RIPC Remains a Promising Technique for Protection of the Myocardium during Open Cardiac Surgery: A Meta-Analysis and Systematic Review.

Background: Remote ischemic preconditioning (RIPC) is the process of inducing brief ischemia in a tissue to prevent ischemic damage in another. This preconditioning can be induced simply by inflating a blood pressure cuff on a limb. Previous randomized controlled trials (RCT) have suggested that RIPC may infer myocardial protection during open cardiac surgery. One method of assessing the degree of myocardial damage incurred in these studies is to assay troponin concentration. Troponin is a cardiac enzyme released by damaged myocardiocytes. With the recent publication of several large RCTs in this area, a meta-analysis of the evidence was undertaken.

Methods: A systematic search of PubMed, EMBASE, and clinicaltrials.gov.uk was conducted using MeSH terms "ischaemic preconditioning" and "cardiac surgery." RCTs that examined post-surgery troponin concentrations were included in this review. The primary outcome investigated was troponin levels at six hours post-cardiac surgery. Secondary outcomes included six to eight hour and twenty-four hour troponin release.

Results: Thirteen RCTs, comprising 1398 participants, were identified for inclusion in this meta-analysis. Twelve hour postoperative troponin was significantly reduced by RIPC, standardized mean difference 1.29 (95% CI 0.34-2.24). Six to eight and twenty-four hour troponin were also significantly reduced, standardized mean differences 1.23 (95% CI 0.62-1.84) and 1.25 (95% CI 0.31-2.19) respectively.

Conclusions: The reduction in troponin concentration suggests that RIPC reduces myocardial damage during open cardiac surgery, however, the degree of bias in the studies assessed may have had a significant impact on this result.