Today there is no doubt that angina in patients with diffuse end-stage coronary artery disease can be treated effectively by transmyocardial laser revascularization (TMLR). But until now, the underlying mechanism of TMLR is a matter of debate. The aim of this study was to investigate the immediate changes in functional and metabolic parameters after the creation of TMLR channels. In 12 pigs the local myocardial function (pressure-wall thickness-loops), tissue oxygen partial pressure (PO(2)), and the left ventricular intramyocardial wall pressure (IMP) was investigated simultaneously. The left ventricle was divided into 3 areas. Ischemia was induced in regions 1 and 2 by interrupting the coronary blood flow via the left anterior descending artery for 30 seconds. Region 3 served as non-ischemic control region. Thirty minutes after creation of 15-20 TMR channels in region 1, we repeated the coronary occlusion in regions 1 and 2 followed by measurement of all parameters in the 3 regions. The TMLR-treated region 1 showed a better contractility, a higher tissue PO2 and a higher intramyocardial wall pressure during the post-TMLR coronary occlusion in 8 out of 12 pigs when compared with the pre-TMLR occlusion (p<0.05), whereas the untreated region 2 continued to show severe disturbances in myocardial contractility combined with a lower tissue PO(2) and lower IMP during ischemia. Our results suggest that a blood flow via the laser channels immediately after TMLR is principally possible. However, because the channels seem to occlude in the early postoperative phase, the long-term effects of TMLR are likely to be a result of other mechanisms.