Endovenous Laser Therapy (ELT) Of Saphenous Vein Reflux Using Thulium Laser (Tm, 1940 nm) with Radial Fiber – One Year Results

Prospects of Endovenous Laser Ablation (EVLA) Standardization-Mid-Term Results of a Four-Zone Dosimetry Guiding Tool for 1940 nm Laser

BACKGROUND

Heterogeneity regarding dosimetry and reporting of endovenous laser ablation (EVLA) mandates the development of a standardized protocol. This study presents the mid-term results of EVLA with 1940 nm-laser and radial-fibre, supported by a four-zone dosimetry tool.

MATERIALS AND METHODS

Four anatomical dosimetry zones for great saphenous veins (GSV) and two for small saphenous veins (SSV) were defined with set power levels. Zone-1G (4 W) extended from the inguinal ligament to the apex of femoral triangle, Zone-2G (4 W) from the apex of femoral triangle to the upper border of patella. Zone-3G (3 W) from the patella to the tibial tuberosity. Zone-4G (2 W) extended from the tibial tuberosity to the ankle. Zone-1S from the sapheno-popliteal junction to the tibial tuberosity. Zone-2S from the tibial tuberosity to the ankle. Power was increased by 1 W for veins >10 mm and decreased by 1 W when fibre sticking was encountered. Pullback-velocity was max. 1 mm/s.

RESULTS

A total of 152 consecutive patients (185 procedures) were recruited. Mean follow-up time was 11.9 months. Mean linear endovenous energy density for GSV was Zone-1G:42 J/cm, Zone-2G:33 J/cm, Zone-3G:27 J/cm, Zone-4G:22 J/cm, Zone-1S:34 J/cm, Zone-2S:27 J/cm. Occlusion rates were 98.9% (1-month) and 93.7% (12-months). Complications at 1 M were low, namely laser-induced paraesthesia (LIP) 2.2% and endovenous heat-induced thrombosis (EHIT) 1.6%. Persistent LIP (12 M) was observed in 0.5%.

CONCLUSION

The proposed four-zone guiding tool is a step towards standardizing dosimetry and documentation for EVLA with 1940 nm. This strategy shows good mid-term results with minimal complications. Long-term follow-up and application in further centres are necessary to prove its reproducibility. Such a guiding tool could improve the ability to analyse, compare and review different EVLA wavelengths and fibre types.

Endovenous laser coagulation: asymmetrical heat transfer and coagulation (modeling in blood plasma)

The objective of this study was to describe the dynamics of blood plasma heating and coagulation processes carried out by continuous laser radiation with wavelengths 1.55 and 1.94 μm through bare-tip fibers and fibers with radial output (radial fibers) used for endovenous laser coagulation (EVLC). The study was performed in previously thawed frozen donor blood plasma using high-speed shooting of the heating process through the shadow optical method. It has been shown that in the case of highly water-absorbed laser radiations, convection, explosive, and small-bubble boiling play a major role in the process of heat transfer and coagulation. It has been shown that in the case of radiation with wavelength λ = 1.94 μm, effective heat transfer begins at significantly lower levels of power compared to radiations with λ = 1.55 μm. It has been established that heat transfer is sharply asymmetrical and is directed mainly upwards and forwards (bare-tip fiber) or upwards (radial fibers). For a wavelength of 1.94 μm, the effect of self-cleaning of the fiber surface from coagulated plasma fragments was found. Except for short-term acts of explosive boiling, the heat transfer is asymmetrical and directed mainly upwards. This effect should lead to uneven heating and thermal damage to the vein wall with the maximum at its upper part. For EVLC, the use of radiation with a wavelength of 1.94 μm is more efficient and safer.

Comparison of Short-Term Outcomes Between Endovenous 1,940-nm Laser Ablation and Radiofrequency Ablation for Incompetent Saphenous Veins

Background: Radiofrequency ablation (RFA) has shown faster recovery and lower pain scores compared to Endovenous laser ablation (EVLA) for treatment of varicose veins. However, a comparison of 1,940-nm EVLA and RFA has not been reported. This study compared short-term outcomes using 1,940-nm EVLA and RFA for varicose veins. Methods: Between April 2018 and June 2018, 43 patients (83 incompetent saphenous veins) were treated with 1,940-nm EVLA and 37 patients (64 incompetent saphenous veins) with RFA. Follow-up duplex was checked at 1 month and 3 months. Results: Baseline characteristics showed no significant differences between both groups except for age. Pain scores at 6 h, and at 1, 10, and 30 days after treatment showed no differences. Complications and time to return to normal activity showed no differences. The 100% closure rate was checked in both groups at 1 month and 3 months follow-up. Conclusion: Short-term outcomes showed no significant differences between 1,940-nm EVLA and RFA treatment.

Endovenous laser coagulation: asymmetrical heat transfer (modeling in water)

The objective of this study was to describe the dynamics of water heating carried out by continuous laser radiation with wavelengths 1.47, 1.55, and 1.94 μm with different types of fibers used for endovenous laser coagulation. The study was conducted in water using high-speed surveying of the heating process through the shadow optical method. It has been shown that in the case of highly water-absorbed laser radiations, convection and boiling play a major role in the process of heat transfer. It has been shown that in the case of radiation with λ = 1.94 μm that is heavily absorbed by water, effective heat transfer begins at significantly lower levels of power compared to the weaker-absorbed radiations with λ = 1.47 and 1.55 μm. Mathematical models based only on thermal conductivity inadequately describe the process of real heat transfer during endovenous laser coagulation. It has been established that heat transfer is sharply asymmetrical and is directed mainly up-and-forward (bare-tip fiber) or upward ("radial" and "two-ring" fibers). Heat transfer for laser light with wavelength 1.94 μm is most effective than for 1.47 and 1.55 μm.

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

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.