Myocardial tissue ablation by single high-energy laser pulses for ELR and TMR

摘要

The objective of this study is to compare the ablation sites induced by two different laser and application systems for myocardial laser revascularization. One system used was an 800 W CO$-2$/ laser, which is clinically established for transmyocardial laser revascularization (TMR). The second system was a self-designed Holmium laser emitting single high energy pulses for the minimal invasive approach of endocardial laser revascularization (ELR), whereby the laser light is transmitted via optical fiber into the left ventricle to ablate the myocardial channels from the inside. The laser energy was applied to Polyacrylamide (PAA) as transparent tissue phantom and in water as blood phantom. The ablation dynamics were investigated by high speed flash photography recording a picture series of a single event. Reperfused ex- vivo porcine hearts were treated to quantify differences in the thermal-mechanical damage ranges by polarization light microscopy. Ablation dynamics in water revealed oscillatory changes of the axial length of the steam bubbles between 3 mm and 12 mm during the CO$-2$/ laser pulse. For the Holmium laser pulse a maximal axial and lateral length of 5 mm was observed. The lateral dimensions of the bubbles were maximal 1 mm with the CO$-2$/- and 3.5 mm with the Holmium laser system. In PAA bubbles also collapse during the laser pulse which affects the size of the ablated channels. Using 12 J Holmium laser pulses for ablation of PAA, channel depths around 7 mm were found. Single Holmium laser pulses demonstrate ablations comparable in size and thermal- mechanical collateral damage to those achieved with the standard CO$-2$/ laser. The results are very encouraging for single pulse ELR and demonstrate the potential of a catheter based minimal invasive procedure for laser heart reperfusion.