Published online on 3 August 2012 Phlebology, doi: 10.1258/phleb.2012.012013
Original article
Radiofrequency-induced thermal therapy: results of a
European multicentre study of resistive ablation of
incompetent truncal varicose veins
B Braithwaite*, L Hnatek†, U Zierau‡, M Camci§, GJM Akkersdijk**, D Nio**,
M Sarlija††, M Ajduk††, P Santoro‡‡ and E Roche§§
*Queens Medical Centre – Vascular Surgery, Nottingham, UK; †Atlas Hospital, Zlin, Czech Republic; ‡Saphenion
Clinic, Berlin; §Mediapark Clinic, Cologne, Germany; **Spaarne Hospital, Hoofddorp, The Netherlands;
††
University Hospital Dubrava, Zagreb, Croatia; ‡‡Angiomedica, Roma, Italy; §§Platon Clinic, Barcelona, Spain
Abstract
Objectives: To investigate the effectiveness of bipolar radiofrequency-induced thermal
therapy (RFITT) in a multicentre non-randomized study.
Methods: Some 672 incompetent saphenous veins (85% great saphenous varicose vein, 15%
short saphenous vein) in 462 patients (56.5% CEAP [clinical, aetiological, anatomical and
pathological elements] class 3 or worse) were treated in eight European centres. Patients
were assessed between 180 and 360 days postoperatively. Occlusion rates were determined
by duplex ultrasound and compared with the power used for treatment, pull back rate
and experience of the operating surgeon.
Results: Complete occlusion rates of 98.4% were achieved when treatments were performed
by an experienced operator (more than 20 cases), when the maximum power setting on the
RFITT generator was between 18 and 20 W and the applicator was withdrawn at a rate slower
than 1.5 second/cm
Conclusions: RFITT is efficacious, well tolerated by patients and has a low incidence of
procedure-related post-operative complications.
Keywords: endovenous technique; endovascular treatment; varicose veins
Introduction
Treatment of great saphenous varicose veins (GSV)
has traditionally involved surgery, with an incision
at the groin and stripping of the GSV. This method
can cause significant postoperative pain and bruising and delayed return to normal activity.1,2
Complications include infection, haematoma and
saphenous nerve injury.3 – 5
Less invasive endovenous techniques have been
shown to be as effective as surgery in the treatment of varicose veins. They also produce less postCorrespondence: B Braithwaite, MChir MB FRCS,
Queens Medical Centre – Vascular Surgery, NG7 2UH,
Nottingham, UK.
Email: [email protected]
Accepted 22 April 2012
operative pain and bruising and enable early return
to normal activity.2,6 – 9 Some endovenous techniques use thermal energy to cause vein ablation:
endovenous laser ablation (EVLA), radiofrequency
ablation (RFA) and steam treatment. All three techniques use a catheter to deliver thermal energy to
the vein wall to cause venous occlusion. Early
reports suggest that there appear to be differences
in effectiveness and postoperative pain and bruising with RFA having slightly lower occlusion rates
but causing less pain and bruising than EVLA.6 – 8
There is currently little data on steam ablation.
While there are several manufacturers and wavelengths for EVLA there has only been one system
for RFA. The early catheter systems used resistive
heating of the vein wall to cause ablation (Closure
Plus, VNUS Medical Technologies, San Jose, CA,
USA). These systems were reported to produce
longer treatment times when compared with
DOI: 10.1258/phleb.2012.012013. Phlebology 2012:1–9
Copyright 2012 by the Royal Society of Medicine Press
Original article
B Braithwaite et al. Radiofrequency-induced thermal therapy (RFITT)
EVLA. More recently segmental ablation catheters
have been used which use conductive heating of
the vein using radiofrequency energy to heat a
7-cm coil (VNUS Closure Fast, VNUS Medical Technologies). For segmental ablation, as with EVLA,
tumescence anaesthesia or fluid is required to
reduce pain and thermal damage to surrounding
tissues and to compress the vein wall onto the catheter.
A minimally invasive bipolar radiofrequencyinduced thermotherapy (RFITT) technique (OlympusSurgical Technologies Europe/Celon AG, Teltow,
Germany) is widely used for minimally invasive
surgery for tumour ablation and palatal ablation.9 – 14
This RFA system has the capacity to treat truncal
varicose veins with and without tumescence.15
The aim of the study was to investigate the
effectiveness of RFITT for endoluminal treatment
of varicose veins.
