Initial outcomes of endovenous laser ablation with 1940 nm diode laser in the treatment of incompetent saphenous veins

Abstract

Objectives

To investigate the initial outcomes of 1940 nm diode laser in the treatment of incompetent saphenous veins.

Methods

This was a prospective observational study. We treated 89 patients with 160 incompetent saphenous veins using a 1940 nm diode laser and bare fiber. The laser’s power was set to 4.5 W with a mean linear endovenous energy density of 50.4 J/cm.

Results

The one-month closure rate was 100%. The post-procedural pain score at 6 h, 1 day, 10 days, and 1 month was 0.85 ± 1.04, 0.65 ± 1.01, 0.82 ± 1.25, and 0.47 ± 0.82, respectively. Complications encountered included paresthesia (3.8%) and thrombophlebitis (4.4%), whereas no cases of endovenous heat-induced thrombosis were observed.

Conclusion

The 1940 nm laser and bare fiber at 50.4 J/cm showed satisfactory initial outcomes with less pain and fewer complications, in the treatment of incompetent saphenous veins.

Keywords

Varicose veins endovenous laser ablation endovenous laser treatment 1940 nm bare fiber

Introduction

The treatment of varicose veins has developed greatly over the past few decades. The transition from surgical stripping to endothermal ablation, which has become the primary treatment method for varicose veins, in the United States and United Kingdom, represents one of these developments.^1–3 Among the reasons for the widespread adoption of endothermal ablation are the faster recovery time and fewer complications than seen with surgical stripping. Wound complications and nerve injury occur in 3–10% and 2–39% of patients, respectively, after surgical stripping, while wound complications are rare and nerve injury occur in only 3% of the patients after thermal ablation.¹

Currently, the endothermal ablation method most commonly used worldwide is endovenous laser ablation (EVLA). EVLA uses thermal energy produced by laser to ablate the vein’s wall inducing the occlusion of the varicose vein. EVLA is less invasive and is associated with faster recovery compared to conventional surgical stripping.^1–3 There have been various advances in the laser wavelengths used for EVLA.^1,4–6 Previously used wavelengths were shorter, in the range of 810, 940, and 980 nm, and had high hemoglobin (Hb) absorption, while the currently utilized wavelengths are longer, in the range of 1064, 1320, 1470, 1500, and 1940 nm, and have higher water absorption.^4–6 Although there are several explanations about the mechanism of EVLA, these have not been clearly identified yet.^7–9 In addition, there is no unified treatment protocol outlining the optimal laser wavelength (nm), power (W), and pullback speed (mm/s).^4,5

Theoretically, the higher the water absorption of laser, the higher is the vein wall absorption of laser achieved.^4,5,9 After the introduction of 1470 nm laser that has a higher water absorption than Hb absorption rate, effective treatment with lower laser power (W) and linear endovenous energy density (LEED; J/cm) than earlier methods has become possible, reducing the complications associated with thermal damage. Using 1470 nm, satisfactory outcomes have been achieved mostly at LEED <100 J/cm.^10–13 However, there are few studies on the effective power or LEED at a longer wavelength of 1940 nm, and all have focused on radial fibers.^6,14–16 In addition, no studies have specifically investigated the Asian population.

This study aimed to investigate the initial outcomes and efficacy of using 1940 nm diode laser and bare fiber at 4.5 W and 50 J/cm for treating incompetent great (GSV) and small saphenous veins (SSV).

Methods

Patients

This was a prospective observational study. Between 24 June and 16 November 2017, 160 incompetent saphenous veins in 89 patients were treated at a single center by a single surgeon using 1940 nm diode laser at 4.5 W and bare fiber. The surgeon had experience with treating several hundred patients with EVLA using a 1470 nm diode laser as well as several thousand patients with various other procedures, including radiofrequency ablation (RFA), surgical stripping, and cyanoacrylate closure.

All targeted veins for treatment needed to demonstrate at least 0.5s of reflux in the standing position with a diameter of at least 3 mm. The preoperative clinical, etiologic, anatomic, pathophysiologic (CEAP) classification was defined as C1 (telangiectasia or reticular veins), C2 (varicose veins), C3 (edema), C4a (pigmentation or eczema), C4b (lipodermatosclerosis or atrophie blanche), or C5 (healed ulcer). We included eight patients with C1 disease who had symptoms such as aching, cramping, heaviness, tingling, and edema. Pregnant women and patients with occlusive arterial disease or deep vein insufficiency were excluded from the study, while no limitation was placed on the vein diameter. Written informed consent was obtained from all the patients.

