Abstract 932: Temporal Relationship between QTc Prolongation and ST-segment Elevation in Early Transmural Myocardial Ischemia Measured by a Continuous 12-lead ECG Monitor
Introduction: We have previously reported that prolongation in the corrected QT interval (QTc) is the most consistent ECG abnormality seen during early transmural ischemia. However, the time course of QTc compared to ST segment (ST) changes during early transmural ischemia had not been investigated.
Methods: Fourteen consecutive patients undergoing elective percutaneous coronary interventions (PCI) had electrocardiograms (ECGs) continuously recorded using 12-lead Holter Recorder (SeerMCtm ,GE Healthcare). QT intervals and ST segment changes were digitally measured using the Interval Editor (GE Healthcare). The mean QTc and changes in ST segments were plotted over time during the first balloon occlusion. ST changes were measured in the lead with maximum change. QT interval was corrected for the heart rate using the Bazett’s formula.
Results: The average QTc prolonged from 442±16 ms at baseline to 455±18 ms (p=0.01) at a mean of 8 seconds from the balloon occlusion. The maximum ST-elevation was 0.34±0.86 mm and it occurred at mean of 40 sec from balloon inflation. ST elevations were consistently found to occur only after the maximum QTc prolongation (Figure⇓).
Conclusion: By continuous ECG monitoring, QTc prolongation occurs very early during the initial stages of transmural ischemia. The more commonly used marker for transmural ischemia, ST elevation, occurs only after QTc prolongation.