Effects of delayed remote limb ischemic preconditioning on myocardial injury in patients undergoing cardiac valve replacement under cardiopulmonary bypass

Abstract

Objective To evaluate the effects of delayed remote limb ischemic preconditioning (DRLIP) on myocardial injury in patients undergoing cardiac valve replacement under cardiopulmonary bypass (CPB). Methods A total of 41 patients of both sexes, aged 55-70 yr, weighing 50-75 kg, scheduled for elective cardiac valve replacement under CPB, of ASA physical status Ⅱ or Ⅲ(NYHA Ⅱ or Ⅲ), were randomly divided into 2 groups using a random number table: control group (group C, n=20) and group DRLIP (n=21). In group DRLIP, the patients underwent three 5-min cycles of unilateral lower limb ischemia, induced by a manual cuff-inflator placed on the left thigh and inflated to 200 mmHg starting from 24 h prior to surgery. Blood samples were taken from the central vein before aortic clamping, at 6 h of reperfusion and at 24 h after surgery for determination of plasma cardiac troponin I concentrations. Before aortic clamping and at the end of CPB, myocardial tissues were obtained from the right auricle for determination of the expression of caspase-3 and cell apoptosis. Apoptotic index was calculated. The recovery of spontaneous heart beats was recorded. Results Compared with group C, plasma troponin I concentrations were significantly decreased at 6 h of reperfusion, and the expression of caspase-3 was down-regulated, apoptotic index was decreased at the end of CPB, and no significant change was found in the incidence of recovery of spontaneous heart beats in group DRLIP. Conclusion DRLIP can protect myocardium against injury in the patients undergoing cardiac valve replacement under CPB, and inhibition of cell apoptosis is involved in the mechanism. Key words: Ischemic preconditioning; Cardiopulmonary bypass; Heart valve prosthesis implantation; Myocardial injury