Theory

How does Radiofrequency Ablation (RFA) work?

In simple terms, radiofrequency ablation (RFA) of varicose veins works by heating the varicose veins from the inside, causing the tissue to shrivel away and the vein wall to die. This closes the vein and stops the blood falling the wrong way, curing the varicose veins. By heating the vein, the vein wall is eaten away by the body and does not come back again. This is different from the old stripping technique where the vein was removed surgically, which has now been shown to cause the body to grow a new one back again. Although this sounds good, when a new vein grows it never has valves and so the new vein is automatically a new varicose vein rather than a new healthy vein.
 
Radiofrequency ablation (RFA) of varicose veins is one of the new "thermoablation" treatments of veins. ‘Thermoablation’ merely means:
 
‘Thermo’ - using heat
‘Ablation’ - means the destruction of tissue but in this sense, killing the tissue without removing it.
 
The other main thermoablation technique for veins is endovenous laser ablation (EVLA).
 
In order to get the heat to the vein wall, a radiofrequency ablation (RFA) device has to be inserted inside the vein ("endovenously"). This is achieved by using a very long thin tube or "catheter" that can be inserted into the vein under ultrasound control through a simple pinhole or tiny incision, usually no more than 2 mm long. Because of this, radiofrequency ablation (RFA) of varicose veins and endovenous laser ablation (EVLA) of varicose veins are often called "catheter based thermoablation techniques".
 
RFiTT-1 Positioning of the RFiTT (TM) catheter at the top of the great saphenous vein
  • The ultrasound guides the insertion and placement of the RFiTT catheter and guides the treatment

  • RFiTT catheter - two electrodes at the end close the vein with radiofrequency heating

  • The RFiTT catheter is pulled down the vein through the cannula at a set rate ensuring closure of the vein

 
The radiofrequency ablation (RFA) catheter or device is therefore a long thin tube with a handle or control device at the external end which connects by wire to the radiofrequency current generator, and at the tip which is internal to the patient, are the radiofrequency electrodes.
 
The initial devices for radiofrequency ablation (RFA) of varicose veins use the principle of bipolar radiofrequency ablation. In this situation, there were two electrodes. One at the very tip of the catheter and the second is placed a couple of millimetres back along the shaft. The gap of a couple of millimetres is very important.
 
When the catheter is placed inside the vein under ultrasound control, and is in the correct position, the vein has to be "squashed" or contracted tightly onto the catheter, ensuring a very good contact between the electrodes and the vein wall. When the radiofrequency current was then turned on, and electric current was passed first from the tip electrode, through the vein wall to the electrode which is placed 2mm down the shaft. This is then alternated and the current switched direction, flowing from the electrode further down the shaft through the vein wall and back into the electrode at the tip.
 
This swapping of current direction, or "alternating current" happened thousands or millions of times per second (thousands of times per second = kilohertz or KHz; millions of times per second = megahertz or MHz). Thus the alternating current is at radiofrequency rates.
 
The effect of the electrical current flowing first one-way through the vein wall, and then the other way before swapping back again at such high frequencies is the generation of heat. It is the flow of electrons vibrating as they flow through the vein wall in alternating directions that cause the heat to be generated in the tissue and cells of the vein wall. The tip of the bipolar radiofrequency ablation (RFA) device did not actually get hot at all itself, and heat was only generated if the electrodes were in good contact with biological tissue.
 
When the energy is controlled to heat the vein to exactly the right level, the vein wall is ablated (i.e. the cells in the vein wall are all killed by heat) and the vein closes stopping blood from flowing through it. As the cells are all dead, the body's immune system slowly reabsorbs the whole of the vein making the vein disappear and stopping it from regrowing again.
 
The first device to use this technology was the VNUS Closure device. However, the original VNUS Closure device had very small electrodes and the time taken to treat a vein was very long. VNUS decided to develop their system down a different route - however a newer system, the RFiTT device used this same principle but with far larger electrodes. This resulted in the RFiTT producing far more energy and is therefore able to treat veins much quicker.
 
RFiTT-2 Closing the Great Saphenous Vein with RFiTT radiofrequency ablation
  • The RFiTT device closes and destroys the vein by heat. The vein heals by 'fibrosis', preventing regrowth by neovascularisation

  • RFiTT catheter - radiofrequency current passes between the two electrodes at the end of the catheter, heating the vein

  • The RFiTT catheter is pulled down the vein through the cannula at a set rate ensuring closure of the vein

 
Although the bipolar radiofrequency ablation (RFA) techniques have been very successful for treating veins using the endovenous route, VNUS changed their device in the mid 2000's, with an aim to speed up treatment. This device is called the VNUS ClosureFAST device.
 
Similar to the bipolar radiofrequency ablation (RFA) devices, the VNUS Closure FAST is a long catheter that can be inserted endovenously under ultrasound control through a pinhole or tiny incision, usually less than 2 mm. The external end has a handle that is used to control the device and an electrical lead connecting it to the VNUS Closure FAST radiofrequency current generator. 
 
VNUS-1 Positioning the VNUS ClosureFAST catheter in the Great Saphenous Vein
  • Ultrasound probe used to guide the whole operation with the greatest accuracy

  • The VNUS ClosureFAST(TM) catheter is passed up the vein

  • The cannula is positioned into the vein under ultrasound control

 
However, unlike the bipolar radiofrequency ablation (RFA) devices, the tip actually gets hot itself, heating the vein by simple conduction. Of course as the tip is hot, it will heat anything it touches including blood, subcutaneous fat or skin if it is in the wrong position. In addition, this treatment is approximately 7 cm long, enabling long sections of vein to be treated at one time. This has advantages and disadvantages which will be discussed later. VNUS has just produced a 3cm version that has got over many of the disadvantages of having just a 7cm version (VENEFIT).
 
However as far as this discussion is concerned, the fact that the tip gets hot itself rather than radiofrequency current is causing heat to be generated in the vein tissue itself, causes some experts to suggest that the VNUS Closure FAST device is not actually true radiofrequency ablation (RFA) of varicose veins. It is a thermoablation of varicose veins - the radiofrequency current only being the source of heating the tip rather than the vein. 
 
VNUS-2 Closing the great saphenous vein with vnus closure fast tm
  • The ultrasound guides the closure of the vein

  • Vein closed in 6.5-7cm segments under tumescence (local anaesthetic) - from 2012 the vein can be closed in 3cm segments if needed

  • The VNUS ClosureFAST(TM) catheter is pulled back in segments

 
Therefore at the time of writing this, the only RFA catheter using bipolar radiofrequency is the RFiTT device. The VNUS ClosureFAST catheter is a widely used thermoablation catheter heated by radiofrequency current rather than true radiofrequency ablation.
 
Initial studies with the RFiTT catheter showed relatively good results, but there were some teething problems. However, following some prize winning research performed at The Whiteley Clinic (in the UK), the new Whiteley Clinic protocol for RFiTT has shown to be reliable in closing the Great Saphenous Vein (GSV) successfully in every treated vein, and also further studies from the same clinic have shown RFiTT can also be used to close incompetent perforating veins using the TRLOP technique.

As the VNUS Closure FAST is unable to close perforators (a different device is needed called the VNUS RFS device) this makes RFiTT more versatile.

Next Page: For which veins is Radiofrequency Ablation suitable for?

This website was last updated on 03/10/17.

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