Pathomorphological and histological analysis of the indirect revascularization method

Objective: This experimental study was initiated to determine whether TMLR may prevent porcine myocardium from ischemia and necrosis after acute myoca rdial infarction. In addition, the influence of TMLR on healthy myocardium was analyzed. Methods: The short-term effectiveness of TMLR was evaluated i n 38 open-chest anesthetized pigs with (n = 18) or without (n = 20) acute L AD occlusion (observation period 6 hours): Six pigs served as controls (tho racotomy only). An additional six pigs had LAD occlusion only (ischemic gro up). A subsequent 12 pigs were treated by TMLR (CO2) prior to LAD occlusion : Six pigs received one laser channel/cm(2) (group 1)and in six pigs two ch annels/cm(2) in the LAD territory (group 2) were performed. In addition, 14 pigs underwent TMLR without ischemia: Seven pigs received 1 channel/cm(2) (group 3) and seven pigs 2 channels/cm(2) (group 4). Pathomorphological ass essment and histology were performed. Results: TMLR limits the expansion of the myocardial infarction zone: laser group 2 demonstrated a significantly smaller area of necrosis in the area at risk (ischemic group (32%) vs. las er group 1 (18%, p = ns) and 2 (8%, p = 0.0076); laser group 1 vs. 2, p = 0 .0056). The amount of the area of necrosis of laser groups 3 (0.4%) and 4 ( 0.04%) compared to control (0%) did not differ significantly (p = ns). Furt hermore, in the lased territories of laser groups 3 and 3 microscopic analy sis revealed signs of ischemia in 10 +/- 30.9% of all examined histolocical samples (p = ns vs. control). During a short coronary occlusion the laser- induced tracks were partially filled with blue dye in 94.8 +/- 27.0/85.9 +/ - 34.3/94.85 +/- 22.0%/70.21 +/- 47.0% (laser groups 1-4 respectively p = n s) The myocardial water content-measurements (MWC) of the ischemia and lase r group 1 were not different at the end of the experiment (p = ns). In cont rast, laser groups 2, 3 and 4 revealed significantly higher MWC values comp ared to control (p = 0.036, p < 0.001, p < 0.001; respectively). Conclusion s: This prolonged acute study demonstrates that preventive CO2-laser revasc ularization significantly reduces the amount of necrosis in the area at ris k. Histological examination supported the idea that some pigment gained acc ess to the ischemic tissue via patent channels. In healthy myocardium, TMLR significantly increases myocardial water content and induces non-significa nt small ischemic and very small necrotic areas surrounding open laser chan nels.