Exercise-induced ischemic preconditioning detected by sequential exercise stress tests: a meta-analysis

Exercise-induced ischemic preconditioning (IPC) can be assessed with the second exercise stress test during sequential testing. Exercise-induced IPC is defined as the time to 1 mm ST segment depression (STD), the rate-pressure product (RPP) at 1 mm STD, the maximal ST depression and the rate-pressure product at peak exercise. The purpose of this meta-analysis is to validate the parameters used to assess exercise-induced IPC in the scientific community. A literature search was performed using electronic database. The main key words were limited to human studies, which were (a) ischemic preconditioning, (b) warm-up phenomenon, and (c) exercise. Meta-analyses were performed on the study-specific mean difference between the clinical measures obtained in the two consecutive stress tests (second minus first test score). Random effect models were fitted with inverse variance weighting to provide greater weight to studies with larger sample size and more precise estimates. The search resulted in 309 articles of which 34 were included after revision (1053 patients). Results are: (a) time to 1 mm ST segment depression increased by 91 s (95% confidence interval (CI): 75-108), p < 0.001; (b) peak ST depression decreased by -0.38 mm (95% CI: -0.66 to -0.10), p < 0.01; and (c) rate-pressure product at 1 mm STD increased by 1.80 × 10(3)mmHg (95% CI: 1.0-2.0), p < 0.001. This is the first meta-analysis to set clinical parameters to assess the benefit of exercise-induced ischemic preconditioning in sequential stress testing. The results of this first meta-analysis on the sequential stress test confirm what is presented in the literature by independent studies on exercise-induced ischemic preconditioning. From now on, the results could be used in further research to set standardized parameters to assess the phenomenon.