The Effects of β Blockade and Partial Agonist Activity during Myocardial Ischemia

Myocardial protection with oxygenated esmolol cardioplegia during prolonged normothermic ischemia in the rat

“…It is likely that part of the protective mechanism of esmolol cardioplegia involves maintenance of high-energy phosphates by rapid reduction of energy demands. ␤-Blockers, administered either before or just after ischemia, have been shown in numerous animal models [1][2][3][4] to exert beneficial effects on ischemic myocardium. Although the mechanism for these benefits are unknown, speculations include improved balance between oxygen supply and demand by reducing oxygen demand through negative inotropic and chronotropic actions, 5,35 increased oxygen supply as a result of increased blood flow to ischemic areas, 35 and redistribution of blood flow from the subepicardium to the subendocardium.…”

“…Esmolol cardioplegia may provide an efficacious alternative to hyperkalemia. N umerous experimental and clinical studies have demonstrated that ␤-adrenergic antagonists (␤-blockers) can attenuate the extent of myocardial injury during ischemia and reperfusion, [1][2][3][4] although the mechanism of the cardioprotective efficacy of these drugs during myocardial ischemia is not completely understood. Possible mechanisms include decreasing heart rate and contractility (with a reduction of myocardial oxygen consumption), 5 decreasing sympathetic tone, 6 altering myocardial substrate use, 7 stabilizing cell membranes, 8 and reducing lipid peroxidation of membrane phospholipids.…”

Effect of esmolol on myocardial protection in pediatrics congenital heart defects

“…Many experiments and clinical studies indicate that β-adrenergic antagonists (β-blockers) can reduce the extent of the myocardial ischemia and reperfusion. [ 8 9 10 11 ] Although effective mechanisms of these medicines in myocardial ischemia are not completely clear, some possible mechanisms include decreasing heart rate and contractility (by reducing myocardial oxygen consumption),[ 12 ] decreasing sympathetic tonicity,[ 13 ] changes in myocardial substrate consumption,[ 14 ] stability of the cell membranes,[ 15 ] and reducing peroxidation of phospholipids of the membrane. [ 16 ]…”

“…Administration of the β-blockers contributes to myocardial protection during cardiac surgery via hypothermic arrest. [ 8 9 10 11 ] However, β-blockers are avoided in CPB because they are considered as a negative inotrope and may cause difficulty in terminating CPB. [ 17 ] Esmolol is metabolized rapidly by the arylesterase in blood, so its half-life is only 9 min.…”