Transmyocardial laser revascularisation has no beneficial effect on high energy phosphates and lactate content during acute myocardial ischaemia in pigs

Objective: Transmyocardial laser revascularisation (TMLR) is used to treat endstage coronary heart disease. There is evidence that angina is significa ntly reduced after TMLR. However, the precise mechanism by which symptoms d isappear remains unknown. The objective of the present study was to examine the potential effects of TMLR on high-energy phosphates and myocardial per fusion in an acute ischaemic model. Method: Five male landrace pigs (42 +/- 1.8 kg) had TMLR of the anterolateral wall of the left ventricle using a 1 000 W CO2 laser (PLC, USA). Thereafter the anterior descending coronary art ery was occluded with a tourniquet. After 90 min of ischaemia, drill-biopsi es were taken from ischaemic and non-ischaemic areas as well as from laser channels. The specimens were snap-frozen in liquid nitrogen. Subsequently, methylene blue was injected into the left atrium to study tissue distributi on. The hearts were excised and the patency of channels was examined visual ly. Results: Coronary artery occlusion resulted in immediate blue discolora tion in both TMLR and control areas. There was no subendocardial methylene blue staining around laser channels. Inspection of hearts showed occlusion of laser channels due to thrombus formation at both endo- and epicardial le vels. ATP-metabolites significantly increased in ischaemic areas compared t o non ischaemic areas. Furthermore there was significant upregulation of pu rine-content in ischaemic regions even in areas with laser channels. Conclu sions: In our acute model there was early occlusion of the channels after T MLR. We suggest that clinical improvement after this procedure is not due t o increased myocardial oxygen delivery, since high energy phosphate levels and lactate content remained unchanged. (C) 1999 Elsevier Science B.V. All rights reserved.