Characterizing acute ischemia via ECG: A study of severity, extent, and spatial variability in myocardial infarction and non-infarction groups

Ischemic heart disease remains the leading cause of mortality worldwide. Its diagnosis largely relies on detecting dynamic changes in the ST segment of the electrocardiogram (ECG). However, alterations in other ECG waves and intervals have also been reported. One factor that is often overlooked is the presence of a prior myocardial infarction and its influence on the myocardial response to a new ischemic event. This study aimed to quantify the magnitude and temporal dynamics of ECG changes during acute myocardial ischemia and to evaluate how a previous infarction modifies these changes. Twelve-lead ECG recordings obtained before and during acute ischemia induced by percutaneous coronary intervention in one of the three major coronary arteries were analyzed. Dynamic heartbeat averages were computed to extract and track features related to ECG depolarization (QRS width, amplitude, and area) and repolarization (T-wave amplitude and area, ST-segment deviation and area, and T-to-QRS amplitude ratio). The results show that, beyond ST-segment deviation, multiple ECG markers evolve over time during coronary artery occlusion. Repolarization features showed earlier and more pronounced alterations than depolarization features, reaching approximately 37-fold and 23-fold changes at 4 minutes of occlusion compared with baseline, respectively. Males showed faster and more sustained ST increases (up to