The Science of Laser Lead Extraction or Removal
What is Laser?
Light Amplification by Stimulated Emission of Radiation.
What is Photoablation?
Photoablation is the use of ultraviolet laser light to break down and remove matter.
The Spectranetics CVX-300® Excimer Laser System generates 308 nanometers (nm) laser energy by electrically charging two gases, Xenon and Chloride (XeCl). The laser energy is transmitted along flexible fiber-optic strands encased in catheters and sheaths, which are passed through arteries and veins. The ultraviolet light energy is focused on the cardiovascular lesion or tissue requiring treatment. This process is called photoablation.
In peripheral vascular intervention, Spectranetics’ excimer laser system uses ultraviolet light to ablate blockages associated with peripheral arterial disease above and below-the-knee and to treat multiple morphology lesions comprising atheroma, fibrosis, calcium, and thrombus.
The Spectrum of Light
Laser light emitted from the Spectranetics laser is in the blue, or ultraviolet, spectrum at 308nm – similar to laser light employed for LASIK at ~193nm. As light moves toward the red spectrum it increases in temperature.
Mechanisms of Action: How Does Photoablation Work?
Excimer laser light is delivered to the tissue through a fiber-optic catheter. In a liquid environment, three mechanisms contribute to the ablation process: photochemical, photothermal and photomechanical. Transfer of the photothermal energy leads to vaporization.
1. Photochemical: 2. Photothermal: , 3. Photomechanical:
Dissolving Molecular Bonds Produces Photothermal Energy Creating Kinetic Energy
1. Vaporizing Molecular Bonds
- The laser light pulse targets the tissue for 135-billionths of a second.
- The laser light expands to a penetration depth of 50 microns, allowing the catheter or sheath to provide focused, controlled ablation on the tissue it contacts.
- The laser energy breaks down the tissue into particles, most of which are smaller than a red blood cell.
- Sub-cellular sized material is easily absorbed by the bloodstream to be carried out of the body, minimizing the risk of distal embolization.
2. Producing Photothermal Energy
- Absorption creates molecular vibration in molecules through heating of intracellular (inside the cell) water.
- The water vaporizes, rupturing cells. This process creates gaseous byproducts that produce a vapor bubble. All of this occurs within 100-millionths of a second, thereby limiting heat build-up in surrounding tissue.
3. Creating Kinetic Energy
- The fast expansion and implosion of the vapor bubble produces cavitation and pressure effects that further break down tissue and assist in sweeping ablated debris from the tip of the catheter.
- Debris byproducts consist of water, hydrocarbons (gases) and small
Timeline of a Single Pulse
- 135 100 400
- Billionth Millionths Millionths
- a second of a second of a second
- Bond Thermal Kinetic
- Dissolves Energy Energy 25 Thousandths of a second at 25 Hz: Resting Period
Pulse Rate = Number of times a laser pulses per second =Hz
- Pulsed technology in the ultraviolet spectrum combines secondary cavitation bubbles, which can form after the implosion of the first vapor bubble, further assisting tissue ablation.
- The entire process (per pulse) is over in approximately 0.5 milliseconds, and the next pulse arrives 25 milliseconds later.