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

Background and Objective: Previous studies of transmyocardial laser revascu larization have reported open channels after ultraviolet laser treatment an d closed channels with infrared lasers. We speculated that differences in l ong-term channel patency were determined by the healing response to injury. Methods: Channels were made in rat hearts with a frequency-tripled neodymiu m: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 mont hs later, we challenged the ability of the channel to supply blood by arter ial occlusion and examined the channel structure with polarized light micro scopy. Results: Low-pulse energy was associated with lower patency, more fibrosis, and larger infarcts than was the higher energy. Open channels were surroun ded by collagen fibers aligned parallel to the channel; in closed channels, fibers were aligned perpendicular to the original channel direction. Conclusion: The amount of initial injury and its repair determine channel p atency and function. (C) 1999 Wiley-Liss, Inc.