Channeling in myocardium tissue through nanosecond pulsed laser photodisruption at visible and near-infrared wavelengths

We investigated in vitro the mechanism of myocardium tissue ablation with nanosecond pulsed laser at the visible and near-infrared wavelengths. In experiments, porcine myocardium tissue was used as sample. It was found that the ablation rate at 1064 nm was larger than that at 532 nm in spite of lower absorption coefficient at 1064 nm than that at 532 nm for the tissue. During ablation the laser-induced optical emission intensity was measured and it was correlated with the ablation depth. Ablated tissue samples were fixed and stained, and histological analysis was performed with an optical microscope and a polarization microscope. For the 1064-nm laser-ablated tissues thermal damage was very limited, although damage that was presumably caused by mechanical effect was observed. The optical emission intensity during the 1064-nm laser ablation was higher than that during the 532-nm laser ablation at the same laser intensity. And for the 1064-nm laser ablation the ablation threshold was nearly equivalent to the optical emission. Based on these experimental results, we concluded that with the 1064-nm laser light, the tissue removal was achieved through a photodisruption process. Application of 1064-nm, nanosecond pulsed laser photodisruption to transmyocardial laser revascularization(TMLR) was discussed.