For initial basic testing, the revised venous clinical severity scores (rVCSS) and Aberdeen varicose vein questionnaires (AVVQ) were used, while post-treatment pain was assessed using a numerical pain rating scale (NRS; 0–10).^17,18

This study was approved on 29 January 2018 by the Korea National Institution for Bioethics Policy (approval number: P01-201801–21-004) and conforms to the Declaration of Helsinki (1964; Hong Kong version, 1989).

All analyses were performed with SPSS version 18.0 (IBM, Armonk, NY).

Procedures

On the day of treatment, the location of the veins being treated was mapped on the patient’s leg with sonogram confirmation (P7; GE Healthcare, Chicago, IL) in the standing position. Local anesthesia was used in all patients along with light intravenous sedation using propofol (120 mg/12 mL) or midazolam (3 mg/3 mL) under the supervision of an anesthesiologist.

All GSV approaches were made from the mid-calf area below the knee joint, while SSV approaches were made from the lower calf area. A 16-gage angio needle was used for vein puncture and, without using any separate introducer sheath or guide wire, a bare fiber (Diotech, Korea) was inserted directly into the 16-gage needle for approach up to the deep vein junction. Tumescent solution was used by mixing 20 cc of 2% lidocaine with 500 cc Hartman solution, and perivenous infiltration was performed using a motor pump while under ultrasonographic guidance (LOGIQe, GE Healthcare). For supra-fascial GSVs, sufficient infiltration was achieved at least 10 mm from the skin. However, when such a 10 mm of distance could not be achieved, even with subdermal and intradermal infiltration, partial stripping or sclerotherapy were performed.

With the patient in the 30° Trendelenburg position, ablation was performed starting at 2 cm below the junction between the deep and saphenous veins without manual compression. Ablation was performed using a 1940 nm diode laser (Diotech, Korea) with power set at 4.5 W. The pullback speed was controlled according to the surgeon’s discretion based on changes in the diameter, while trying not to exceed a mean LEED of 50 J/cm whenever possible. For the area below the knee, ablation was performed at 3 W and 15 J/cm after sufficient tumescent infiltration while checking the adjacent relationship with the saphenous nerve. For cases with a rather close relationship, foam sclerotherapy with 1% sodium tetradecyl sulfate was performed to prevent thermal damage to the saphenous nerve.

Upon completion of the procedures mentioned above, concomitant phlebectomy or sclerotherapy was performed on branching varices or reticular vein/telangiectasia to produce a better cosmetic outcome during the one-stage procedure.

The patients were discharged 4–6 h after the procedure with instructions for appropriate ambulation. Nonsteroidal anti-inflammatory drugs were administered for five days post-procedurally, and the patients were recommended to wear a 20–30 mmHg compressive stocking for two weeks. No other thrombophylactic medication was administered.

The pain NRS was measured at 6 h, 1 day, 10 days, and 1 month after the procedure. On the 1st and 10th days, the patients were asked about their pain and adverse events by telephone interviews. A follow-up sonogram was performed at one month. A single patient with one incompetent saphenous vein was left out, and the follow-up rate was 99.4%

Results

The overall characteristics of the patients and treated veins are shown in Table 1. A total of 160 incompetent saphenous veins (112 GSVs and 48 SSVs) in 89 patients, were treated. The mean age of the patients was 47.1 ± 12.6 years and there were 68 females (76.4%). Sixty-five patients (73.0%) were classified as C2, while eight (9.0%), seven (7.9%), and one (1.1%) were classified as C3, C4, and C5, respectively. The number of patients who had one saphenous vein treated was 34 (38.2%), while 42 (47.2%), 8 (9.0%), and 5 (5.6%) patients had 2, 3, and four saphenous veins treated, respectively. Baseline rVCSS and AVVQ were 4.12 ± 1.52 (1–8) and 16.0628 ± 7.4900 (4.033–41.77), respectively.

Table 1.

Baseline patient characteristics.

Variables	Mean ± SD (Range) or No. (%)
No. of patients	89
Mean age (years)	47.1 ± 12.6 (21–74)
Female (n)	68 (76.4%)
Mean BMI (kg/m²)	22.5 ± 3.1 (16.1–32.4)
CEAP
C1	8
C2	65
C3	8
C4	7
C5	1
No. of treated saphenous veins per patient
1	34
2	42
3	8
4	5
No. of treated veins
GSV	112
SSV	48
Mean diameter (mm)
Total	6.7 ± 2.9 (3.0–17.8)
GSV	6.5 ± 3.1 (3.0–17.8)
SSV	7.4 ± 2.0 (3.7–13.1)
Mean length of treated veins (cm)
Total	33.1 ± 14.1 (8–76)
GSV	40.5 ± 9.8 (13–76)
SSV	15.8 ± 4.0 (8–25)
Mean LEED (J/cm)
Total	50.5 ± 12.3 (15.8–93.7)
GSV	46.3 ± 9.3 (15.8–75.1)
SSV	60.3 ± 13.1 (39.1–93.7)
No. of patients with concomitant procedures
Miniphlebectomy	45 (50.6%)
Sclerotherapy	40 (44.9%)

LEED: linear endovenous energy density (J/cm); GSV: great saphenous veins; SSV: small saphenous vein; BMI: body mass index; CEAP: clinical etiologic anatomic pathophysiologic; LEED: linear endovenous energy density.

