Transmyocardial laser revascularization in the acute ischaemic heart: no improvement of acute myocardial perfusion or prevention of myocardial infarction

Objective: Transmyocardial laser revascularization (TMLR) has been used to provide enhanced myocardial perfusion in patients not suitable for coronary revascularization or angioplasty. This study investigates the acute change s in myocardial perfusion after TMLR with a Holmium:Yttrium-Aluminium-Garne t (YAG) laser with a thermal imaging camera in a model of acute ischaemia, and confirms its midterm effects by post-mortem investigation of magnetic r esonance imaging and histopathological examination. Methods: Acute myocardi al ischaemia was induced by occlusion of the dominant diagonal branch in te n sheep. Perfusion measurements were undertaken first in the unaffected myo cardium, then after temporary occlusion of the coronary to obtain a control measurement for ischaemic myocardium. Myocardial perfusion was then evalua ted during reperfusion after release of coronary occlusion. Then the corona ry was permanently occluded and 20.5 +/- 2 channels were drilled with the H olmium:YAG laser and perfusion was measured again. The other four sheep ser ved as control with untreated ischaemia. All animals were sacrificed after 28 days following administration of gadolinium i.v. to serve as contrast me dium for magnetic resonance tomography. The hearts were subjected to magnet ic resonance tomography and histopathological examination. Results: Intraop erative perfusion measurements revealed a decreased perfusion after tempora ry occlusion and an increased perfusion in reperfused myocardium. After TML R, no improvement of myocardial perfusion above the ischaemic level could b e shown. Magnetic resonance images could neither confirm patent laser chann els nor viable myocardium within ischaemic areas. On histology no patent en docardial laser channel could be detected, The transmural features were myo cardial infarct with scar tissue. Conclusions: In the presented sheep model with acute ischaemia, TMLR with a Holmium:YAG laser did not provide acute improvement of myocardial perfusion as assessed by a thermal imaging camera . This would suggest no direct contribution of newly created laser channels to myocardial perfusion. As chronic effects are concerned, no perfused las er channels could be identified by later magnetic resonance imaging or hist ology. (C) 1999 Elsevier Science B.V. All rights reserved.