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?
We’ve looked at all of the wavelengths and fortunately I’ve had experience in the 810 nm, 940 nm, 980 nm, 1320 nm, and 1470 nm. As I mentioned before, the 810 nm, 940 nm, and 980 nm are basically hemoglobin-specific lasers. When we go up in wavelength to the 1320 nm and 1470 nm, that’s when we get to the water-specific lasers. It was the 1470 nm that showed an obvious reduction in pain and bruising. That is in comparison to the others in clinical and pilot studies.
You were the first in the United States to use a 1470 nm laser with a jacketed fiber. What can you tell us that made those unique cases better overall? What shocked you about using that the first time?
In our clinical comparison studies the combination of the 1470 nm and the NeverTouch fiber were far superior than just either one of them alone, so it’s not just the wavelength. It’s the combination of the wavelength and the NeverTouch fiber, which gave patients a better safety profile and easier recovery.
How many patients did you test this laser on? Can you give us any kind of statistics of the success rate with the new laser?
The 1470 nm that I’m using now with the NeverTouch fiber was FDA-approved about 4-5 months ago and I’ve now had more than 100 patients. The average follow-up time was approximately 72 days. My early success rate was 100% closure. I suspect that may decay as we go further. But understand that all of the wavelengths have been shown to work in terms of effectiveness in closure. It terms of closure, it’s really not the wavelength that we’re looking at. Whether it is an 810 nm or 1470 nm wavelength, they all work well for closure. It is the safety profile, the patient’s postoperative recovery, that we now focus on.
Would you say that most of your patients are in less pain with less bruising and they’re more satisfied with the results with this particular laser?
Yes, they seem to be giving accolades and I’ve been able to look at a few patients where I’ve used the hemoglobin-specific lasers with NeverTouch as well as the 1470 nm with NeverTouch. These patients were blinded and preferred the 1470 nm.
You have studied the differences between radiofrequency ablation and laser ablation.
What have you found in your studies?
When we first started, I was actually the first surgeon to use radiofrequency in the United States. This was back in 1999. It was before I got involved in laser. Radiofrequency was far superior to our traditional stripping technique. Since then I’ve had the opportunity to work with both laser and radiofrequency systems. Radiofrequency was considered the standard in terms of offering less pain and bruising compared to laser. Indeed, that was true when we looked at the 810 nm laser and the bare-tip fiber. But when we started using the NeverTouch fiber, or jacketed fiber, the differences in terms of the safety profile diminished significantly. If you looked at an inferiority study, there seemed to be no difference statistically in terms of pain and bruising.
Now, in longer-term studies we’ve looked at laser and radiofrequency in terms of efficacy of closure. Laser seems to outpace closure by 1 or 2 percentage points. That means it’s slightly better, but when you are talking in the neighborhood of 95% or 97% efficacy, that’s excellent either way. We also have data on higher wavelengths and the NeverTouch versus radiofrequency. When we looked at radiofrequency versus a 1470 nm wavelength laser, they were pretty much identical in a pilot study, and this involved approximately 50 patients in each cohort.
Is there anything further that you would like to add that wasn’t mentioned?
Yes. At the end of the day I find a laser system is the more intellectual piece of equipment when compared to radiofrequency. With laser you have the ability to tailor your treatment to nearly any vein problem or size. The laser system can keep up with your skill level and expertise. Currently radiofrequency offers less versatility and flexibility.
Both have made a world of difference in terms of patient care and patient outcomes in comparison to stripping. But when it comes to differences that influence my own use, I tend to use laser more often because of its versatility. With radiofrequency, you need to have at least a 7 cm vein that you are going to occlude. With laser, you can do shorter segments, 1 cm, 2 cm, etc. With radiofrequency, basically what you see is what you get and you don’t have freedom beyond that. You cannot really change the parameters on the radiofrequency delivery system, other than to repeat a treatment in the same segment. With laser, you can increase or decrease the power. You can deliver more or less energy in conformance with your clinical judgment on the size of the vein wall, or the diameter of the vein.
The laser also offers a smaller delivery system, so you can get in to smaller spaces. If you need to treat perforators, the laser procedure is simpler than using RF.
Dr. Kabnick is Director of NYU Vein Center and associate professor of surgery in the division of vascular surgery at New York University Medical Center.