Ischemic conditioning maneuvers reduce myocardial infarct size. However, infarct size reduction can first be assessed hours after established reperfusion. The present study tested the hypothesis that ST-segment elevation and its attenuation reflect cardioprotection by ischemic conditioning online. Pigs were subjected to regional myocardial ischemia/reperfusion (1 h/3 h). Ischemic conditioning was induced prior to ischemia either locally (preconditioning; IPC; n=15) or remotely (remote preconditioning; RIPC; n=21), or remotely during ischemia (remote perconditioning; RPER; n=18), or locally at reperfusion (postconditioning; POCO; n=9). Pigs without conditioning served as controls (PLA; n=29). Area at risk and infarct size were measured postmortem, and ST-segment elevation was analyzed in a V2-like electrocardiogram lead. All ischemic conditioning maneuvers robustly reduced infarct size (PLA 42 ± 11% of area at risk; IPC 18 ± 10%; RIPC 22 ± 12%; RPER 23 ± 12%, POCO 22 ± 11%). With PLA, ST-segment elevation was increased at 5 min ischemia, sustained until 55 min ischemia and further increased at 10 min reperfusion. IPC and RIPC did not impact on ST-segment elevation at 5 min ischemia, but attenuated ST-segment elevation at 55 min ischemia. With RPER, ST-segment elevation was not different from that with PLA at 5 min but attenuated at 55 min ischemia. POCO abolished the further increase of ST-segment elevation with reperfusion. Cardioprotection by ischemic conditioning is robustly reflected online by attenuation of ST-segment elevation.