Relation of Total Ischemic Time to Repolarization Indices and Their Impact on Outcomes Among STEMI Patients Undergoing Primary PCI

ST-elevation myocardial infarction (STEMI) remains a time-critical cardiovascular emergency. Early reperfusion is essential to reduce myocardial necrosis, preserve ventricular function, and improve survival outcomes. However, delayed presentation remains a significant problem, especially in developing countries, leading to larger infarct sizes and worse clinical outcomes. (Park J, Choi KH, Lee JM, et al. 2019) Ventricular repolarization indices including QT interval ( Measured from the onset of the QRS complex (beginning of Q wave or R if no Q visible)To the end of the T wave returning to the isoelectric line ), QT dispersion (QTD) ( Calculated as: QTD = QT{max} - QT{min}), corrected QT interval (QTc) Calculated using Bazett's formula: QTc = {QT}/{sqrt{RR}. Corrected QT dispersion (cQTD or QTcd) Calculated as: cQTD = QTc{max}- QTc{min}.TPE/QT ratio, Calculated as: {TPE/QT Ratio} = {TPE}/{QT}, T peak-to-Tend interval (TPE) ( Measured from the peak of the T wave To the end of the T wave returning to the isoelectric line ), are non-invasive markers of electrical instability and myocardial injury. Prolongation of these indices has been associated with worse microvascular perfusion (including the no-reflow phenomenon (Abdelmeguid AE, Abdelhamid SM, Abdelhameed KM, et al. 2023) and lower myocardial blush grade [MBG]) (Liu X, Li Y, Li D, et al. 2021) and higher rates of major adverse cardiovascular events (MACE). (Çağdaş M, Rencüzoğulları İ, Karakoyun S, et al. 2018, Abdelmeguid AE, Abdelhamid SM, Abdelhameed KM, et al. 2023, Liu X, Li Y, Li D, et al. 2021) There is limited data assessing the direct relationship between early vs late presentation, repolarization indices measured before and after PCI, and subsequent outcomes in STEMI patients, particularly in our local population.

This study aims to fill this gap by investigating whether timing of presentation significantly affects repolarization indices and whether these indices can predict in-hospital and six-month clinical outcomes.

Inclusion criteria

• Patients presenting with acute STEMI undergoing primary PCI

Exclusion criteria

• 1. Prior myocardial infarction or CABG. 2. Left or right bundle branch block. 3. Atrial fibrillation. 4. Cardiac arrest or cardiogenic shock 5. Valvular heart disease (severe). 6. Use of QT-prolonging medications as anti-arrhythmic, anti-psychotic, anti-depressant and some types of antibiotics.

• Poor quality ECG tracings. 8. Chronic kidney disease stage ≥3. 9. Electrolyte abnormalities at admission 10. Undetermined date of pain