Tissue Ablation: Applications and Perspectives

Tissue ablation techniques have emerged as a critical component of modern medical practice and biomedical research, offering versatile solutions for treating various diseases and disorders. Percutaneous ablation is minimally invasive and offers numerous advantages over traditional surgery, such as shorter recovery times, reduced hospital stays, and decreased healthcare costs. Intra-procedural imaging during ablation also allows precise visualization of the treated tissue while minimizing injury to the surrounding normal tissues, reducing the risk of complications. Here, the mechanisms of tissue ablation and innovative energy delivery systems are explored, highlighting recent advancements that have reshaped the landscape of clinical practice. Current clinical challenges related to tissue ablation are also discussed, underlining unmet clinical needs for more advanced material-based approaches to improve the delivery of energy and pharmacology-based therapeutics.

Laser ablation on vascular diseases: mechanisms and influencing factors

Vascular diseases, such as venous insufficiency and coronary artery diseases, have been threatening the health of people. Efficient treatment with proper postoperative care is required to relieve the pain of the patients. Traditionally, venous insufficiency is treated with ligation and stripping, an open surgery whose complication rate cannot be ignored. Coronary artery disease is often treated with balloon angioplasty during which undilatable lesions may be encountered, limiting the efficacy of this approach. With advances in laser photonics and percutaneous coronary intervention procedure, laser ablation is emerging as an alternative and adjunctive therapy for these diseases. Endovenous laser ablation has the advantages of high success rate, low complication risk, and fast postoperative recovery. Laser ablation in arteries can handle uncrossable or undilatable lesions with a low incidence of serious complications. In this review, previously published research concerning vascular diseases and their therapies are analyzed in order to provide a clear explanation of the mechanisms and merits of laser ablation. For endovenous laser ablation, the main mechanisms are steam bubbles, heat conduction, and heat pipe, and three main influencing factors are wavelength, fiber types, and laser energy density. For excimer laser coronary atherectomy, the main mechanisms are photochemical, photothermal, and photomechanical effects, and three main influencing factors are catheter, medium, and laser parameters.

Approach to tortuous vena saphena magna with insufficiency: Foam scleroterapy

OBJECTIVE

This study aimed to investigate the efficacy of foam sclerotherapy in the treatment of tortuous Great Saphenous Vein (GSV) insufficiency.

METHODS

In this prospective non-randomized study 62 patients with tortuous GSV insufficiency were included. All patients were delivered sclerosant agent in the form of foam into the GSV through a cannula above the knee level. Characteristics of patients, diameter of veins, reflux grades, Venous Clinical Severity Score (VCSS) and Clinical, Etiological, Anatomical, Pathological (CEAP) scores, concentration of sclerosant agent, complications and follow-up results were recorded.

RESULTS

Foam sclerotheraphy was performed with 100% technical success in all patients at operative room. There were no allergic reactions or neurological complications during and after the operations. Ecchymosis was the most common complication with 37.1% frequency. . VCSS scores significantly decreased from 6.43% to 2.53%, during follow-up from initial admission to sixth months, respectively (P<0.05).In the first month parameters, successful occlusion rate was 88.7%, whereas its rate was 82.3% in sixth month. Recanalization rate significantly increased from 11.3% to 17.7% during follow-up from first to sixth months, respectively (P<0.05).

CONCLUSIONS

Due to its low complication rate, low cost, acceptable total occlusion rate and reproducibility; Foam sclerotherapy can be considered a reliable treatment for patients with tortuous GSV insufficiency.

The origin of loud claps during endovenous laser treatments

Optoacoustic and ultrasound methods have shown that the loud "claps" perceived by patients and medical staff during endovenous laser ablation (EVLA) are caused by volumetric blood boiling when large vapor-gas bubbles appear and collapse under the action of laser radiation, which is well absorbed in water. Acoustic effects when using lasers in the near infrared range (1.94, 1.47, and 0.97 μm) were studied in an experiment with non-deaerated water, as well as in EVLA. The nature of these acoustic signals was investigated using high-speed video recording. It turned out that the amplitude of the emerging acoustic pulses in the case of surface boiling, which prevails when using lasers with a wavelength of 0.97 μm, is two orders of magnitude smaller than in the case of volumetric boiling (1.94 and 1.47 μm). The reasons for the decrease in sound effects in this case are associated with numerous microbubbles at the tip of the laser fiber. The results obtained may be useful for further understanding of the mechanisms of EVLA.

Dual-modality fibre optic probe for simultaneous ablation and ultrasound imaging

All-optical ultrasound (OpUS) is an emerging high resolution imaging paradigm utilising optical fibres. This allows both therapeutic and imaging modalities to be integrated into devices with dimensions small enough for minimally invasive surgical applications. Here we report a dual-modality fibre optic probe that synchronously performs laser ablation and real-time all-optical ultrasound imaging for ablation monitoring. The device comprises three optical fibres: one each for transmission and reception of ultrasound, and one for the delivery of laser light for ablation. The total device diameter is < 1 mm. Ablation monitoring was carried out on porcine liver and heart tissue ex vivo with ablation depth tracked using all-optical M-mode ultrasound imaging and lesion boundary identification using a segmentation algorithm. Ablation depths up to 2.1 mm were visualised with a good correspondence between the ultrasound depth measurements and visual inspection of the lesions using stereomicroscopy. This work demonstrates the potential for OpUS probes to guide minimally invasive ablation procedures in real time.