Methods
Eight institutions in Germany, The Netherlands,
UK, Italy, Croatia, Czech Republic and Spain took
part. The recruitment of patients occurred during
a 45-month period between March 2005 and
December 2008.
Patients aged 18 years and above with varicosities of the GSV or short saphenous veins (SSV)
were eligible for inclusion. All patients had symptomatic varicose veins with a CEAP (clinical, aetiological, anatomical and pathological elements) class
1 – 6.16 Patients with deep vein thrombosis, fresh
thrombus in the vein to be treated, symptomatic
peripheral arterial disease, severe systemic diseases, extremely convoluted saphenous veins (that
might prevent insertion of the applicator) as well
as lactating mothers or pregnant women were
excluded. Patients had a preoperative duplex scan
confirming incompetence of the GSV or SSV and
venous morphology suitable for RFA. The venous
morphology was similar to that required for
EVLA or segmental RF Ablation. Veins up to
12 mm in diameter on duplex examination were
included.
The RFITT system was used for all treatments and
comprised the bipolar CelonLab Precision radiofrequency power control unit with foot switch and a
flexible bipolar RFITT applicator Celon ProCurve
1200 (Olympus Surgical Technologies Europe/
Celon AG, Teltow, Germany). The bipolar arrangement of electrodes of the applicator enabled a resistive heating of the vein wall to cause ablation and
closure of vein. The impedance of the venous
2
Phlebology 2012:1–9
tissue was continuously monitored and indicated
by an acoustic signal (impedance feedback) on the
power control unit allowing even distribution of
energy to the vein wall. This system also allowed
the withdrawal speed of the catheter to be altered
by the operator depending on the amount of
energy required. The applicator catheter was echogenic and easily seen on duplex scanning where
the two electrodes produced visible acoustic
shadows.
After a period of training in the technique and
approval from the relevant ethics or clinical governance committees, each investigator was asked to
evaluate the RFITT system. There was a variation
in the methods for inserting the RFITT catheter
and in the use of adjunctive procedures to treat varicosities. Prior to the training for this study, three
investigators had experience of endovenous
thermal ablation techniques while the remainder
had not used either EVLA or RFA prior to their
training for this study.
Procedures were performed under general,
regional or local anaesthesia according to local practice. Target veins were cannulated by one of two
methods: either a 5 F or 6 F sheath was placed at
the distal point of incompetence of the vein under
duplex ultrasound guidance using the Seldinger
method and the flexible RFITT applicator was then
passed through the sheath. Alternatively, the applicator catheter was passed directly into the vein via a
cut down without the use of a sheath. Once the
applicator was in the vein, it was passed proximally
to lie in a position 1 – 2 cm inferior to the saphenofemoral or saphenopopliteal junction. The applicator
had a rounded tip to minimize the risk of perforating the venous wall on correct use.
In some patients fluid (tumescence) was injected
into the perivenous sheath in a similar fashion to
that used for EVLA or segmental RFA. In some
cases, no fluid was injected and the leg was elevated
and treatment commenced. In others, there were
no injections but an Esmarch bandage was used
to compress the vein on to the applicator prior to
treatment. http://www.complete-feet.co.uk/minorsurgery/sterile-esmarch-bandage
The power output of the applicator was activated
by a foot switch via the power control unit. The
maximum output power was selected by the investigator at their discretion and preference: Settings
between 18 and 25 W were used during the course
of the study. Activation of the foot switch triggered
the release of radiofrequency energy as the applicator was slowly pulled back under control of the
audible impedance feedback. If coagulum collected
on the applicator tip, the applicator was removed,
B Braithwaite et al. Radiofrequency induced thermal-therapy (RFITT)
cleaned and re-inserted and the treatment recommenced.
Adjunctive procedures such as phlebectomies or
sclerotherapy were performed as necessary. Postoperative care was carried out according to local
policy but typically utilized a 15-cm crepe
bandage worn for one day followed by a light compression stocking worn for two weeks. Patients
were discharged the same day on recovery from
anaesthesia and successful ambulation. Analgesia
in the form of non-steroidal anti-inflammatory
medication was prescribed as necessary.
Follow-up investigations
Patients were asked to complete visual analogue
scores (VAS) for their perception of pain on days
1, 7 and 21. Clinical and postoperative duplex
follow-up was done after six and 12 months.
