Transmyocardial laser induces coronary hyperemia and reduces ischemia-related arrhythmias, but fails to delay development of myocardial necrosis after coronary artery occlusion in pigs

Background. Several investigators have reported that transmyocardial revasc ularization (TMR) prior to acute coronary artery occlusion improves regiona l mycardial function and reduces the infarct size in animals with significa nt coronary collateral circulation. Whether the protective effect of TMR is due to perfusion through the laser-made channels, increased collateral flo w or other mechanisms remains unresolved. The aim of this study was to inve stigate whether TMR performed prior to acute coronary artery occlusion coul d offer protection from ischemic injury in the pig, an animal with Limited native collateral coronary circulation. Methods. In one group (n = 4), TMR was performed in the anterior wall Of th e left ventricle 30 minutes prior to occlusion of the proximal LAD for 45 m inutes. The other group (n=6) was subjected to transient ischemia of the sa me duration without previous TMR. Area at risk and infarct size were determ ined after sacrifice. Results. No significant difference was found in the infarct size between th e two groups (69 +/- 2% in the TMR group versus 62 +/- 4% in the control gr oup). However, the arrhythmic index during the period of ischemia was signi ficantly lower in the TMR group (1.0 +/- 0.3 vs 8.3 +/- 2.2, p < 0.001). Bl ood flow in LAD increased to a maximum of 135 +/- 6% of baseline level thre e minutes after the end of the TMR procedure. Conclusions. TMR failed to reduce the infarct size following acute coronary artery occlusion in the pig, an animal with a small collateral coronary no w capacity, but reduced ischemia-related arrhythmias and increased coronary now transiently.