Review on Laser Technology in Intravascular Imaging and Treatment

Blood vessels are one of the most essential organs, which nourish all tissues in our body. Once there are intravascular plaques or vascular occlusion, other organs and circulatory systems will not work properly. Therefore, it is necessary to detect abnormal blood vessels by intravascular imaging technologies for subsequent vascular treatment. The emergence of lasers and fiber optics promotes the development of intravascular imaging and treatment. Laser imaging techniques can obtain deep vascular images owing to light scattering and absorption properties. Moreover, photothermal and photomechanical effects of laser make it possible to treat vascular diseases accurately. In this review, we present the research progress and applications of laser techniques in intravascular imaging and treatment. Firstly, we introduce intravascular optical coherent tomography and intravascular photoacoustic imaging, which can obtain various information of plaques. Multimodal intravascular imaging techniques provide more information about intravascular plaques, which have an essential influence on intravascular imaging. Secondly, two laser techniques including laser angioplasty and endovenous laser ablation are discussed for the treatment of arterial and venous diseases, respectively. Finally, the outlook of laser techniques in blood vessels, as well as the integration of laser imaging and treatment are prospected in the section of discussions.

No significant difference between 1940 and 1470 nm in endovenous laser ablation using an in vitro porcine liver model

Current endovenous laser ablation (EVLA) practice favours 1470 nm, as water is a major chromophore for this wavelength. Water has a greater affinity for 1940 nm, leading to claims that lower powers or linear endovenous energy densities (LEEDs) are needed. We compared the thermal spread and carbonisation of EVLA using these two wavelengths, in the porcine liver model. Using the previously validated porcine liver model, we performed 5 treatments, at each power: 2 W, 4 W, 6 W, 8 W and 10 W using a standard pullback of 8 s/cm. This gave LEEDs for each wavelength of 16, 32, 48, 64 and 80 J/cm. Digital images were given random codes and analysed by two blinded observers. Thermal spread was measured using "SketchandCalc" online software and graded carbonisation from 0 (none) to 3 (black carbon tract). There was no significant difference in thermal spread between the two wavelengths at 6 W, 8 W and 10 W. At 2 W, the 1470-nm laser had a significantly increased thermal spread over the 1940 nm. Significantly more carbonisation was found with the 1940-nm laser compared to 1470 nm. In this model, there was no significant difference in thermal spread at powers of 6 W and more. At 2 W and potentially 4 W, 1470 nm showed spread than 1940 nm, due to increased absorption at the device/tissue interface. At powers and LEEDs used for saphenous ablation, we found no evidence to support reduced power or LEED when using 1940 nm. However, 1940 nm may be more advantageous than 1470 nm when ablating small thin-walled veins, near to the skin.

Morphological changes of veins and perivenous tissues during endovenous laser coagulation using 2-μm laser radiation and various types of optical fibers

OBJECTIVE

To determine the morphological changes in veins and perivenous tissues after endovenous laser coagulation (EVLC) using laser radiation with a wavelength of 1910 nm and different types of fibers (bare tip and radial).

METHODS

The EVLC procedure was carried out on 22 surface veins of six sheep. The radiation source was a diode-pumped solid-state laser, which was based on a LiYF₄:Tm crystal and had an emission wavelength of 1910 nm and a maximum output power of 10 W. Two types of optical fibers were used: (1) bare tip and (2) radial or radial with two rings. Histological and morphometric methods were used, and the statistical digital data were analyzed.

RESULTS

The use of a linear endovenous energy density of 20 J/cm and optical bare fibers for veins with diameters of 3-4 mm resulted in a slit-shaped or wide venous wall perforation. A thermal effect was observed on the perivenous connective tissue (PVCT), which caused damage to its structures. Wide perforations were accompanied by complete destruction of the PVCT in the projection of the formed defect. The distance between the remaining vein wall fragment, located opposite to the perforation, and injured small vessels was 257.7 ± 23.6 μm. The radius of thermal damage increased to 2073.5 ± 8.0 μm near the vessel perforation. Using optical radial fibers for veins with diameters of 3.9 ± 0.5 mm did not lead to perforations. The destructive effect of the laser on small vessels of the PVCT extended to a distance of 425.7 ± 22.0 μm.

CONCLUSIONS

Analysis of thermal vessel damage in perivenous tissue after EVLC with bare-tip fiber shows that in the projection of a wide perforation, the damaged vessels of the PVCT are located at a large distance from the coagulated vein wall. On the opposite side of the perforation, the distance from the coagulated vein wall to the damaged vessels of the PVCT is significantly reduced because of the minimal output of laser radiation energy through the poorly damaged part of the wall. Using an optical radial fiber facilitates the application of a uniform distribution of thermal energy to the vein wall and damage to all its layers; at the same time, it minimizes the thermal energy that extends beyond the vein wall and damages the surrounding tissue.

