Cath Lab Digest

Listen to a clip of this interview at http://vasculardiseasemanagement.com/content/qa-dr-lowell-s-kabnick-md-a...

Tell me about the latest advances in endovascular laser therapy for varicose veins.

There have been 2 major advances in endovascular laser therapy for varicose veins. First is the advent of lasers using 1470 nm and other water-specific wavelengths. Second is the use of jacket-tip laser fibers.

Water-specific wavelengths target the water in the lining of the vein wall, which makes it more efficient. You need to deliver less energy and power to achieve the same results as achieved with hemoglobin-specific lasers that act on blood in the vein. The 1470 nm wavelength in particular has allowed us to have a better safety profile this way.

The second major advance is the new generation of fibers, specifically the jacket-tip, or covered fibers such as the NeverTouch fiber (AngioDynamics). They allow us to avoid contact with the vein wall. We started with bare-tip fibers. They had a poor safety profile, in terms of the fiber coming in contact with the vein wall and causing perforations. These perforations led to extravasation of blood, which then caused pain and bruising. With the new fibers, the tip is now recessed in a covered jacket. This adds to a physical property by increasing the diameter on a theoretical basis, which then allows the power density to be decreased. The power density is the energy that comes out of the laser light, in a focused beam. The wider the beam, the more the power density decreases, and the biological behavior of that fiber changes. This allows it to act like a coagulating fiber as opposed to a cutting fiber. Again, that decreases the potential for perforations and makes it safer. The combination of moving to the 1470 nm water-specific laser, and the NeverTouch fiber, has made these advances and the safety profile that much better.

What are some side effects that could affect patients that this particular model changes?

When we talk about safety profile, we’re really targeting the postoperative period and we’re looking at pain and bruising. That is, the ability of the patient to recover faster. We want less pain and bruising so we can achieve that. I’ve performed a great deal of research on this; as a matter of fact, there was an article published in Vascular Disease Management, which goes through much of this (Kabnik LS, March 2010, Vol. 7, E77–E81).

When we started out with the 810 nm laser, we had to use more power and a higher energy level. With power, we’re talking about watts. With energy, we’re talking about joules per centimeter. Together, they give the linear endovenous energy density, which is essentially the amount of energy we’re applying to the target. The 810 nm laser, which is a hemoglobin-specific laser, needed more energy and more power to get the veins to close. Therefore, it had the issues of equivalently more pain and bruising.

From that starting point we looked at different wavelengths: the 810 nm and 980 nm wavelengths. Then we jumped to 1320 nm and 1470 nm wavelengths, which are for water-specific lasers. We asked patients to indicate on a 10‐point analogue pain scale how much pain they felt. The bruising scores were out of a 5-point scale and involved digital pictures of a treated leg that was scored for bruising by a blinded nurse. By comparison, the pain and bruising seemed to decrease significantly when we used higher wavelengths.

We also looked at the bare-tip fiber versus the covered fiber. We looked at the covered fiber in combination with higher wavelengths, versus the alternatives. Again, the occurrence of pain and bruising decreased when you used the covered fiber and further still if you combined it with a higher wavelength.

What evidence is there that a jacketed laser fiber is better than a bare fiber?

Let’s start with the bare-tip fiber. The bare-tip fiber has been a cutting fiber and we’ve known that it produces more perforations in the vein wall, which leads to more black and blue ecchymosis and that triggers pain receptors. The jacket-tip fiber allows us to use a fiber to deliver the light source in a more spread-out fashion, which essentially decreases the power density. This is achieved with the NeverTouch in particular by placing a glass ferrule at the end of the bare-tip fiber. The addition of the glass ferrule increases the active diameter of the beam approximately 2 times, which decreases the power density approximately 56 times as compared to a bare tip. That changes the biological behavior and makes it a coagulating fiber as opposed to a cutting fiber. Around the ferrule-covered tip, a metallic-type jacket is placed, and the fiber is recessed inside that metallic jacket. That way the fiber never comes into contact with the vein wall to perforate it.

Is there a certain laser wavelength that you think is best?