The treated veins had a mean diameter of 6.7 ± 2.9 mm and a mean length of 33.1 ± 14.1 cm, while the mean LEED was 50.5 ± 12.3 J/cm. The number of patients who underwent concomitant phlebectomy and sclerotherapy was 45 (50.6%) and 40 (44.9%), respectively.

There were no severe adverse events, but pigmentation, paresthesia, and thrombophlebitis were found in one (0.6%), six (3.8%), and seven (4.4%) veins, respectively. All thrombophlebitis were mild and relieved with oral analgesics. Moreover, no infection or EHIT/DVT occurred. The post-procedural pain score with visual analogue scales at 6 h, 1 day, 10 days, and 1 month were 0.85 ± 1.04, 0.65 ± 1.01, 0.82 ± 1.25, and 0.47 ± 0.82 points, respectively.

Discussion

Although there are several theories about the exact mechanism of EVLA, they can largely be categorized into those based on an optical-thermal response, with laser energy being directly absorbed by the vein wall, and heat generation and transfer caused by carbonized blood.^5,19 The former posits that laser barely passes through the blood and reaches the vein wall to cause direct damage, whereas the latter proposes that the damage is mediated by blood, which can be explained by direct contact, heat conduction, steam bubble, and heat pipe principles.

Absorption of laser at specific chromophores varies according to the wavelength, and different materials are known to have different absorption coefficients.^5,6,19 During EVLA, laser is absorbed by Hb, water, and perivenous tissue. Previously used lower wavelengths (800–900 nm) showed higher absorption coefficients for Hb than water. Therefore, they were absorbed mostly by the blood, and the primary mechanism of EVLA was based on direct contact, heat conduction, steam bubbling, and the heat pipe principle from the carbonized blood and coagulum generated at the fiber tip. Accordingly, Proebstle et al.²⁰ reported that intravascular blood played a key mediating role in this heat damage process.

Subsequently, after the introduction of water-specific higher wavelengths, the chromophore changed from Hb to water in the vein wall, and the optical-thermal response became more significant. Theoretically, the absorption coefficient of the vein wall for a 1940 nm laser is more than four times higher than that for 1470 nm and more than 200 times higher than that for 980 nm (Table 2).^5,6,19 According to Vutlsteke et al.,⁵ circumferential laser absorption in the vein wall is important for effective treatment, and in an animal experiment on goat veins using 1500 nm and a tulip fiber, higher intraluminal blood volume resulted in less vein wall damage, which indicated that blood emptying is more important than had been previously thought.

Table 2.

Absorption coefficient of the blood and vein wall for the various laser wavelengths.

λ (nm)	μ_a (1/mm)
λ (nm)	Blood	Vein wall
810	0.21	0.2
840	0.21	0.18
940	0.28	0.12
980	0.21	0.1
1,064	0.12	0.12
1,320	0.3	0.3
1,470	3.0	2.4
1,950	10.0	7.5

λ: wavelength; μ_a: absorption coefficient.

Meanwhile, in an optical-thermal mathematical modeling study, Poluektova et al.²¹ reported that 45% of the laser was already absorbed by the thin layer of carbonized blood on the fiber tip, and the actual proportion being directly absorbed by the vein wall after bypassing the surrounding blood was very little at 1470 or 1940 nm. Consequently, the effects of the optical-thermal response generated from the laser being directly absorbed by the vein wall were not very significant.¹⁹

Such findings were somewhat contradictory to the results of Vutlsteke et al. The absorption coefficient of laser is higher in the blood than in the vein wall. In other words, even if the laser is at a water-specific wavelength, because the absorption coefficient is higher in the blood than in water, the claim that the main mechanism involves heat generated from the laser being absorbed by the surrounding blood, rather than being absorbed directly by the vein wall, is more convincing. However, in cases with almost no surrounding blood due to sufficient tumescent infiltration, the energy being directly absorbed by the vein wall would be relatively higher, and if the water absorption coefficient had increased, the resulting effect would have a larger impact, which is also convincing. Moreover, since the absorption coefficient of both blood and water would increase together with the increasing wavelength, it can be surmised that treatment would be possible with lower power regardless of the main absorption site. Additional human studies are needed on which mechanism are responsible for which outcomes.