CLINICAL RELEVANCE

The use of radiation with a wavelength of 1910 nm will make it possible to carry out endovenous laser coagulation of varicose veins at lower power values compared with radiation in the micron and one and a half micron regions of the spectrum. Understanding of morphological changes of veins and perivenous tissues after endovenous laser coagulation with 1910-nm laser radiation and different types of optical fibers (bare-tip, radial, radial 2ring) help predict possible complications and reduce their rate.

Current strategies for endovascular management of varicose veins: An updated review of superficial ablation technologies

Chronic venous insufficiency (CVI) which causes varicose veins and venous ulcers, is a major cause of morbidity and mortality in the general population. The last several years have witnessed many revolutionary developments in the realms of minimally invasive techniques (both thermal and non-thermal) to treat CVI. Moreover, multiple newer societal recommendations have been published over the past one year on the basis of the current evidence. In this article, we will briefly summarise the imaging for varicose veins and review the existing evidence in literature as well as the current guidelines and recommendations for the management of varicose veins, especially focusing on the various superficial ablation technologies.

Scoping review of non-thermal technologies for endovenous ablation for treatment of venous insufficiency

INTRODUCTION

The aim of this review article is to compare the outcomes of newer non-thermal endovenous ablation techniques to thermal ablation techniques for the treatment of symptomatic venous insufficiency.

EVIDENCE ACQUISITION

Three independent reviewers screened PubMed® and EMBASE® databases to identify relevant studies. A total of 1173 articles were identified from database search that met our inclusion criteria. Two articles were identified through reference search. Removal of duplicates from our original search yielded 695 articles. We then screened these articles and assessed 173 full-text articles for eligibility. Subsequent to exclusion, 11 full-text articles were selected for final inclusion.

EVIDENCE SYNTHESIS

The non-thermal techniques are similar to thermal techniques in terms of a high technical success rate, closure rate at 12 months, change in Venous Clinical Severity Score and change in quality of life after procedure. However, the length of procedure is shorter for non-thermal modalities and patient comfort is improved with lower pain scores. Return to work may also be earlier after non-thermal ablation. The rates of bruising, phlebitis and paresthesia are higher after thermal ablation.

CONCLUSIONS

The non-thermal modalities are safe and effective in treating venous reflux and have shown improved patient comfort and shorter length of procedure which may make them favorable for use compared to the thermal modalities.

Endovenous laser ablation: A comprehensive review

OBJECTIVE

To provide an evidence-based overview of endovenous laser ablation and describe its role as an effective and durable technique for the management of superficial venous insufficiency.

METHODS

The published literature on the treatment of varicose veins using endovenous laser ablation was reviewed. The literature search focused on the history of endovenous laser ablation, its safety and durability, known complications, and differences in outcomes based on the iterations of fiber type and laser wavelength.

RESULTS

Treatment safety and efficacy of endovenous laser ablation appear to be based on the amount of energy administered over a defined distance, or the linear endovenous energy density. The ideal linear endovenous energy density varies with the laser wavelength and fiber-type. Post-operative pain and bruising may be reduced by the use of higher wavelength fibers or the use of radial or jacket-tip fibers as compared to bare-tip fibers. The incidence of endothermal heat-induced thrombosis remains low and has declined with increasing experience. Reports have demonstrated a greater than 90% technical success rate with saphenous endovenous laser ablation, long-term durability of ablation, and commensurate improvement in quality of life.

CONCLUSIONS

Endovenous laser ablation is a safe and durable treatment option for the management of incompetent superficial and perforator veins of the lower extremities. As an endothermal technology, it remains a key component of the standard of care for the treatment of chronic venous insufficiency.

Histopathologic differences in the endovenous laser ablation between jacketed and radial fibers, in an ex vivo dominant extrafascial tributary of the great saphenous vein in an in vitro model, using histology and immunohistochemistry

OBJECTIVE

The study aimed to investigate the biologic effects of the 1470-nm endovenous laser (EVL), with a jacketed fiber and a radial fiber, during EVL ablation of an ex vivo dominant extrafascial tributary of the great saphenous vein in our in vitro model by histology and immunohistochemistry.

METHODS

Ten segments of the dominant extrafascial tributary of the great saphenous vein were harvested by a consultant vascular surgeon from patients during routine varicose vein surgery. Six segments were treated using an ex vivo model of our design by a 1470-nm EVL with a jacketed fiber. The other four segments were also treated by a 1470-nm EVL but with a radial-firing fiber. Each segment was split into five sections and treated at five different linear endovenous energy densities (LEEDs) at 10 W: 0, 20, 40, 60, and 80 J/cm. The veins were incubated and subsections collected at 6 and 24 hours after treatment. Subsections were immersed in buffered formalin and taken for histologic and immunohistochemical analysis. Histopathologic analysis was then performed.

RESULTS

Treatment with the radial fiber led to a pattern of damage that was more homogeneous than with the jacketed fiber, with no carbonization of tissue present. Significant transmural damage and necrosis were observed at LEEDs of 60 and 80 J/cm in both treatment groups. At the same LEEDs, p53 and caspase 3 analysis showed that transmural cell wall vein death (necrosis or apoptosis) occurred by 6 hours after treatment with both fibers.

