The Protective Effects of Myocardial Ischemic Postconditioning on Cardiac Surgry: A Systematic Review and Meta-Analysis of Rats and Clinical Trials

Abstract

Background: Ischemic postconditioning (IPC) is a potent protective strategy implemented in animal myocardial ischemic-reperfusion (IR) models, while it has not yet been translated universally into clinical practice. We performed a unique systematic review and meta-analysis of animal and clinical studies respectively, to assess the protective effects of myocardial IPC and provide a new perspective for clinical practice. Methods: PubMed and Web of Science were searched for relevant researches. Trials met our inclusion criteria were selected and reviewed, and the meta-analyses were performed via Review Manager. Results: 44 trials were included in the meta-analysis. In animal studies, IPC demonstrated a decrease in size of myocardial infarction (standardized mean difference [SMD] -3.21, 95% confidence interval [CI] -3.89 to -2.52, P<0.00001), however, subgroup analysis showed that the protective effects of IPC disappeared in diabetic rats and hyperlipidemia rats (SMD -0.10, 95% CI -1.32 to 1.12, P=0.05; SMD -2.02, 95% CI -4.29 to 0.26, P=0.08, respectively). IPC reduced apoptosis index significantly (SMD -2.56, 95% CI -3.56 to -1.55, P<0.00001), while subgroup analysis indicted that IPC had no effect on decrease in level of myocardium apoptosis in hyperlipidemia rats (SMD -0.31, 95% CI -1.13 to 0.50, P=0.46). In clinical trials, no differences were noted in mortality between IPC and IR patients (SMD 0.44, 95% CI 0.07 to 2.85, P=0.41). IPC decreased the level of cardiac troponin I (cTnI) (SMD -1.74, 95% CI -2.71 to -0.78, P=0.0004), reduced the inotrope score (SMD -2.31, 95% CI -2.85 to -1.76, P<0.00001), shortened the time of ventilation and intensive care unit (ICU) stay (SMD -0.57, 95% CI -0.87 to -0.26, P=0.0002; SMD -0.57, 95% CI -0.84 to -0.30, P<0.0001, respectively). Conclusions: Myocardial IPC provided efficient protective effects for healthy rats rather than diabetic or hyperlipidemia rats. In clinical trials, IPC appeared to be beneficial to cardiac function and cardiac surgery prognosis, but had no effect on postoperative cardiac death.