The Celon RFITT system comprises a bipolar CelonLab PRECISION power control unit with foot switch and a flexible bipolar Celon ProCurve 1200-S15 RFITT applicator (5F diameter catheter). The applicator, containing a thermal element is heated using the generator at a frequency of 470 kHz . The impedance of the venous tissue is continuously monitored and indicated by an acoustic signal (impedance feedback) on the power control unit allowing even and effective distribution of energy to the vein wall. The system allows the withdrawal speed of the catheter to be altered depending on the amount of energy required to maintain a consistent temperature of 85 °C.
RFiTT can be used under local and general anaesthesia, with and without an introducer sheath.
The technique of placement of the RFiTT applicator is very similar to that used for EVLA or the Closure Procedure. The treatment can be performed under general, regional or local anaesthesia according to local practice. Patients can have their GSV, SSV or anterior thigh Vein (ATV) cannulated by one of 2 methods. A 5F sheath (A similar diameter to the EVLA systems bit smaller than that used with the Closure system) can placed under duplex ultrasound guidance using the Seldinger method (ref). The applicator can then be passed through the sheath. It is also possible to pass the applicator catheter directly into the vein via a cut down without the use of a sheath (figure).
The Applicator tip is easily seen using Duplex ultrasound
The applicator catheter can be easily seen on duplex scanning where the anode and cathode produce visible acoustic shadows. This may be an advantage for clinicians new to the technique of endovenous ablation. As with other endovenous techniques, the applicator is passed up the vein to lie in a position 1-2 cm inferior to the saphenofemoral or sapheno-popliteal junction or just distal to the most proximal, competent tributary of the truncal vein..
Infiltration of Tumescent Fluid is not essential for treatments under General Anaesthesia.
It is not essential to use tumescent fluid to compress the vein when treatments are done under general anaesthesia. Unlike segmental RF ablation and EVLA where the catheter reaches temperatures of between 120C and 500C and tumescent infiltration is essential, patients can be treated without the additional cost or time involved in injecting fluid. This is because the RFiTT system uses a lower temperature than other devices so there is a reduced risk of thermal damage to surrounding tissues. In addition, the frequency of energy is higher than that to which local nerves are sensitive. This means there is a reduced risk of producing nerve injury by a Faradical effect
If a clinician chooses not to use tumescent fluid then it is important to elevate the patient’s leg during treatment. An alternative is to use, an esmarch bandage to compress the vein on to the applicator.
For those patients treated under local anaesthesia and for those where a clinician wishes to use tumescence under general anaesthesia, 0.9% NaCl Solution can be injected into the perivenous sheath under ultrasound control. For those under local anaesthesia, 50ml of 1% Xylocanie and 1ml 1:000 adrenaline should be added to 1 litre of saline. An alternative is to use chilled 0.9% NaCl (4C).
One the applicator is in position and the vein has been compressed by elevation, esmarch or tumescence, treatment can commence.
Heating can be stopped instantly using a footswitch control.
A foot switch is depressed to initiate the RF current and the applicator is withdrawn along the vein at a rate determined by a change in pitch of the acoustic signal. The pitch varies according to changes in temperature, power and impedance detected by the applicator tip and generator unit. One of the advantages of this method is that the current is switched off immediately the clinician removes their foot from the pedal. Thus like EVLA (when the laser is switched off immediately), the heating of the vein stops immediately. This is in comparison with segmental ablation when it can take some time for the catheter to cool. This might not seem too important, but when done under Local anaesthesia, an instant cessation in heating produces less pain for a patient, if the anaesthesia is inadequate, and reduces the risk of thermal damage to local structures. At this point more anaesthetic can be infiltrated or the catheter can be withdrawn slightly before treatment is re-started.
Feedback system prevents inadvertent skin burns
Thermal damage to the skin is avoided by the use of the RFiTT system as the energy automatically cuts out when the applicator feedback mechanism detects there is no connection with the vein. This does not occur with laser when an inattentive clinician may withdraw the fibre without stopping the laser. Skin damage using segmental ablation has been reported by several clinicians when they have withdrawn the applicator into the introducer sheath with part of the element within the patient and part in the sheath outside. As there is no feedback system with segmental ablation, there have been reports of full thickness burns to patients around the site of catheterisation.. Whilst this is an operator error, it is a complication that cannot occur with RFiTT because of the use of bipolar electrodes and the feedback system within the generator. As soon as the applicator enters the sheath, the current is switched off by a feedback mechanism.
The RFiTT applicator is not sensitive to thermal damage or fracture
There have been reports of laser fibres being damaged by needles used to infiltrate fluid during EVLA (ref). This damage can lead to abnormal heating and fibre fracture requiring open surgical retrieval of the broken parts. Similarly, there have been reports of the heating element of a segmental RF catheter melting because of inadequate or uneven compression. The RFiTT applicator has a bipolar system so only that portion of vein between the electrodes becomes heated. He applicator is robust enough to tolerate being touched by the infusion needle and this can be a helpful guide for the clinician to infiltrate fluid.
One RFiTT Applicator can be used for truncal and perforating veins
The same RFiTT catheter can be used for perforating veins if a clinician wishes to cannulated and treat an incompetent perforator at the same time as treating the GSV or SSV. This avoids the cost associated with the use of a segmental catheter for the truncal vein and an additional device for the perforator. EVLA is not used for perforating veins.
The RFiTT applicator has no guidewire channel.
The applicator lacks a guidewire channel so, unlike the EVLA systems and segmental RF system it can be difficult to negotiate a tortous section of truncal vein. This problem can be overcome by manual manipulation of the applicator under ultrasound control or the use of a longer 6F sheath. The latter can be placed using an .035 guidewire and standard catheter manipulation and exchange techniques. Ther is some advatantage to there being no guidewire channel. Air cannot be drawn into the patient through the channel and the is less blood loss if the cap to the channel on other systems is not secured.
Skills used with EVLA can be easily transferred to RFiTT.
Both EVLA and RFiTT require the clinician to slowly withdraw the catheter or applicator respectively. For RFiTT with the power unit set at between 10W and 18W, the pull back rate of 1cm every 2 to 3 seconds is similar to that required for EVLA. If a clinician wishes to use RF instead of EVLA (perhaps because of the disadvantages of Laser systems) then their skills learned are easily transferable.
The RFiTT system can be used on veins that are less than 7cm long
The RFiTT applicator tip has a ‘working’ section that is only 1.5cm long. This means that short sections of veins ( like the small saphenous vein) can be cannulated without the concerns attached to longer RF devices. If the vein is less than 7cm in length then a 7cm RF system would either be in the deep vein or would pass through the skin, resulting in damage.