Duplex ultrasonography of the treated veins was
carried out to determine treatment success as
defined by:
† Complete ablation (closed) was defined as no flow
†
†
seen throughout the entire treated length of
vein;
Partial ablation (partial) was defined as no flow
seen in part of the treated length of vein but
some areas were still compressible and had
flow. In this category, the preoperative truncal
reflux had been abolished but the whole
length of the intended treatment zone had not
occluded;
Failed ablation (open) was any vein that had
truncal flow throughout the intended treatment
zone. This included patients where the vein
had narrowed and where the reflux was of a
shorter duration than had been detected on
the preoperative duplex scan.
The incidence of haematoma, pigmentation and
other skin changes as reported by the patient or
clinician were recorded. Patients were asked to
provide subjective assessment of their symptoms
and any complications were recorded (e.g. sensory
disturbances). Patients were asked to state their satisfaction with the procedure.
Data collection and analysis
Each investigator provided data using a standardized sheet which was sent to a central data collection centre. In addition to patient reported
outcomes, data included gender, age, treated
Original article
saphenous vein, CEAP classification (C1– 6),
method of anaesthesia, use of tumescence, selected
maximum output power, length of treated vein
segment, total time of energy application, and
occlusion status documented by duplex scan.
Data management and statistical analysis were
performed by professionals independent of the
investigators and the manufacturer of the RFITT
system.
Data were analysed for patients who had a final
follow-up between 180 and 360 days after treatment. The treatment time per centimetre and
power used were calculated for each treatment.
The outcome of treatment was compared with
three factors in order to identify the conditions for
the use of RFITT that resulted in the best occlusion
rates: (1) pullback rate, (2) power setting and (3)
experience of the operator.
Complications which were not related to the
RFITT procedure were not analysed (e.g. sideeffects of adjunctive procedures like phlebectomy
or sclerotherapy).
The Fisher’s exact test was used for statistical
analysis of contingency tables instead of chi-squared
test because the expected values in some of the
cells of the analysed contingency tables were
below 5. Because of multiple testing the Bonferroni
criterion was used to adjust the level of significance:
P ¼ 0.05/4 ¼ 0.0125.17 The statistical test was performed by using SPSS 17.0 (SPSS Inc., Chicago, IL,
USA).
Results
During the study period, 953 patients had 1400
incompetent truncal veins treated with RFITT
(1172 GSV and 228 SSV). Of the 953 patients, 462
patients completed follow-up between 180 and
360 days. The remainder did not attend for
medium term follow-up. The outcome data for the
462 patients who attended follow-up (569 GSV
and 103 SSV) were analysed.
The majority of patients had symptoms classified
as CEAP class 3 or worse (56.5%). Some 81.5% of
patients had general anaesthesia. Seventy-three
percent of patients had tumescence fluid injected.
The use of additional tumescence decreased
during the course of the study: while for the first
half of treatments in the study additional tumescence was used in 85.4%, only 60.7% of treatments
in the second half were combined with tumescence.
The average generator output power was set to
23 + 3 W. The mean length of vein treated was
50 + 20 cm and the mean total treatment time was
Phlebology 2012:1–9
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Original article
B Braithwaite et al. Radiofrequency-induced thermal therapy (RFITT)
Table 1 Patient data for all patients group and for the optimum group
Group
Patients ‡
Total
Man
Woman
Age § (years)
Total
Man
Woman
No. of veins treated
Vein Treated ‡
GSV
SSV
CEAP status ‡
CEAP 1
CEAP 2
CEAP 3
CEAP 4
CEAP 5
CEAP 6
N/A
Anaesthesia ‡
General
Spinal
Regional
Tumescence used‡
Maximum power output§ (W)
Length of vein treated§ (cm)
Treatment time §
(second)
(second/cm)
Follow-up period§ (days)
Occlusion status at last FU ‡
Closed
Partial
Open
All patients
Optimum group†
462
155
307
(100.0%)
(33.5%)
(66.5%)
120
37
83
(100.0%)
(30.8%)
(69.2%)
51 + 13
51 + 13
51 + 13
672
(21–90)
(23–90)
(21–87)
(1.5/pt.)
54 + 14
56 + 12
53 + 15
183
(21–90)
(39–90)
(21–86)
(1.5/pt.)
