QT Dispersion After Primary Percutaneous Coronary Intervention in Patients With ST-Segment Elevation Myocardial Infarction in Relation to Reperfusion and In-Hospital Complications.

BACKGROUND: Acute myocardial infarction is one of the leading causes of death worldwide, with mortality primarily resulting from complications such as arrhythmia, cardiogenic shock, and heart failure, which are closely related to the success of reperfusion therapy. Among electrocardiogram (ECG) parameters, the QT interval reflects ventricular homogeneity as well as predicts electrical instability. QT dispersion (QTd), the difference between maximum and minimum corrected QT (QTc) intervals, is associated with fatal cardiac arrhythmia. However, the effect of reperfusion therapy on QTd remains controversial. Although successful reperfusion is a major determinant of outcome in ST-segment elevation myocardial infarction (STEMI), adverse complications such as arrhythmia, cardiogenic shock, and heart failure may still occur despite restoration of coronary blood flow. Currently, no specific marker can reliably predict these adverse events. Assessment of QTd may provide additional prognostic information regarding myocardial electrical recovery following primary percutaneous coronary intervention (PPCI).

AIM: This study aimed to evaluate the association between QTd after PPCI and reperfusion status as well as in-hospital complications among patients with STEMI.

METHODS: A total of 108 STEMI patients who underwent PPCI were enrolled. A 12-lead ECG was recorded one hour after PPCI, and QT intervals from 12 leads were manually measured using the slope-intercept method. The QTc interval was calculated using the Fridericia formula. QTd was calculated as the difference between the maximum and minimum QTc intervals.

RESULTS: The mean QTd was 67.68 ± 37.88 milliseconds (ms). QTd was categorized into two groups: >50 ms and ≤50 ms. Reperfusion was measured by ST-segment resolution (STR) and thrombolysis in myocardial infarction (TIMI) flow. In the QTd >50 ms group, 32% had STR ≥70%, while 68% had STR <70%. About 46.6% of the QTd ≤50 ms group had STR ≥70%, whereas 53.4% had STR <70%. This demonstrated that there was no statistically significant association between QTd and STR (p = 0.123). Due to the small sample size and time limitation, only two patients had TIMI 2 flow, whereas the remaining patients had TIMI 3 flow. No statistical significance was observed between QTd and TIMI flow grade (p = 1.000). Cardiogenic shock, heart failure, and reduced ejection fraction (EF) were more frequently observed in the QTd >50 ms group, accounting for 48%, 12%, and 52%, respectively. In the QTd ≤50 ms group, only 5.2% had cardiogenic shock, and 19% had reduced EF but no symptomatic heart failure. There was a significant association between QTd and cardiogenic shock, reduced EF, and symptomatic heart failure with p = 0.001, p = 0.001, and p = 0.008, respectively.

CONCLUSION: There was a significant association between QTd and cardiogenic shock, heart failure, and an EF of less than 50%. Ventricular tachycardia and post-infarction angina occurred in the QTd >50 ms group, despite the lack of statistical significance due to the limited sample size. QTd may reflect electrical instability of the myocardium and could be a non-invasive tool to identify patients at higher risk of adverse in-hospital complications.