Saline vs. Contrast in Laser Angioplasty
Saline infusion should be used instead of contrast or blood during excimer laser coronary angioplasty to dramatically reduce the risk of coronary artery dissections and improve procedural safety. 1
The Critical Problem with Blood and Contrast
Blood (hemoglobin) and angiographic contrast media strongly absorb excimer laser light at 308 nm wavelength. 2 Upon absorption, this laser energy converts into rapidly expanding and imploding cavitation bubbles that generate intense pressure pulses, causing severe acoustomechanical trauma to the vessel wall. 2, 1 This mechanism is responsible for the morphologically unusual and severe dissections that occur during laser angioplasty when performed in a blood medium. 2
Evidence for Saline Superiority
Dissection Reduction
- Randomized controlled trial data demonstrates that intracoronary saline infusion reduces significant dissections (grade ≥2) from 24% to only 7% (p < 0.05). 1
- The mean dissection grade after laser angioplasty with saline infusion was 0.43 ± 0.13 compared with 0.91 ± 0.26 in blood medium. 1
- Animal studies confirm saline flush drastically reduced dissection incidence from 11/12 to 2/12 procedures (p < 0.002). 3
Mechanism of Benefit
- Saline infusion displaces blood from the ablation field, minimizing blood irradiation and consequent vapor bubble formation. 1
- By removing the absorptive medium (blood/contrast), saline creates an optical window that allows more direct and controlled laser energy delivery to the target tissue. 3
Practical Implementation
Injection Protocol
- Prewarmed normal saline should be injected through the coronary artery guide catheter at a rate of 1 to 2 mL/s using a power injector during laser pulse delivery. 1
- Saline is administered via the guidewire channel at approximately 0.2 mL/s during laser ablation. 3
- The technique involves delivering laser pulses in bursts (typically 3-second bursts) with continuous saline infusion. 3
Safety Profile
- No significant complications have been associated with saline infusion during excimer laser coronary angioplasty. 1
- The technique has resulted in improvements in both angiographic and clinical outcomes. 2
Important Caveats
Trade-offs with Saline Use
- While saline dramatically reduces dissections, it may increase the extent of medial and adventitial necrosis due to direct ultraviolet light irradiation of the arterial wall (no longer protected by blood absorption). 3
- At vessel edges where saline flush is less effective, intimal hyperplasia and arterial shrinkage can still occur at 8 weeks post-procedure. 3
- The middle-distal portions of treated segments show better outcomes with medial necrosis but without intimal hyperplasia formation. 3
Why Not Contrast?
- Contrast media, like blood, strongly absorbs 308 nm excimer laser light and produces the same problematic cavitation bubble formation. 2
- Using contrast during laser ablation would negate the safety benefits achieved with saline displacement of blood. 2
Bottom line: Intracoronary saline infusion should be incorporated into all excimer laser coronary angioplasty procedures as standard practice. 1