569
103
(84.7%)
(15.3%)
147
36
(80.3%)
(19.7%)
3
259
263
85
12
20
30
(0.4%)
(38.5%)
(39.1%)
(12.6%)
(1.8%)
(3.0%)
(4.5%)
0
42
83
46
0
2
10
(0.0%)
(23.0%)
(45.4%)
(25.1%)
(0.0%)
(1.1%)
(5.5%)
375
34
51
491
23 + 3
50 + 20
(81.5%)
(7.4%)
(11.1%)
(73.1%)
(18–25)
(5– 130)
115
2
3
45
19 + 1
48 + 17
(95.8%)
(1.7%)
(2.5%)
(24.6%)
(18–20)
(15–95)
89 + 66
1.8 + 1.3
290 + 84
(6– 478)
(0.3–8.3)
(180–360)
152 + 83
3.2 + 1.4
218 + 64
(26–478)
(1.5–8.3)
(180– 360)
621
30
21
92.4%
4.5%
3.1%
180
2
1
98,4%
1.1%
0.5%
pt., patient; FU, follow-up
All-patient group ¼ patients with last follow-up between 180 and 360 days after treatment
†
Optimum group ¼ treatments selected by (1) pullback speed 1.5 cm/second or slower, (2) maximum power 20 W or lower, (3) experience of
.20 treatments
‡
Number ( percentage)
§
Mean + standard deviation (minimum–maximum)
Number (mean number per pt.)
89 + 66 s which equates to a mean pullback rate of
1.8 + 1.3 s/cm.
After a mean follow-up period of 290 + 84 days,
621 veins (92.4%) were occluded, 30 (4.5%) were
partially occluded and treatment failed in 21
(3.1%). The results for all patients are summarized
in the left data column of Table 1 (all patients) and
in the Kaplan –Meier graph (Figure 1).
Complications
Complications occurred in 61 of 672 treatments
(9.1%). The numbers and the rates of complications
after procedure are shown in Table 2. The most
4
Phlebology 2012:1–9
frequent complication was sensory disturbance
which occurred in 5.8% of patients but this resolved
after a median of nine weeks. Other complications
included bruising, erythema, haematoma, hyperpigmentation, matting and phlebitis occurred with
frequencies below 1% each. There were no DVTs
and no thermal injuries.
Pain scores and patient satisfaction
The median VAS level for pain was 2/10 at one day
of follow-up which decreased to 1 after seven days
follow-up and was 0 at all subsequent follow-up
visits of 21, 180 and 360 days. Some 99.3% of
B Braithwaite et al. Radiofrequency induced thermal-therapy (RFITT)
Original article
Influence of the learning curve
Figure 1 Kaplan–Meier graph showing numbers at risk,
cumulative complete occlusion and combined complete and partial
occlusion rates over time for the whole cohort of veins treated with
RFITT (n ¼ 672). Complete or partial occlusion rates were 99.2% and
95.4% at 180 and 360 days (solid line). Complete Occlusion rates
were 98.5% and 88.2% (dash line) at 180 and 360 days
Operator experience influenced outcome. On
average, for the first 20 veins treated, only 76.3%
were completely occluded which was significantly
lower (P , 0.0001) compared with 96.5% when
more than 20 treatments had been performed by
the operator (Figure 3c).
A subgroup analysis was done to identify those
treatments where the operator was experienced
(more than 20 cases), the power setting was 18 –
20 W, and the pull back time was slower than
1.5 s/cm. There were 183 treatments in this category
(optimum group) and 98.4% of veins were completely occluded compared with 90.2% occlusion in the
other 489 treatments when power and pull-back
speeds were higher and experience less. This difference in outcome was both clinically and statistically
significant (P ¼ 0.001). This result is shown in
Figure 3d.
Discussion
patients were satisfied with the therapeutic/cosmetic outcome of treatment. Likewise 99.6%
would recommend the treatment method to others.
The effect of pullback rate
Figure 2 shows the effect of different pullback rate
in cm/s on occlusion rates. Occlusion rates were significantly higher (P ¼ 0.005) when pull back rates
were slower than 1.5 s/cm when compared with
faster pullback (Figure 3a).
Power setting
Power settings of between 18 and 20 W produced
complete occlusion in 95.3% of treatments compared with 91% when settings of greater than
20 W were used (Figure 3b). This difference was
not statistically significant (P ¼ 0.015).
Table 2 Complications after the RFITT procedure
Complications
No.
