Effect of hyperoxic reperfusion on final infarct size after ST elevation myocardial infarction (STEMI) in old Wistar rats

Introduction Elderly people above 65 years old account for more than 80% of patients with ischemic heart disease [1] . Most of animal models of myocardial ischemia-reperfusion injury (IRI) involve young animals, with the assumption that findings are applicable to older animals and thus applicable to humans at highest risk, the elderly. Current studies failed to analyse the effect of hyperoxia during myocardial infarction (MI) reperfusion in old rodent model. Objective Assess the final myocardial infarct size after normoxic and hyperoxic MI reperfusion in old Wistar rats. Method STEMI was induced in old male Wistar rats (35–40 weeks old) by ligation of the left anterior descending (LAD) artery and maintained for 60 minutes. Animals were randomised either in the hyperoxic reperfusion (HR) group (receiving 100% oxygen) or the normoxic reperfusion (NR) group (21% of oxygen) for a 3-hour reperfusion. At the end of reperfusion, Evans Blue dye solution was injected to delineate the ischemic area from the non-ischemic area. The heart was cut into transverse slices and immerged in TTC solution. Myocardial infarct size was assessed in two ways; first troponin T concentration was measured after reperfusion, secondly ischemic zone and area at risk of the myocardium slices were measured by planimetry. Preliminary results A total of 8 rats underwent HR vs 11 NR. No difference was observed in the final myocardial infarct size between the two groups in both methods of myocardial infarct size assessment. Conclusion These very preliminary results corroborate the observations made in young animals’ studies [2] , [3] , however they should be taken cautiously since they are based on a very small cohort. There is a need to understand the effect of hyperoxic MI reperfusion as animal studies contradict the findings in human studies [4] .