Intramyocardial Hemorrhage in Patients with Acute Myocardial Infarction Without Reperfusion Therapy: A Prospective Study.

Background and Aims: IMH commonly presents in STEMI patients receiving reperfusion therapy and is considered as an ischemic reperfusion injury. However, it is unclear whether IMH occurs in AMI patients without reperfusion therapy. Methods and Results: We prospectively enrolled 40 patients with STEMI and 41 patients with NSTEMI admitted to the CCU of the Second Xiangya Hospital of Central South University from April 2020 to November 2021, all of whom did not receive reperfusion therapy. In the STEMI group, 16 patients were detected with IMH by CMR. However, in the NSTEMI group, only 3 patients were detected. The incidence of IMH was significantly higher in patients with STEMI than NSTEMI (16/40 vs 3/41, P < 0.001). Among patients with STEMI, the incidence of IMH was not significantly different between patients who underwent primary percutaneous coronary intervention and those who did not (16/40 vs 27/65, P = 0.876). Patients in the spontaneous reperfusion group had a higher incidence of IMH than patients in the non-spontaneous reperfusion group (11/23 vs 5/17, P = 0.240). Similarly, in patients with STEMI who did not receive reperfusion therapy, the incidence of MACE was higher in the IMH-present group than in the IMH-absent group (5/16 vs 2/24, P = 0.063). Conclusion: The incidence of IMH is comparable in patients with STEMI with or without reperfusion therapy, but considerably higher than that in NSTEMI patients. Patients with STEMI can present with IMH even when infarct-related vessel flow is not restored.