CONCLUSIONS

There was a significant difference in the effects of treatment with a jacketed fiber and a radial fiber in EVL ablation in vitro. Although both fibers caused transmural vein wall cell death at similar LEEDs, the pattern of damage with the radial fiber was more homogeneous. There was no overtreatment of tissue in terms of carbonization after treatment with the radial fiber. Treatment with the jacketed fiber showed carbonization of tissue at the same LEEDs.

Radiofrequency Ablation Increases the Incidence of Endothermal Heat-Induced Thrombosis

BACKGROUND

Endovenous thermal ablation has become the procedure of choice in the treatment of superficial venous reflux disease. The current armamentarium of devices and techniques aimed at the elimination of saphenous reflux offers surgeons and interventionalists a variety of treatment options; however, there is a lack of data comparing the safety of these products. The most concerning complication after endovenous thermal ablation is endothermal heat-induced thrombosis (EHIT) due to the risk of progression to deep venous thrombosis. This study aimed to compare the incidence rate of EHIT between radiofrequency ablation (RFA) and endovenous laser therapy (EVLT).

METHODS

This was a single-center, office-based, retrospective study over the course of 5 years, in which 3,218 consecutive patients underwent 10,029 endovenous saphenous ablations. The patient cohort was 66.2% female, with an average age of 61.9 years. At the time of each individual intervention, 24, 212, 3,620, 4,806, 200, and 1,167 patients had Clinical-Etiology-Anatomy-Pathophysiology disease 1, 2, 3, 4, 5, and 6, respectively.

RESULTS

There was a total of 3,983 EVLT and 6,091 RFA procedures. The most common vessel treated was the great saphenous vein, 63.6% of the time, followed by the small saphenous vein (25.6%), accessory saphenous vein (6.1%), and perforator vein (4.6%). There were 186 cases of EHIT, with 137 (73.6%) identified as type 1 as per the Kabnick classification. Endovenous ablation performed via RFA resulted in significantly more cases of EHIT than of EVLT (109 vs. 77; P = 0.034; odds ratio = 1.52), which was confirmed by a multivariate analysis.

CONCLUSIONS

In the largest single-center study of endovenous saphenous ablations to date, RFA was shown to pose a significantly higher risk of EHIT than of EVLT.

Three-year follow-up and quality of life of endovenous radiofrequency ablation of the great saphenous vein with the ClosureFast™ procedure: Influence of BMI and CEAP class

Purpose Endovascular ablation of the great saphenous vein has been proposed as a less invasive alternative to conventional ligation and stripping of varicose veins. Outcomes of patients treated with the radiofrequency ablation ClosureFast™ system over an eight-year period from a single-center were evaluated. Methods Three-year follow-up data included duplex ultrasound scan, complication rate, and questionnaires to assess patients' QOL, level of pain, and days off work. Results A total of 1080 consecutive patients (49.5 ± 18.6 years, 72% female, mean body mass index: 25.44 ± 4.1 kg m^-2) underwent radiofrequency ablation for incompetent saphenous veins in a single institution. Occlusion of the great saphenous vein was obtained in 98.6% and 93.8% cases at the end of the procedures and within 36 months, respectively. Only three deep venous thromboses and minor complications occurred in this series throughout the first week from the procedure. A decrease of the external vein diameter, equal to 72.7% and 31.1% of the pretreatment diameter, was observed at 1 week and 36 months, respectively. The average Aberdeen Varicose Vein Questionnaire score improved from 18.06 ± 9.47 before treatment to 11.56 ± 10.23 at 12 months, with no significant differences in the subsequent follow-up. SF-36 QOL scores significantly improved after the procedure in all domains, while there were no changes over time. Patients reported a prompt return to normal daily activities (1.5 ± 0.7 days) and work (3.1 ± 1.9 days). Body mass index influenced QOL scores, while it did not affect great saphenous vein diameter reduction during the follow-up. On the contrary, Clinical Etiologic Anatomic Pathophysiologic class significantly influenced both great saphenous vein diameter reduction after the treatment and QOL scores within 36 months. Conclusion Results of this retrospective monocentric, large patients study suggest that radiofrequency ablation of the great saphenous vein may be a safe and efficient alternative to conventional surgery.

Endovenous Laser Application

Introduction: Endoluminal vein treatment is a promising minimal invasive treatment option for peoples suffering from varicose veins. The basic mechanism underlying this procedure is to selectively induce heat in the vessel wall with the result of denaturation of proteins and shrinkage of collagen fibers due to energy application. So far energy could be applied either as RF-current, laser light or water steam. The different approaches to deliver such forms of energies are described.

Methods: Investigations on heat dependent vein tissue effects were performed. The degree of shrinkage and wall thickening due to heat induction was calculated. Tensile test on vein tissue were performed. Investigation using the radial emitting laser fibre in the ox-foot-model under reproducible condition were done and wavelengths dependent tissue reaction were explored.

Results: The experiments clearly demonstrate the degree of the shrinkage of length and diameter, the thickening of the vein wall, as well as the decrease of the elasticity of the tissue. The optical irradiation pattern of the radial emitting laser fiber serves for safe and reproducible energy application directly to the vein wall. Using a laser wavelength with high absorption by the tissue water needs reduced irradiation and irradiance compared to wavelengths with less water absorption. Conclusion: An experimental approach to improve laser application for endovenous varicose treatment is described. Laser parameters and treatment parameters were found which are now under clinical testing. The demonstrated tissue effects may help to find further arguments for clinical findings and sensations described by the patients during follow-up.

