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 revascularization (TMR) prior to acute coronary artery occlusion improves regional myocardial function and reduces the infarct size in animals with significant coronary collateral circulation. Whether the protective effect of TMR is due to perfusion through the laser-made channels, increased collateral flow or other mechanisms remains unresolved. The aim of this study was to investigate whether TMR performed prior to acute coronary artery occlusion could 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 the left ventricle 30 minutes prior to occlusion of the proximal LAD for 45 minutes. The other group (n=6) was subjected to transient ischemia of the same duration without previous TMR. Area at risk and infarct size were determined after sacrifice.


RESULTS
No significant difference was found in the infarct size between the two groups (69+/-2% in the TMR group versus 62+/-4% in the control group). However, the arrhythmic index during the period of ischemia was significantly lower in the TMR group (1.0+/-0.3 vs 8.3+/-2.2, p<0.001). Blood flow in LAD increased to a maximum of 135+/-6% of baseline level three 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 flow capacity, but reduced ischemia-related arrhythmias and increased coronary flow transiently.
Department of Cardiovascular Surgery, Institute for Experimental Medical Research, Ullevaal Hospital, University of Oslo, Norway.
O
O
Tjomsland
F
F
Grund
G K
GK
Kanellopoulos
K
K
Kvernebo
A
A
Ilebekk
D000818:Animals; D003097:Collateral Circulation; D003326:Coronary Circulation; D004195:Disease Models, Animal; D005260:Female; D006439:Hemodynamics; D053685:Laser Therapy / Q000379:methods*; D008297:Male; D009203:Myocardial Infarction / Q000473:pathology / Q000517:prevention & control; D017202:Myocardial Ischemia / Q000517:prevention & control*; D009204:Myocardial Revascularization / Q000379:methods*; D014693:Ventricular Fibrillation / Q000209:etiology