vein wall, VENISTAR^Ⓡ has a cooling system that circulates cold saline. Each cycle in ClosureFast^Ⓡ lasts for 20 s, and the number of cycles is determined by the operator. By contrast, the radiofrequency output of VENISTAR^Ⓡ is terminated automatically once the threshold resistance is reached. This minimizes the intervention of the operation for VENISTAR^Ⓡ, enabling more standardized procedures compared to ClosureFast^Ⓡ.

A catheter of ClosureFast^Ⓡ is coated to prevent carbonization. However, VENISTAR^Ⓡ has an exposed bipolar electrode, which leads to partial carbonization of the catheter. As a result, carbonization may induce errors in resistance measurements, which could subsequently cause insufficient ablation. Although this limitation is not a key issue in clinical practice, catheter carbonization in VENISTAR^Ⓡ remains a problem to overcome.

To treat large-diameter veins, the transfer of adequate energy with minimal damage to the surrounding tissues is essential, which often depends on the skill level and experience of the operator with existing thermal ablation devices (7). In contrast, VENISTAR^Ⓡ automatically stops the radiofrequency output when the threshold resistance is reached while monitoring the impedance of the vein wall, thereby improving the safety of the procedure. In our study, patients with relatively large veins were selected for treatment. Although larger diameter veins required a longer ablation time, numbness was not observed postoperatively, suggesting that VENISTAR^Ⓡ induced minimal thermal transfer to surrounding tissues. In a previous study, larger vein diameters were associated with a greater chance of recanalization, but radiofrequency ablation (RFA) was superior to stripping (8). Here, two cases of partial recanalization at the midthigh GSV were observed; however, these cases were easily treated with sclerotherapy under ultrasound guidance. The overall major complication rate based on pooled events in RFA cohort studies was 2.9% (9). Deep vein thrombosis (DVT) is a major adverse event. In a previous report, the incidences of DVT and EHIT were 0.7% and 0.4%, respectively (10). However, DVT and EHIT were not observed in this study.

The VENISTAR^Ⓡ radiofrequency thermal ablation device that directly delivers radiofrequency energy and monitors the impedance of the vein wall in the treatment of varicose veins was relatively safe and associated with a high success rate of treatment. However, as the follow-up period of the participants was relatively short, the generalization of the findings was limited. Thus, further long-term studies are warranted.

The authors have no conflicts of interest to disclose.