Rate [%]
Ecchymosis
Erythema
Hematoma
Hyper-pigmentation
Matting
Phlebitis
Sensory disturbance
6
2
2
6
2
4
39
0.9
0.3
0.3
0.9
0.3
0.6
5.8
Complication rate based on a total number of 672 treated veins
This study shows that RFITT is an effective method
for treating truncal varicose veins under local or
general anaesthetic. A 98.4% complete occlusion
rate can be obtained when the operator has experience of at least 20 treatments, uses a power setting
of between 18 and 20 W and pulls the applicator
back at a speed of 1.5 s/cm or slower.
This was a large international study in countries
with differing health-care systems. The design
included clinicians from different clinical centres,
ranging from ambulatory offices through day
surgery centres to hospitals. The multiple sources
of data should minimize the impact of differences
in clinical routine by individual surgeons, because
of different experience and personal preferences.
The results are therefore what other practitioners
might expect if they chose to use the RFITT system.
It was not possible to follow up all patients
because some were reluctant to return for appointments when they saw no need to do so. Nearly all
patients were happy with the outcome of their
vein surgery and would recommend it. It is
accepted by the authors that some patients may
not have returned for follow-up because their treatment had failed or they were unhappy with the
outcome. This is unlikely as the presented results
are comparable with the outcomes of other forms
of endovenous thermal ablation.
It is important to understand what the difference
is between RFITT, EVLA or VNUS ClosureFast in
the way energy is delivered to the vein.
Phlebology 2012:1–9
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B Braithwaite et al. Radiofrequency-induced thermal therapy (RFITT)
Figure 2 Pull back time and occlusion rates
The thermal effect of RFITT results in a shrinkage
and irreversible denaturation of collagen and other
cellular proteins. The structure of collagen changes
as its bonds break and it forms a gel-like substance
that acts as glue between vessel walls. To achieve
this effect the tissue needs to be heated to between
70 and 95 8C, sufficient for collagen and elastin in
the tissue to convert into gelatin.18 The thermal
energy with RFITT is not, as is the case with the
laser or VNUS ClosureFast, emitted by the catheter,
but originates directly in the venous wall. This was
how the original Closure plus system worked,
albeit with longer pull-back times than with the
RFITT system19 The RFITT applicator itself is not
actively heated and remains colder than the treated
tissue. There is therefore a lower risk of inadvertent
thermal injury. There were no thermal complications
in this study. The bipolar arrangement of the electrodes of the RFITT applicator creates an effect comparable to an ‘induction cooker’, with the venous wall
used as a conductor between the two poles. Radiofrequency energy can generate heat in biological
tissues by causing high frequency oscillations of
ions or water molecules.12 In an ex vivo study with
bovine veins heated in a water quench, it was
shown that the greatest shrinking by 36% as well
as the largest increase of wall thickness by 38%
was found at temperatures of 85 and 90 8C.
Histological analyses of treated veins from rabbit
ears and human veins obtained by stripping indicate that proteins of the venous endothelium are
converted into gelatin and then cause occlusion of
the venous walls.18
The energy applied to the tissue is an adequate
parameter to estimate the treatment effect, as the
heat dissipation and therefore the temperature
increase in the treated tissue region is proportional
to the energy applied. An often used ratio is the
so-called linear energy density, which is the
applied energy (in Joule) per length of the treated
vein (in centimetres). In laser treatments, a linear
6
Phlebology 2012:1–9
energy density of 60– 90 J/cm, depending on the
laser wavelength, is usually considered to result in
sufficient occlusion rates while keeping complications at an acceptable level.20
It is not appropriate to compare the energy used
for RFITT and the energy used for EVLA. The
ratio of linear energy density (J/cm), often quoted
with EVLA, does not consider all physical aspects
and is therefore only of limited suitability to
predict treatment success. Energy dissipation is a
three-dimensional effect, as heat is generated in
the tissue volume surrounding the energy source,
i.e. the tip of the catheter. The energy required to
sufficiently heat a vein segment of a certain length
depends, besides its length, on the diameter of the
vein segment and the thickness of the vein wall.
As a consequence, thicker vein segments require
more energy than thinner ones to achieve a sufficient thermal effect. In the case of the RFITT
system, the impedance control determines both
the emitted power and the withdrawal speed of
the catheter. The impedance, in turn, depends
on the dehydration of the tissue surrounding the
tip, which is related to the tissue temperature.
Therefore, more energy is applied to segments in
which more energy is required for a sufficient
heating effect (e.g. bigger vein wall thickness),
and less energy e.g. in thinner vein sections,
leading to an appropriate J/cm3 value while the
J/cm values will vary. As the vein diameters have
not been recorded in this study, further research is
required to evaluate this relationship.
