History of thermal ablation

Thermal ablation is a newer technique that uses a laser or high-frequency radio waves to create intense local heat in an incompetent vein. Heat is directed through a catheter to close up the targeted vessel. This treatment closes off the problem veins but leaves them in place so there is minimal bleeding and bruising.

VNUS Closure™ I – radiofrequency closure

There are several different techniques that can be used for venous ablation treatment. The first technique is a variation of a procedure that was first used in the 1930’s for the treatment of hemorrhoids, and is known as radiofrequency closure or VNUS Closure™. There are two quite different techniques that both use the title radiofrequency closure. With the first technique, which was developed in about 2000, a set of wires was inserted into the offending vein, and an electrical current was used to slowly heat the vein. The term radiofrequency is used because the frequency of the current that is used is just below the frequency of an AM radio station. This basic technique was essentially the same as bipolar electrocautery, which has been used routinely for decades for traditional surgical procedures. What set this treatment apart from bipolar electrocautery is that a very low current was used, resulting in treatment requiring minutes instead of seconds to achieve the desired effect. Typically, the treatment took about 30 minutes per vein, and the set of wires was slowly withdrawn during this time to ensure treatment of the entire course of the vein.

VNUS Closure™ II – ClosureFast radiofrequency ablation

The VNUS company introduced a completely new and different thermal ablation catheter in 2008. This was called the ClosureFast catheter—named because it was much faster than the old radiofrequency closure catheter. With this catheter thermal ablation can be accomplished in about the same amount of time it takes to do thermal ablation with a laser catheter—one or two minutes.

The thermal ablation mechanism for the ClosureFast catheter is completely different than for the older radiofrequency catheter. The new catheter essentially has a miniature electric coil, similar to but much smaller than the tip of a curling iron, that generates heat as the catheter is removed, effectively cauterizing the vein that it passes through. The effect is identical to the mechanism that occurs with endovenous laser treatment. The main difference between the two techniques is the manner in which energy is supplied to the tip of the catheter for the thermal ablation. The ClosureFast catheter uses electrical energy, while the laser catheter uses light energy. The VNUS company was purchased by Covidien in 2011, which now markets the VNUS products.

Venous laser ablation

The third thermal ablation technique makes use of a more recent technical development—that of the laser. This procedure, which is known as Endovenous Laser Treatment (EVLT) or Endovenous Laser Ablation Treatment (EVLAT), involves passing a laser optic fiber into the vein and heating the vein with laser energy. While this technique also damages the vein, it does so much more quickly than the original radiofrequency closure technique. Typically, treatment of the entire vein only takes about a minute or so, although it can take thirty to sixty minutes of preparation to prepare for the actual treatment.

There are several different types of laser treatments available, and they differ according to the wavelength—or color—of the laser. The original laser, which we use, has a wavelength of 790 nanometers—and has a reddish color. Other types of laser have been used that have wavelengths of 810, 910, 980, 1470, and 1560 nanometers. The higher wavelength lasers are in the infrared spectrum and aren’t visible to the human eye.

Why the variety of different laser wavelengths? Various manufacturers claim that their particular wavelength offers clinical advantages (such as less pain), or theoretical advantages (such as the particular wavelength exciting water molecules as opposed to hemoglobin molecules). Excellent results are routinely achieved with any and all of the various wavelength lasers.

Steam ablation

The third technique is still considered investigational, and involves a very old technology—-steam. With this approach a catheter is placed in the vein, and the vein is heated by either injecting hot steam into the catheter or by injecting water that is then converted to steam by a small heating element in the tip of the catheter. It appears that this technique, while probably being just as safe and effective as both Laser and Radiofrequency ablation, offers no particular advantage over these two procedures.

Abrasion ablation

Another technique, also still in the investigational stage, involves a catheter that damages the inner lining of the veins mechanically with small blades on the end of the catheter. It is recommended that the device be used in conjunction with a sclerosant, which is injected into the vein at the conclusion of the abrasion. This approach has the advantage in that it is less complex—no laser, radio frequency generator, or steam generator is required. This procedure is probably as safe as the other forms of vein ablation, but it remains to be seen if the long term results of the procedure will be as good as the other forms of venous ablation.