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 significantly reduced after TMLR. However, the precise mechanism by which symptoms disappear remains unknown. The objective of the present study was to examine the potential effects of TMLR on high-energy phosphates and myocardial perfusion 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 1000 W CO2 laser (PLC, USA). Thereafter the anterior descending coronary artery was occluded with a tourniquet. After 90 min of ischaemia, drill-biopsies 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 distribution. The hearts were excised and the patency of channels was examined visually.

RESULTS

Coronary artery occlusion resulted in immediate blue discoloration 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 levels. ATP-metabolites significantly increased in ischaemic areas compared to non-ischaemic areas. Furthermore there was significant upregulation of purine-content in ischaemic regions even in areas with laser channels.

CONCLUSIONS

In our acute model there was early occlusion of the channels after TMLR. We suggest that clinical improvement after this procedure is not due to increased myocardial oxygen delivery, since high energy phosphate levels and lactate content remained unchanged.