Influência da termoablação com baixa e alta densidade de energia na junção safeno-femoral, utilizando laser endovenoso 1470 nm

Contexto

Faz-se importante o conhecimento técnico dos ajustes de potência e de densidade de energia linear endovenosa (linear endovenous energy density, LEED) adequados para atingir o objetivo final da termoablação endovenosa (endovenous laser ablation, EVLA).

Objetivos

Avaliar a influência de diferentes LEEDs em termos de patência e presença de refluxo, bem como determinar a evolução clínica.

Métodos

Foram incluídas 60 veias safenas magnas (VSM). Os pacientes foram randomizados em dois grupos: EVLA com baixa potência (7 W e LEED de 20-40 J/cm) e com alta potência (15 W e LEED de 80-100 J/cm). O acompanhamento com eco-Doppler e escore de severidade clínica venoso (VCSS) foi realizado nos intervalos de 3-5 dias, 30 dias, 180 dias e 1 ano após o procedimento.

Resultados

Dezoito pacientes (29 membros) tratados com 7W de potência e 13 pacientes (23 membros) com 15 W completaram o estudo. Não houve diferença significativa considerando idade, tempo de cirurgia e o uso de analgésicos, lateralidade, gênero e presença de comorbidades. O LEED médio foi de 33,54 J/cm no grupo de 7 W e de 88,66 J/cm no de 15 W. Ambos apresentaram melhora no VCSS, redução significativa dos diâmetros da JSF e ausência de diferença significativa quanto ao aumento do comprimento do coto da VSM e de refluxo após o tratamento.

Conclusões

A utilização de maior densidade de energia mostrou-se mais efetiva em relação à estabilização do comprimento do coto da VSM e do refluxo em 6 meses. Fazem-se necessários estudos com um período de acompanhamento maior para fundamentar essa hipótese.

Endoluminal application of glass-capped diffuser for ex vivo endovenous photocoagulation

Endovenous laser ablation (EVLA) has frequently been used to treat varicose veins for 20 years. In spite of 90˜95% occlusion rates, clinical complications such as burn and ecchymosis still occur due to excessive thermal injury to perivenous tissue. In the current study, a glass-capped diffusing applicator is designed to validate the feasibility of EVLA as an effective therapeutic device by applying circumferential light distribution. The proposed device is evaluated with a flat fiber as a reference in terms of temperature elevation, fiber degradation, and degree of coagulative necrosis after 532 nm-assisted EVLA at 100 J/cm. The diffusing fiber generates a 40% lower maximum temperature with a 90% lower transient temperature change in blood, compared to the flat fiber. Due to low irradiance (13.5 kW/cm² ) and wide light distribution, the diffuser tip experiences no significant thermal degradation while severe carbonization occurs at the flat fiber tip. Ex vivo tissue tests verify that the diffusing fiber induces circumferential and consistent tissue denaturation to the vein wall (107.8 ± 7.8 µm) along with 19% vessel shrinkage. The proposed glass-capped diffusing applicator can be a feasible therapeutic device for EVLA with minimal complications by entailing low maximum temperatures and uniform tissue denaturation in the venous tissue.

The role of laser power and pullback velocity in the endovenous laser ablation efficacy: an experimental study

Endovenous laser ablation is an effective and minimally invasive alternative to surgical removal of incompetent veins. However, many controversies concerning optimal laser parameters usage in this procedure still remain. The purpose of this experimental study was to assess the adequate parameters required for vein wall destruction and to evaluate the role of fiber pullback velocity on vessel wall degradation. Varicose vein segments were treated with 1470-nm diode laser 3 to 9.5 W in power. The fiber moved through the vein at a velocity of 0.7 or 1.5 mm/s; the applied linear endovenous energy density (LEED) was 40-95 J/cm. The temperature of the vein surface in the course of laser irradiation was controlled by IR thermography. The intact collagen in treated vein specimens was studied by differential scanning calorimetry. The increase in the surface temperature with applied energy was found to be about three times slower for the pullback velocity of 0.7 mm/s than that of 1.5 mm/s. The collagen in the tissue was totally denatured in the case of the surface temperature of about 91 °C. The critical values of LEED ensured complete degradation of vein wall were of 53 and 71.5 J/cm for velocities of 1.5 and 0.7 mm/s, respectively. Our experimental study supports the conception that it is laser power and pullback velocity rather than LEED value that determine the temperature as well the collagen framework degradation and therefore the thermal response of procedure.

Association between antithrombotic therapy and risk of postoperative complications among patients undergoing endovenous laser ablation

BACKGROUND

The aim of the study was to evaluate the clinical results and postoperative complications, especially recanalization or bleeding complications, in patients with saphenous varicose veins undergoing endovenous laser ablation (EVLA) while receiving antithrombotic therapy (ATT).

