Abstract 2398: The Role of RR-Interval Variability Preceding Ventricular Fibrillation in ST Elevation Acute Myocardial Infarction
Introduction: Ischemic ventricular fibrillation (iVF) complicating ST elevation myocardial infarction (STEMI) is a leading cause of sudden cardiac death. The hypothesis was tested that first STEMI patients (pts) developing iVF show more RR-interval variability (RRV) than first STEMI pts without iVF.
Methods: Continuous digital 12-lead Holter recordings (DR180+, NorthEast Monitoring, Maynard, MA, USA) from 3 separate first STEMI studies, characterized by pts with chest pain <6 hours and reperfusion therapy consisting of thrombolytics (n=444) or primary PCI (n=1038), were examined for the occurrence of iVF. 41 pts developing iVF before onset of reperfusion were studied and compared with 123 randomly selected pts without iVF, matched for study population. The computerized labelling of QRS complexes in the ECG recordings was reviewed on a beat-to-beat basis by a trained physician. Using designated software, time intervals from start of Holter to onset of iVF and equivalent time intervals in the controls were used for calculations. Standard heart rate variability (HRV) was measured as the ‘root mean square of the difference of successive RR-intervals’ (RMSSD). RRV was calculated as RMSSD using all complexes, including those of ventricular origin, contrary to the standard HRV measure.
Results: No differences were present between the study and control group regarding baseline and enzymatic data, except for a higher percentage of males among the iVF pts (90% vs. 72%; p = 0.03). Mean age was 60 ± 12 years, 77% were male and 29 % had anterior wall infarctions. Compared to controls, iVF patients showed a higher median RRV (132 [IQR 100–197] ms vs. 67 [IQR 39–108] ms; p < 0.001), a higher median HRV (70 [IQR 37–101] ms vs. 42 [IQR 25– 60] ms; p = 0.005) and a higher median number of ventricular premature complexes (73 [IQR 19–268] vs. 16 [IQR 2–106]; p = 0.006). Multivariate analysis revealed RRV to be the only independent predictor of the occurrence of iVF (OR 1.018, 95%-CI 1.010–1.025; p < 0.001).
Conclusion: In the period before iVF, RRV measured by RMSSD is higher in STEMI pts with iVF, independent of HRV and the number of ventricular premature complexes. This finding could have important pathophysiological and clinical implications.