Long-term outcomes in patients with acute myocardial infarction and no ischemic changes on electrocardiogram

•Up to 10% of patients with acute MI had no ischemic abnormalities (NIC) on ECG.•Their in-hospital mortality was higher than the group with T-wave inversion.•The long-term outcomes were equal to the ST-segment elevation group.•Diabetes and previous MI or revascularization therapy were associated with NIC. Acute myocardial infarction (MI) is commonly associated with ischemic abnormalities on electrocardiography (ECG). However, a significant proportion of patients present with no ischemic changes (NIC), and their baseline characteristics and management differ considerably from those with other ECG patterns. In the era of rapid troponin assays, the exact prognostic effects of normal ECGs remain unclear. This study aimed to compare the outcomes of patients with MI without ischemic changes and those with other ECG patterns. Between 2012 and 2018, 155,073 patients with MI were enrolled in the prospective nationwide Polish Registry of Acute Coronary Syndromes (PL-ACS). The patients were assigned to one of the following groups: NIC, ST-segment elevation (STE), ST-segment depression (STD), T-wave inversion (TWI), and other ST-T abnormalities (STT). The NIC group accounted for 9.56% of all patients. The in-hospital risk of death was lower in the TWI group than in the NIC group. In the STE, STD, and STT groups, the short-term results were substantially worse. During the 12-month observation period, TWI had the best prognosis. The worst long-term prognoses were associated with STT and STD. The outcomes of the STE and NIC groups were similar (12-month death rate 9.0% vs. 8.7%, respectively; P=0.534), despite the fact STE was an independent predictor of 12-month prognosis. The prognosis of patients with MI and NIC is not as favorable as previously thought. Their long-term outcomes were equal to those of the TWI and STE MI groups.