METHODS AND RESULTS: Anesthetized, open-chest rabbits received 30 min coronary artery occlusion/3 hrs reperfusion. Before CAO rabbits were randomized to
heliox (30%
oxygen + 70%
helium, n=8) or air supplemented with
oxygen to achieve blood gas values within physiologic range (n = 8). Rabbits received the appropriate mix during ischemic and reperfusion periods.
Infarct size (% risk zone) and no-reflow defect were measured at the end of the reperfusion period. The ischemic risk zone was similar in both groups (28% of left ventricle in
heliox and 29% in control).
Heliox breathing did not reduce
necrosis;
infarct size, expressed as a percentage of the risk region was 44±4% in the
heliox group and 49±5% in controls, p = 0.68. The extent of the no-reflow defect was not altered by
heliox, either expressed as a percent of the risk region (29±4% in
heliox and 28±3% in control) or as a percent of the necrotic zone (65±5% in
heliox and 59±8% in control).
Heliox treatment had no effect on hemodynamic parameters or arterial blood gas values.
CONCLUSION: Continuous
heliox breathing does not appear to be cardioprotective in the setting of acute
myocardial infarction in the rabbit model.
Heliox respiration administered during 30 minutes of
ischemia and 180 minutes of reperfusion did not alter
infarct size or the extent of no-reflow.