CoolTouch physicians using the CTEV(TM) micro-pulsed laser reported 50% FEWER thromboembolic complications when compared to other heat ablation methods for endovenous ablation of varicose veins.

CoolTouch 1320nm CTEV Users Report 50% Fewer Complications from Thromboembolisms

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Endothermal Heat Induced Thrombosis (EHIT)

Lowell S. Kabnick, MD, FACS, FACPh Todd L. Berland, MD

Introduction

Endovenous ablation of the great saphenous vein (GSV) is the treatment modality of choice in the setting of symptomatic varicose veins. Endothermal Heat Induced Thrombosis (EHIT) of the GSV is an expected outcome, but what remains unclear is the clinical outcome of patients who present with this entity in close proximity or with extension into the common femoral vein. With an incidence in the literature ranging from 0% to 16% (1-3), this has gained the attention of physicians treating this disease process. Herein we describe a classification system and algorithm for treatment.

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Endovenous Ablation with Laser Induced Thrombolysis

David Hennings, MS; Craig Lindsay, Thomas Hennings; (CoolTouch Inc.), 2010

Purpose:

Thermally induced thrombus is common during endovenous ablation. Thrombus can absorb laser energy reducing efficiency of vein wall coagulation and can carbonize and explode causing vein wall perforations.

Proximal thrombus can break off into the venous system and intravenous thrombus can mask non- closed segments.

Background:

Pulsed mid-infrared lasers have been used since at least the 1980s for laser thrombolysis in the treatment of strokes (O. Topaz, The Quest for Laser Thrombolysis, Lasers Med Sci 2001). Lasers with pulse lengths from 10nsec to 10msec have been used to generate vapor bubbles that break up clots when they collapse. These same lasers will generate less thrombus in the presence of blood during an endovenous ablation procedure.

“Heating blood causes many changes in the erythrocytes, including cell shape modification, cell membrane rupturing, protein denaturation, aggregation, and blood gelation; which can all possibly contribute to coagulum formation.” (S. Mordon, Dynamics of Temperature Dependent Modifications of Blood in the Near-Infrared, Lasers in Surgery and Medicine 37:301-307 2005) “during laser treatment, fibrin develops through thermal alteration of fibrin complexes or proteolytic cleavage of fibrinogen. Laser treatment of cutaneous vascular disease causes intravascular consumption of fibrin-promoting factors.”

(Goldman et al, Sclerotherapy, Fourth Edition, Elsevier 2007)

Experimental Equipment:

1320 nm Nd:YAG Laser, Rep rate: 20, 50 Hz; Pulse length: 100, 300, 500,1000 µsec Power: 7 watts
1064 nm Nd:YAG Laser, Rep rate: 20, 50 Hz; Pulse length: 100 µsec Power: 7 watts
1470 nm Diode Laser, Continuous wave Power: 7 watts
810 nm Diode Laser, Continuous wave Power: 7 watts
940 nm Diode Laser, Continuous wave Power: 7 watts
980 nm Diode Laser, Continuous wave Power: 7 watts
1310 nm Diode Laser, Continuous wave Power: 7 watts
2100 nm THC:YAG Laser: Rep rate: 10 Hz; Pulse length 350 µsec Power: 7 watts
1320 nm CoolTouch CTEV Laser Rep rate: 50 Hz; Pulse length 150 µsec Power: 7 watts

Experimental Fibers:

550µm core Silica Clad (all silica) NA=.21; Low OH

550µm core Hard Plastic Clad NA=.37; Low OH

365µm core Silica Clad NA=.21; Low OH

Protected Tip (metal sleeve)

Encapsulated Tip (quartz capillary)

Experimental Methods:

15 ml of porcine blood in Sodium EDTA was placed in a 10 ml graduated cylinder. The room temperature and temperature of the blood was taken. All lasers were calibrated to operate at 7 watts. The laser fired in the blood for 30 seconds, while being pulled back at 0.5mm/sec for 10 trials. The fiber was introduced to the same depth for each trial. The temperature was taken after each trial, also at the same depth each time. Depending on the type of fiber, it was either wiped clean with a pre-tared KimWipe (the cap-tipped fibers) and then weighed; or it was clipped and the piece of fiber was weighed (the rest). The fiber piece was then cleaned and weighed. Its mass was subtracted from the original mass of fiber and coagulum to obtain the mass of just the coagulum. The fiber was also stripped and cleaved to produce a clean tip for the next trial. The graduated cylinder was stirred and inverted several times between each trial. If the fiber could not be clipped then the power of the laser was checked between trials as well. The leftover blood was saved for possible further analysis. Two bags of porcine blood were used. Data from each bag was separated as series 1or series 2 for analysis. Series 2 blood coagulated less than series 1.

Summary:

Continuous wave (CW) diode lasers generated coagulum on the fiber tip, regardless of laser wavelength.

Pulsed lasers with kilowatt peak powers did not generate coagulum on the fiber tip.

Protected tip or encapsulated tip fibers did not eliminate coagulum formation.

Conclusions:

Coagulum may be reduced by using:

~ Shorter pulse length

~ Higher energy per pulse

~ Smaller diameter fiber

~ 1320 nm laser

Fiber cladding design affects coagulum formation.

CoolTouch CTEV pulsed laser parameters of 150-300 usec, 20-50Hz, 365-550 fibers produces less coagulum.

Thrombus Formed

1320nm (pulsed) 980nm (cw)

550 µm Hard Plastic Clad Fiber NA = 0.37

Average Coagulum Mass vs. Wavelength of Laser - Series 1 blood

550 All Silica Fiber NA = 0.21

Average Coagulum Mass vs. Wavelength of Laser - Series 1 blood

550 All Silica Fiber NA = 0.21

Average Coagulum Mass vs. Wavelength of Laser – Series 2 blood

365 All Silica Fiber NA = 0.21

Average Coagulum Mass vs. Wavelength of Laser - Series 1 blood

550 All Silica Fiber NA = 0.21

Average Coagulum Mass vs. Wavelength of Laser – Series 2 blood

365 All Silica Fiber NA = 0.21

Average Coagulum Mass vs. Wavelength of Laser - Series 1 blood

365 All Silica Fiber NA = 0.21

Average Coagulum Mass vs. Wavelength – Series 2 blood

Av. Weight of Coagulum vs. Peak power Density – Series 1 blood

Pulsed 1320 nm Coagulum – All at 7 watts


CoolTouch CTEV Laser Parameters

Protected Tip Fibers

Av. Coagulum Mass vs. Wavelength of Laser – Series 1 blood

Percent Transmittance vs. Sample Number

Thrombus-related bibliography [PDF]

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