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 myocardial infarction. In addition, the influence of TMLR on healthy myocardium was analyzed. Methods: The short-term effectiveness of TMLR was evaluated in 38 open-chest anesthetized pigs with (n = 18) or without (n = 20) acute LAD occlusion (observation period 6 hours): Six pigs served as controls (thoracotomy only). An additional six pigs had LAD occlusion only (ischemic group). A subsequent 12 pigs were treated by TMLR (CO₂) prior to LAD occlusion: Six pigs received one laser channel/cm² (group 1) and in six pigs two channels/cm² in the LAD territory (group 2) were performed. In addition, 14 pigs underwent TMLR without ischemia: Seven pigs received 1 channel/cm² (group 3) and seven pigs 2 channels/cm² (group 4). Patho-morphological assessment 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. laser 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). Furthermore, in the lased territories of laser groups 3 and 4 microscopic analysis 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 = ns) The myocardial water content-measurements (MWC) of the ischemia and laser group 1 were not different at the end of the experiment (p = ns). In contrast, laser groups 2, 3 and 4 revealed significantly higher MWC values compared to control (p = 0.036, p < 0.001, p < 0.001; respectively). Conclusions: This prolonged acute study demonstrates that preventive CO₂-laser revascularization significantly reduces the amount of necrosis in the area at risk. Histological examination supported the idea that some pigment gained access to the ischemic tissue via patent channels. In healthy myocardium, TMLR significantly increases myocardial water content and induces non-significant small ischemic and very small necrotic areas surrounding open laser channels.

Key words:

Transmyocardial laser revascularization - - Pathology - - Histology - - Ischemia - - Coronary disease

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