Endovascular laser ablation therapy (EVLT)
Endovenous laser ablation (EVLA) and radiofrequency ablation have become the preferred minimally invasive treatments for superficial venous reflux disease, yielding initial closure rates of 95–100%. EVLA, in particular, demonstrates durable outcomes with a persistent closure rate of 94–97%.
EVLT related terminology
| Term | Definition |
|---|---|
| LASER Acronym | Light Amplification by Stimulated Emission of Radiation |
| Laser Characteristics | - Monochromatic - Coherent (in phase) - Collimated (near parallel direction) - Tightly focused (high power density) |
| Energy Units | - Laser energy: Joules (J) - Energy density: Joules per square centimeter (J/cm²) - Power: Watts (W) - Power density: Watts per square centimeter (W/cm²) |
| Irradiance | Power of light emitted divided by beam cross-sectional area (W/cm²) |
| Energy Fluence | Irradiance over unit time: (Laser power × Pulse duration) divided by laser beam cross-sectional diameter |
| Spatial Energy Fluence | Total energy dose during treatment: (Power × Number of pulses × Exposure time) divided by size of the treatment area (cm²) |
| Endovenous Fluence | Energy dose expressed as joules per centimeter of vein treated (J/cm) |
| Selective photothermolysis | Technique of applying a specific wavelength of light to target a specific chromophore for thermal ablation of a specific tissue structure. |
| Components of Laser System | - Lasing Medium - Resonating or Optical Cavity - Energy Supply - Delivery System (Optical Fibers or Mirrors) |
| Common Lasing Mediums | - Solids: Ruby, Nd-YAG - Gases: Helium, Chlorine, Argon, Krypton, Carbon Dioxide, Xenon - Organic Dyes: Rhodamine 6G - Semiconductors: Diode Lasers |
Other Keypoints:
| Laser Systems for EVLA | ||
|---|---|---|
| Type of Laser | Wavelengths (nm) | Optical Fiber Diameter (µm) |
| Diode Lasers | 810, 940, 980 | 500–600 |
| Nd:YAG Lasers | 1064, 1320 | 500–600 |
| Laser–Tissue Interactions | ||
| Interaction Type | Description | |
| Photochemical Reactions | Light energy causes chemical reactions, resulting in oxygen-free radical generation and tissue damage. | |
| Photothermolysis | De-excitation energy is released as heat, causing tissue damage through protein denaturing, coagulation, and necrosis. | |
| Mechanism of Action Theories for EVLA | ||
| Theory | Description | |
| Steam Bubble Theory | Initial proposal suggesting thermal injury via steam contact with vein wall, resulting in thrombotic closure. | |
| Direct Contact Theory | Emphasizes the role of direct contact between laser fibre and vein wall, leading to thermal injury and fibrosis. | |
| Fibrotic vs. Thrombotic Vein Closure | ||
| Closure Mechanism | Characteristics | |
| Fibrosis | - Clinical presentation: Minimal pain, erythema, swelling - Sonographic appearance: Hyperechoic, reduced diameter | |
| Thrombosis | - Clinical presentation: Significant pain, erythema, swelling - Sonographic appearance: Hypoechoic, expanded lumen | |
2. Sclerotherapy: Treatment of Varicose and Telangiectatic Leg Veins 6th edition