Introduction:
Acute myocardial infarction (MI) is usually associated with ischaemic abnormalities in electrocardiography (ECG). However, a considerable proportion of MI cases present with no ischaemic changes (NIC). The exact impact of the ECG pattern and a culprit lesion on long-term outcomes in the era of routine percutaneous coronary interventions remains unclear.

Aim of the research:
To analyse baseline characteristics and 12-month outcomes of MI patients with various ECG patterns on admission as well as the exact impact of a culprit lesion on the long-term prognosis.

Material and methods:
Based on PL-ACS Registry data, we analysed patients admitted to Polish hospitals in 2015–2020 due to MI. A total of 111,689 cases who underwent primary percutaneous coronary intervention were included in the study. Based on initial ECG, 5 groups were established: ST segment elevation (STE), ST segment depression (STD), T-wave inversion (TWI), other ST-T abnormalities (STT), and no ischaemic changes (NIC).

Results and conclusions:
NIC patients accounted for over 10% of all MI cases. In-hospital mortality in NIC was higher than TWI but lower than in STE, STD, and STT. In 12-month follow-up NIC had worse prognosis than TWI and STE. STT and STD presented with the worst prognosis, which is associated with adverse factors like comorbidities, heart failure, and multi-vessel coronary disease. The impact of a culprit lesion on 12-month outcomes was equal for right coronary artery (RCA), obtuse marginal branch (OM), diagonal (D), and circumflex artery (Cx), i.e. it is negligible except for both LM and LAD.