Success of transmyocardial laser revascularization is determined by the amount and organization of scar tissue produced in response to initial injury: results of ultraviolet laser treatment.
OBJECTIVE
Previous studies of transmyocardial laser revascularization have reported open channels after ultraviolet laser treatment and closed channels with infrared lasers. We speculated that differences in long-term channel patency were determined by the healing response to injury.


METHODS
Channels were made in rat hearts with a frequency-tripled neodymium:YAG laser, at 5 and 10 mJ per pulse, by advancing an optic fiber through the myocardium, from the epicardium to the ventricular cavity. Several months later, we challenged the ability of the channel to supply blood by arterial occlusion and examined the channel structure with polarized light microscopy.


RESULTS
Low-pulse energy was associated with lower patency, more fibrosis, and larger infarcts than was the higher energy. Open channels were surrounded by collagen fibers aligned parallel to the channel; in closed channels, fibers were aligned perpendicular to the original channel direction.


CONCLUSIONS
The amount of initial injury and its repair determine channel patency and function.
D000818:Animals; D002921:Cicatrix / Q000209:etiology / Q000473:pathology*; D003326:Coronary Circulation; D005260:Female; D005355:Fibrosis / Q000209:etiology; D066298:In Vitro Techniques; D007259:Infrared Rays; D053685:Laser Therapy / Q000009:adverse effects / Q000379:methods*; D017202:Myocardial Ischemia / Q000601:surgery*; D009204:Myocardial Revascularization / Q000379:methods*; D009206:Myocardium / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014466:Ultraviolet Rays; D014654:Vascular Patency; D014945:Wound Healing