METHODS

This retrospective cohort study included 1136 Japanese patients undergoing EVLA with a 980-nm diode laser between January 2012 and November 2015 at our institution. The patients were divided into two groups: ATT users (ATT group) and nonusers (control group). The ATT group was further divided into two subgroups according to whether the patients received antiplatelet or anticoagulant therapy. Clinical outcomes and postoperative complications among these patients were assessed.

RESULTS

Approximately 20% of the patients undergoing surgery for saphenous varicose veins at our institution received ATT. Of these, 141 (12.4%) received antiplatelet therapy and 95 (8.4%) received anticoagulant therapy. Successful occlusion of the full length of the treated vein was achieved in 99.9% of the patients; there were no severe perioperative complications. Endovenous heat-induced thrombosis occurred in 2.4% of patients, whereas postoperative complications developed in 1.2% of patients. One patient experienced recanalization (0.08%). There were no significant between-group differences in the incidence of recanalization and postoperative complications on univariate analysis.

CONCLUSIONS

The clinical outcomes and postoperative complications of EVLA in the ATT group were equivalent to those in the control group, indicating that EVLA can be safely performed in patients receiving ATT.

Investigation of endovenous laser ablation of varicose veins in vitro using 1.885-μm laser radiation

This paper presents the results of endovenous laser ablation (EVLA) of varicose veins in vitro using radiation of a solid-state laser based on the crystal LiYF4:Tm, with a wavelength of 1.885 μm and power output of around 3 W. An experimental series with saline solution and red blood cell (RBC) suspension in the venous lumen was performed to identify the impact of a heated carbonized layer precipitated on the fiber end face versus the efficiency of EVLA. Results of these experiments confirmed that the presence of a heated carbonized layer on the fiber end face increases the efficiency of EVLA.

The 1,470-nm bare-fiber diode laser ablation of the great saphenous vein and small saphenous vein at 1-year follow-up using 8-12 W and a mean linear endovenous energy density of 72 J/cm

PURPOSE

To demonstrate 1-year outcomes after low-energy endovenous laser ablation (EVLA) of incompetent saphenous veins with linear endovenous energy density (LEED) of 80 J/cm or lower with the use of a 1,470-nm diode laser.

MATERIALS AND METHODS

Incompetent saphenous veins in 236 patients (355 limbs; Clinical/Etiology/Anatomy/Pathophysiology classifications of C2-C4) were treated by EVLA with a bare-tipped 1,470-nm laser with LEED no greater than 80 J/cm (mean, 72.4 J/cm) and laser power of 8-12 W. Patients were evaluated clinically and with duplex ultrasonography at 1 week and 1, 3, 6, and 12 months after EVLA to assess the technical and clinical success and complication rates.

RESULTS

In the 355 limbs, the technical success rate was 100%. The great saphenous vein (GSV) remained occluded in all 229 limbs (100%) after 1 week, 202 of 203 limbs (99.5%) after 1 month, 157 of 158 limbs after 3 months (99.3%), all 99 limbs after 6 months (100%), and all 41 limbs after 1 year (100%). The small saphenous vein (SSV) remained occluded in all 103 limbs (100%) after 1 week, all 94 limbs (100%) after 1 month, 68 of 69 limbs (98.5%) after 3 months, 40 of 41 limbs (97.5%) after 6 months, and all 14 limbs after 1 year (100%). Two GSVs and two SSVs were recanalized and underwent repeated EVLA. No major complications occurred, although bruising (21% of cases), pain (15%), and paresthesia (4%) were observed.

CONCLUSIONS

Low-energy EVLA with the use of a 1,470-nm laser with LEED of 80 J/cm or lower is an effective, safe, and technically successful option for the treatment of incompetent saphenous veins.

Endovenous laser with miniphlebectomy for treatment of varicose veins and effect of different levels of laser energy on recanalization. A single center experience

Varicose veins, associated with great saphenous vein (GSV) incompetence, are traditionally treated with conventional surgery. In recent years, minimally invasive alternatives to surgical treatment such as the endovenous laser ablation (EVLA) and radiofrequency (RF) ablation have been developed with promising results. Residual varicose veins following EVLA, regress untouched, or phlebectomy or foam sclerotherapy can be concomitantly performed. The aim of the present study was to investigate the safety and efficacy of EVLA with different levels of laser energy in patients with varicose veins secondary to saphenous vein reflux. From February 2006 to August 2011, 740 EVLA, usually with concomitant miniphlebectomies, were performed in 552 patients. A total of 665 GSV, 53 small saphenous veins (SSV), and 22 both GSV and SSV were treated with EVLA under duplex USG. At 84 patients, bilateral intervention is made. In addition, miniphlebectomy was performed in 540 patients. A duplex ultrasound (US) is performed to patients preoccupying chronic venous insufficiency (with visible varicose veins, ankle edema, skin changes, or ulcer). Saphenous vein incompetence was diagnosed with saphenofemoral, saphenopopliteal, or truncal vein reflux in response to manual compression and release with patient standing. The procedures were performed under local anesthesia with light sedation or spinal anesthesia. Endovenous 980-nm diode laser source was used at a continuous mode. The mean energy applied per length of GSV during the treatment was 77.5 ± 17.0 J (range 60-100 J/cm). An US evaluation was performed at first week of the procedure. Follow-up evaluation and duplex US scanning were performed at 1 and 6 months, and at 1 and 2 years to assess treatment efficacy and adverse reactions. Average follow-up period was 32 ± 4 months (3-55 months). There were one patient with infection and two patients with thrombus extension into the femoral vein after EVLA. Overall occlusion rate was 95%. No post-procedural deep venous thrombosis or pulmonary embolism occurred. Laser energy, less than 80 J/cm, was significantly associated with increased recanalization of saphenous vein, among the other energy levels. EVLA seems a good alternative to surgery by the application of energy of not less than 80 J/cm. It is both safe and effective. It is a well-tolerated procedure with rare and relatively minor complications.

