Myocardial infarction is the leading cause of death people in many countries over the world. Transmyocardial laser revascularization offers the possibility of a new method of treatment for patients who are not candidates for traditional bypass procedures and who do not respond to medical management for the treatment of myocardial ischemia and other coronary artery diseases [1]. Up to now mostly CO₂ laser was applied for this treatment. Some first results have been published also for CTH:YAG laser [2] but only a little work has been done in this field for Tm:YAG and Er:YAG wavelength. Therefore the objective of this study was to compare the ablation effect of chosen mid-infrared lasers (CTH:YAG, Tm:YAG and Er:YAG) with the myocardium tissue and compare this effect with the far infrared CO₂ laser radiation. For this purpose, the CTH:YAG, Tm:YAG and Er:YAG laser systems were designed, constructed and used for the interaction experiments. Besides those mid-infrared lasers, the commercially produced CO₂ laser (SYNRAD 57-1) was used for the comparative study. The results from the interaction experiment are following: the ablation coefficients were measured to be 0.029 mm/J for CTH:YAG laser radiation (2.10 micrometers, 1.8 J, 30 pulses); 0.061 mm/J for Tm:YAG (2.01 micrometers, 0.6 J, 30 pulses); 0.75 mm/J for CO₂ (10.6 micrometers, 2 J, 10 kHz, 1 burst), and 10.5 mm/J for Er:YAG (2.94 micrometers, 2 J, 1 pulse). From the histological examination follows that only the channels ablated by Er:YAG laser radiation are without any thermal damage of the surrounding tissue and with the minimal mechanical injury. As a conclusion - Er:YAG laser could be considered as a good candidate for the TMR besides CO₂ laser.

References

[2] Sundt,T.M. - Carbone,K.A. - Oesterle,S.N. - Robbins,R.C.: The Holmium:YAG laser for transmyocardial laser revascularization: initial clinical experience Am.Heart Ass. Ann.Meeting, New Orleans, NY, USA, pp. 385-395,1990

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