Significantly better occlusion rates were achieved
when a lower power setting (20 W) and a slower
pull back rate was used 1.5 s/cm. This observation
suggests that a lower power setting leads to a
slower increase of tissue temperature; therefore, to
a slower dehydration and a slower increase of impedance. As a consequence, the withdrawal speed
needs to be lower. This again leads to a higher
energy emission to the vein wall resulting in a
B Braithwaite et al. Radiofrequency induced thermal-therapy (RFITT)
Original article
Figure 3 Rates of complete, partial and failed treatment by. (a) Pull back time in cm/s. (b) Treatment power. (c) Operator
experience. (d) Optimum group (all class criteria of right bars from a–c applied) versus other patients (none, only one, or only
two class criteria of right bars from a –c applied). Fisher’s exact test was used for P values.
more thorough vein wall protein denaturation. It is
possible that power settings of less than 18 W could
result in even better occlusion rates but those settings were not the subject of this study. Laboratory
studies would be required to confirm these hypotheses.
The use of tumescence is not mandatory when
using RFITT. Additional tumescence was used in
73% of all patients. Unlike ablation techniques
using conductive heating or laser, involving
temperatures of between 120 and 500 8C which
make tumescent infiltration essential, the results
suggest that patients can be treated with RFITT
without the additional cost or time involved in
injecting fluid. This is because the RFITT system
induces a lower temperature in the vein compared
with other technologies leading to a reduced risk
of thermal damage to surrounding tissue.
Patients had very little pain after the RFITT procedure with a maximum score on day 1 of 2 (VAS
Phlebology 2012:1–9
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B Braithwaite et al. Radiofrequency-induced thermal therapy (RFITT)
range 0 to 10). Kabnick reported an average pain
score of 2.2– 2.6 on a visual analogue scale of 0 – 5
after endovenous laser therapy.21 The reduced
pain with RFITT compared with 810-nm laser
EVLA has been re-ported previously in a study of
38 patients with bilateral disease.15 One of the
reasons for lower pain scores with RFITT may be
the significantly lower temperature used, combined
with the rounded catheter tip which reduces the
risk of mechanical injury of the vein wall.
Complication rates were similar to other methods
of endovenous thermal abalation. Haematoma
occurred in only two patients (0.3%), significantly
lower than reports on EVLA. Paresthesia, dysesthesia and hypoaesthesia were documented separately
but combined in the evaluation as sensory disturbances (5.8%), since in some patients both paresthesia and hypoesthesia was diagnosed. Sensory
disturbances could be caused by mechanical
injury during the intervention (including phlebectomies), through thermal destruction, or because
of postoperative inflammation during the reparative and reactive changes in the area surrounding
the vein. The latter might explain why symptoms
settled after a median of nine weeks.
One criticism of the study is that the diameter of
the treated veins was not recorded. There was no
record of selection or exclusion of patients on the
basis of vein diameter. The overall results do
reflect the performance of RFITT in a large and
diverse patient group that probably represents
that of daily practice in clinical reality. According
to the investigators, the largest vein diameters that
have been successfully treated in this study were
23 mm.
Long-term results of RFITT are not yet available.
Several studies have shown good results for RFA
up to 24 months and it is probable that the results
of RFITT will be similar.1,2,22,23 As most of these
technologies are new, the lack of long-term results
with a follow-up time of five years or more is a
general weakness for all endoluminal techniques.
Conclusion
This large multicentre study of RFA using the
RFITT method has demonstrated that it is efficacious, well tolerated by patients and has a low
incidence of procedure-related postoperative complications. Complete occlusion rates of 98.4% can
be achieved with adequate experience and the
correct settings.
Conflict of interest: All of the participants were
paid a small fee towards the cost of additional
8
Phlebology 2012:1–9
duplex scans for those patients recruited and
those who returned for follow-up. BB has been
paid expenses for advising Olympus Surgical Technologies Europe/Celon AG.
Funding: Olympus Surgical Technologies Europe/
Celon AG supplied the disposable applicators at
no charge.
Acknowledgement
The authors would like to thank Christine
Schweimler (Dipl. Biol.) for independent data management and analysis, and Dr Ulrich Gauger (Dipl.
Math.; www.statistikhilfe.de) for expert advice on
statistical analysis.
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