The Effect Of Lipopolysaccharide On Ischemic-Reperfusion Injury Of Heart: A Double Hit Model Of Myocardial Ischemia And Endotoxemia

Introduction: Myocardial ischemia may coincide and interact with sepsis and inflammation. Our objective was to examine the effects of bacterial endotoxin on myocardial functions and cell injury during acute ischemia.Methods: Rabbits were pretreated with incremental doses of E. Coli lipopolysaccharide (LPS) or normal saline. Myocardial ischemia was induced by 50-minute occlusion of left anterior descending artery. S-TNFaR was additionally used to block the effects LPS.Results: Ventricular contractility as it was measured by dp/dt during systole decreased from 2445 +/- 1298 to 1422 +/- 944 mm Hg/s, P = .019. Isovolumetric relaxation time as an index of diastolic function was prolonged from 50 +/- 18 ms to 102 +/- 64 ms following ischemia. Pretreatment with low concentrations of LPS (<1 mu g) had no effect on dp/dt, while at higher concentrations it suppressed both contractility and prolonged IVRT. Cell injury as measured by cardiac troponin I level increased to 15.1 +/- 3.2 ng/dL following ischemia and continued to rise with higher doses of LPS. While blocking TNFa did not improve the myocardial contractility after ischemia, it eliminated additional deleterious effects of LPS.Conclusion: Lower doses of LPS had no deleterious effect on myocardial function, whereas higher doses of this endotoxin cause cardiac dysfunction and increased extent of injury.