Abstract 2683: Ischemia, Left Ventricular Depolarization and Sudden Death
Background: Since only a small proportion of acute ischemic events lead to sudden cardiac death (SCD), ECG-based risk stratification could be very useful. Traditional focus has been on the ST-segment (LV repolarization) but findings from a recent animal model of acute ischemia suggest that QRS complex (LV depolarization) should be evaluated as well.
Methods: We performed a pilot study with case-control comparisons from an ongoing community-based investigation of SCD in a metropolitan region in the Pacific Northwest (2002–2009). Cases suffered SCD; cases and controls were matched for presence of significant CAD. All were required to have two 12-lead ECGs for comparison: one non-acute and one during an acute ischemic event. An acute ischemic event was defined as ECG evidence of acute coronary syndrome or acute myocardial infarction (STEMI or Non-STEMI). For cases, acute ischemic events were required to be unrelated to the SCD. QT interval was corrected for heart rate using Bazett’s formula (QTc). Paired t-tests were used to evaluate whether the QRS or QTc intervals differed across acute vs. non-acute ECG pairs in the same individual.
Results: An acute and non-acute pair of ECGs were available for 8 cases and 32 controls. From the overall 40 ECGs, cases had prolonged QRS (mean 99.6 vs 93.1 ms, p=0.09) and QTc (mean 464 vs 432 ms, p=0.07). Comparing the acute and non-acute pair of ECGs in control subjects, there was no difference in QRS duration (p=0.85). For cases, QRS was prolonged in acute ECGs relative to non-acute ECGs (p=0.04). The QTc interval was prolonged in acute vs non-acute ECGs in control subjects (p=0.05), but no difference was observed for case subjects (p=0.92).
Conclusions: Significant QRS prolongation during an acute ischemic event was observed in cases who would suffer SCD but not in controls. This pilot study suggests a continued focus on investigation of ischemia-induced prolonged depolarization as a potential stratifier of SCD risk.