OBJECTIVE When fibrinolysis fails in patients with ST elevation myocardial infarction, they are referred for a rescue percutaneous coronary intervention (PCI). However, there is still no evidence of how much myocardium potentially at risk we can actually salvage after rescue PCI. METHODS Fifty consecutive patients. Cardiac magnetic resonance was performed within 6 days. Myocardial necrosis was defined by the extent of abnormal late enhancement, myocardium at risk by extent of edema, and the amount of salvaged myocardium by the difference between myocardium at risk and myocardial necrosis. Finally, myocardial salvage index (MSI) resulted from the fraction (area-at-risk minus infarct-size)/area-at-risk. RESULTS The mean time elapsed between pain onset and fibrinolitic agent administration was 176 ± 113 min; time lysis-rescue=PCI 209 ± 122 min; time pain onset-PCI = 390 ± 152 min. The area at risk was 37% ± 13% and infarct size 34.5% ± 13%. Salvaged myocardium was 3% ± 4% and MSI 9 ± 8. Salvaged myocardium and MSI were similar between patients with the artery open on arrival at the catheterization lab (Thrombolysis in Myocardial Infarction [TIMI] 3) and those with TIMI flow ≤ 2 (3.3% ± 3.6% and 8.2 ± 6.9 in TIMI 0-2 vs 3.0% ± 3.7% and 10.8 ± 10.9 in TIMI 3; P=.80 and 0.31, respectively). No significant difference was observed between patients who went through rescue PCI within a shorter time and those with longer delay times. CONCLUSIONS The myocardial salvage after rescue PCI quantified by cardiac magnetic resonance is very small. The long delay times between pain onset and the opening of the infarct-related artery with PCI are most probably the reason for such a minimal effect of rescue PCI.