The benefits of supplementary oxygen administered to patients with a non-complicated myocardial infarction have not been fully investigated, particularly in relation to the ageing myocardium. The effect of low and high pO2 levels in a young and aged rat papillary muscle work-loop model subjected to simulated ischaemia-reperfusion were investigated.
Papillary muscles from young (3months) or aged (12months) rats were subjected to simulated ischaemia-reperfusion injury (SIR) with high pO2 (∼390mmHg) (SIRhigh) or SIR with low pO2 (∼160mmHg) (SIRlow) during reoxygenation. Active work loops were performed at 5 minute intervals and subjected to 35minutes hypoxia followed by 95minutes reoxygenation. Muscle performance and recovery were calculated as a percentage ± S.E.M of the mean power output.
SIRhigh significantly (P < 0.001) improved the functional recovery of both young and aged papillary muscle when compared to SIRlow. In aged papillary muscle the mean improvement in power output between SIRhigh and SIRlow was lower (11.7% ± 0.7) than in young papillary muscle (19.6% ± 1.1). Young papillary muscle produced significantly higher normalised stress and power output (P < 0.01) when compared to aged papillary muscle.
This is the first study, using the work loop technique, to show that supplementary oxygen during reoxygenation significantly improves functional recovery of both young and aged papillary muscle. A significant difference was observed in functional recovery, normalised stress and power output between young and aged rat papillary muscles, with young papillary muscle recovering to a greater degree than aged papillary muscle following SIR.