Randomized clinical trial of endovenous laser ablation versus steam ablation (LAST trial) for great saphenous varicose veins

BACKGROUND

The aim was to compare endovenous laser ablation (EVLA) and endovenous steam ablation (EVSA) for great saphenous varicose veins in a non-inferiority study.

METHODS

Patients with primary great saphenous vein reflux were randomized to EVLA (940 nm) or EVSA (SVS™). Primary outcomes were treatment success (vein obliteration or abolition of reflux) [corrected] at 52 weeks, and Venous Clinical Severity Score (VCSS) at 12 weeks. Secondary outcomes were pain, satisfaction with treatment, duration of analgesia use and days lost from daily activities, changes in Aberdeen Varicose Vein Questionnaire (AVVQ) and EQ-5D™ scores after 12 weeks, and complications at 2 and 12 weeks.

RESULTS

A total of 227 legs were treated (EVSA, 117; EVLA, 110); 36 legs treated with EVSA received a low dose and the remaining 81 a higher dose. At 1 year, the treatment success rate after high-dose EVSA was not inferior to that of EVLA: 92 (95 per cent confidence interval (c.i.) 86 to 98) versus 96 (92 to 100) per cent respectively. Changes in VCSS after 12 weeks were similar: -2·69 (95 per cent c.i. -2·34 to -3·04) and -2·51 (-2·10 to -2·93). AVVQ, EQ-5D™ and EQ VAS scores improved equally 12 weeks after both treatments. Patients treated with EVSA reported less postprocedural pain, fewer days of analgesia use, were more satisfied with therapy, and had a shorter convalescence. Complication rates were comparable.

CONCLUSION

The 1-year treatment success of high-dose EVSA was not inferior to that of EVLA. Several secondary outcomes were in favour of EVSA. Registration number NCT02046967 (http://www.clinicaltrials.gov).

Histological difference between pulsed wave laser and continuous wave laser in endovenous laser ablation

BACKGROUND

Endovenous laser ablation to saphenous veins has been popular as a minimally invasive treatment for chronic venous insufficiency. However, adverse effects after endovenous laser ablation using continuous wave laser still remain. Pulsed wave with enough short pulse duration and sufficiently long thermal relaxation time may avoid the excess energy delivery, which leads to the perforation of the vein wall.

METHOD

(1) Free radiation: Laser is radiated in blood for 10 s. (2) Endovenous laser ablation: Veins were filled with blood and placed in saline. Endovenous laser ablations were performed.

RESULTS

(1) There were clots on the fiber tips with continuous wave laser while no clots with pulsed wave laser. (2) In 980-nm continuous wave, four of 15 specimens had ulcers and 11 of 15 had perforation. In 1470-nm continuous wave with 120 J/cm of linear endovenous energy density, two of three presented ulcers and one of three showed perforation. In 1470-nm continuous wave with 60 J/cm of linear endovenous energy density, two of four had ulcers and two of four had perforation. In 1320-nm pulsed wave, there were neither ulcers nor perforation in the specimens.

CONCLUSIONS

While endovenous laser ablation using continuous wave results in perforation in many cases, pulsed wave does not lead to perforation.

Is the temperature of tumescent anesthesia applied in the endovenous laser ablation important? Comparison of different temperatures for tumescent anesthesia applied during endovenous ablation of incompetent great saphenous vein with a 1470 nm diode laser

Introduction

We aimed to investigate whether the temperature of tumescent anesthesia is important, if so, to establish an opinion about the ideal temperature.

Materials and methods

Endovenous laser ablations were performed in 72 patients; 35 patients (Group A) received tumescent anesthesia at +4℃, while other 37 patients (Group B) received tumescent anesthesia at room temperature. The groups were compared in terms of intraoperative pain, postoperative regional pain, ecchymosis, paresthesia, skin burns and necrosis. At month 1, great saphenous vein was evaluated for recanalization and patient satisfaction.

Results

The survey on intraoperative pain showed that patients receiving tumescent anesthesia at +4℃ experienced much less pain. Interestingly, statistical analysis showed that this difference was not significant ( p = 0.072). No skin burns or necrosis occurred in either group, whereas ecchymosis and paresthesia were the most frequently observed side effects in both groups, but no significant difference was found between the groups. There was no significant difference between pain levels on postoperative days and no significant difference between the groups in terms of satisfaction with endovenous laser ablation procedure and postoperative satisfaction. All venous segments treated with endovenous laser ablation in both groups were occluded. At month 1 no recanalization was observed.

Conclusion

We conclude that the temperature of tumescent anesthesia solution is not important, while the proper administration of tumescent solution in adequate amounts ensuring delivery of the fluid to all segments appears to be a more significant determinant for the success of the procedure.