So far, no common protocol for power or LEED when using EVLA with a 1470 nm laser has been developed. Doganci et al.¹⁰ reported that when 30 patients were treated using a 1470 nm laser and a radial fiber at 15 W and 90 J/cm, the six-month closure rate was 100%. That study also reported an equivalent six-month closure rate using a 980-nm laser and bare fiber with the same power and LEED settings.

In contrast to bare fibers, radial fibers can ablate the vein walls circumferentially with the laser light emitted radially penetrating into the vein wall. However, with bare fibers, direct contact between the unevenly placed heated tip and the vein wall results in heterogeneous ablation of the vein.⁹

In addition, other studies that used 1470 nm also reported high closure rates of 94.7–100% with LEED set to <100 J/cm, while a review also reported that effective treatment can be achieved with <85 J/cm (Table 3).⁴

Table 3.

Previous reports of EVLA with a 1470 nm laser.

	Wavelength (nm)	No. of subjects	Fiber type	Power (W)	LEED (J/cm)	Follow-up period (months)	Closure rate (%)
Doganci		30	Radial	15	90	6	100
Schwarz	1470	168	Bare	15	79.4	3	100
Schwarz	1470	144	Radial	10	57.4	3	100
von Hodenberg	1470	308	Radial	10	58.1	12	99.6
Sanioglu	1470	55	Radial	–	70	6	100
Mendes-Pinto	1470	42	Radial	10	24.7	12	94.7
Hirokawa	1470	215	Bare	6–12	85.1	24	100
Hirokawa	1470	177	Radial	10	81.4	48	100

EVLA: endovenous laser ablation; LEED: linear endovenous energy density.

On the other hand, reports investigating 1940 nm wavelengths are still very much lacking. Although there have been few studies, the results show that satisfactory outcomes can be achieved with LEED level below or above 50 J/cm, which represents levels lower than those needed when using 1470 nm (Table 4).

Table 4.

Previous reports of EVLA with a 1940 nm laser.

	Wavelength (nm)	No. of subjects	Fiber type	Power (W)	LEED (J/cm)	Follow-up period	Closure rate (%)
Schmedt	1940	177	Radial	–	GSV 59.2SSV 47.3	12 months	98.3
Viarengo	1940	41	Radial	4.06	45.3	467–1360 days	95.1
Mendes-Pinto	1940	48	Radial	5	17.8	12 months	87.5
Sroka	1940	72	Radial	–	64.3	6 months	100

EVLA: endovenous laser ablation; LEED: linear endovenous energy density.

As mentioned earlier, because 1940 nm has a higher water absorption coefficient than 1470 nm, theoretically, comparable treatment outcomes can be expected with lower power and LEED. However, more studies are needed and the complex mechanisms of EVLA mean its ultimate effects in humans cannot be easily predicted.

When lower power and LEED are used, the resulting thermal damage to the normal perivenous normal tissue also decreases, and early recovery may be expected with less post-procedural pain.

In this study, the patients’ pain scores were consistently below 1 point from the surgery and thereafter. Based on our previous experience of using a 1470 nm laser and bare fiber at 10 W and mean LEED of 84.8 J/cm to treat 158 patients, post-procedural pain scores of 1.35, 1.51, 1.81, and 0.89 points at 6 h, 1 day, 10 days, and 1 month, respectively, were achieved (unpublished data).

During EVLA treatment, perforation caused by direct contact is less common with radial fibers than bare fibers, and because circumferential thermal damage occurs more efficiently, effective treatment is possible with lower power and less post-procedural pain.^10,11,22 In the days of this study, there was no reliable radial fibers in Korea, while radial fiber was about 3–4 times more expensive than bare fiber. We are currently performing EVLA using ball-tip and radial fibers and we plan to report the findings shortly.

This study reported the satisfactory initial outcomes of treating incompetent saphenous veins using a 1940 nm laser and bare fiber at 4.5 W and a mean LEED of 50.5 J/cm, which is lower than settings used in the existing literature that tend to use wavelengths shorter than 1470 nm. Our review of the literature found only four studies using 1940 nm results, all of which were performed with a radial fiber; among them, two studies did not specify the power. To the best of our knowledge, our study is the first to report the results of 1940 nm EVLA with a bare fiber. Another advantage of our study is its prospective observational design and clear delineation of power and LEED.

Our study is not without its limitations. These include its short-term follow-up and single center setting. Larger studies with longer follow-up are needed to validate our findings.

Conclusions

The biological mechanism of EVLA in humans has not been clearly identified yet. Moreover, there are no common treatment protocols for different wavelengths and fiber types. We performed EVLA for incompetent saphenous veins using 1940 nm and a bare fiber at 4.5 W and a mean LEED of 50.5 J/cm, achieving satisfactory initial treatment outcomes with 100% closure rate and very low pain scores and a low complications rate. Additional studies with more long-term follow-up are needed.

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.

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