Endovenous laser ablation (EVLA): a review of mechanisms, modeling outcomes, and issues for debate

Endovenous laser ablation (EVLA) is a commonly used and very effective minimally invasive therapy to manage leg varicosities. Yet, and despite a clinical history of 16 years, no international consensus on a best treatment protocol has been reached so far. Evidence presented in this paper supports the opinion that insufficient knowledge of the underlying physics amongst frequent users could explain this shortcoming. In this review, we will examine the possible modes of action of EVLA, hoping that better understanding of EVLA-related physics stimulates critical appraisal of claims made concerning the efficacy of EVLA devices, and may advance identifying a best possible treatment protocol. Finally, physical arguments are presented to debate on long-standing, but often unfounded, clinical opinions and habits. This includes issues such as (1) the importance of laser power versus the lack of clinical relevance of laser energy (Joule) as used in Joule per centimeter vein length, i.e., in linear endovenous energy density (LEED), and Joule per square centimeter vein wall area, (2) the predicted effectiveness of a higher power and faster pullback velocity, (3) the irrelevance of whether laser light is absorbed by hemoglobin or water, and (4) the effectiveness of reducing the vein diameter during EVLA therapy.

Temperature profiles of 980- and 1,470-nm endovenous laser ablation, endovenous radiofrequency ablation and endovenous steam ablation

Endovenous thermal ablation (EVTA) techniques are very effective for the treatment of varicose veins, but their exact working mechanism is still not well documented. The lack of knowledge of mechanistic properties has led to a variety of EVTA protocols and a commercially driven dissemination of new or modified techniques without robust scientific evidence. The aim of this study is to compare temperature profiles of 980-and 1,470-nm endovenous laser ablation (EVLA), segmental radiofrequency ablation (RFA), and endovenous steam ablation (EVSA). In an experimental setting, temperature measurements were performed using thermocouples; raw potato was used to mimic a vein wall. Two laser wavelengths (980 and 1,470 nm) were used with tulip-tip fibers and 1,470 nm also with a radial-emitting fiber. Different powers and pullback speeds were used to achieve fluences of 30, 60, and 90 J/cm. For segmental RFA, 1 cycle of 20 s was analyzed. EVSA was performed with two and three pulses of steam per centimeter. Maximum temperature increase, time span of relevant temperature increase, and area under the curve of the time of relevant temperature increase were measured. In all EVLA settings, temperatures increased and decreased rapidly. High fluence is associated with significantly higher temperatures and increased time span of temperature rise. Temperature profiles of 980- and 1,470-nm EVLA with tulip-tip fibers did not differ significantly. Radial EVLA showed significantly higher maximum temperatures than tulip-tip EVLA. EVSA resulted in mild peak temperatures for longer durations than EVLA. Maximum temperatures with three pulses per centimeter were significantly higher than with two pulses. RFA temperature rises were relatively mild, resulting in a plateau-shaped temperature profile, similar to EVSA. Temperature increase during EVLA is fast with a high-peak temperature for a short time, where EVSA and RFA have longer plateau phases and lower maximum temperatures.

Optical-thermal mathematical model for endovenous laser ablation of varicose veins

Endovenous laser ablation (EVLA) is successfully used to treat varicose veins. However, the exact working mechanism is still not fully identified and the clinical procedure is not yet standardized. Mathematical modeling of EVLA could strongly improve our understanding of the influence of the various EVLA processes. The aim of this study is to combine Mordon's optical-thermal model with the presence of a strongly absorbing carbonized blood layer on the fiber tip. The model anatomy includes a cylindrically symmetric blood vessel surrounded by an infinite homogenous perivenous tissue. The optical fiber is located in the center of the vessel and is withdrawn with a pullback velocity. The fiber tip includes a small layer of strongly absorbing material, representing the layer of carbonized blood, which absorbs 45% of the emitted laser power. Heat transfer due to boiling bubbles is taken into account by increasing the heat conduction coefficient by a factor of 200 for temperatures above 95 °C. The temperature distribution in the blood, vessel wall, and surrounding medium is calculated from a numerical solution of the bioheat equation. The simulations were performed in MATLAB™ and validated with the aid of an analytical solution. The simulations showed, first, that laser wavelength did virtually not influence the simulated temperature profiles in blood and vessel wall, and, second, that temperatures of the carbonized blood layer varied slightly, from 952 to 1,104 °C. Our improved mathematical optical-thermal EVLA model confirmed previous predictions and experimental outcomes that laser wavelength is not an important EVLA parameter and that the fiber tip reaches exceedingly high temperatures.

Minimally invasive treatment of varicose veins: Endovenous laser ablation (EVLA)

Varicose veins are a frequently encountered medical condition. In the era of minimally invasive surgery, several techniques, in the treatment of varicose veins, have been developed in the last few years. One of the most frequently used new techniques is endovenous laser ablation. Fibrotic sealing of the treated vein lumen is the final result. The vein ablation is obtained under local - tumescent anaesthesia and the patients can be treated in an office setting with immediate return to full activity. Safety and effectiveness seem to be the major characteristics and advantages of this technique.