Dependence of premature ventricular complexes on heart rate ---it's not that simple

Introduction Frequent premature ventricular complexes (PVCs) can lead to adverse health conditions such as cardiomyopathy. The linear correlation between PVC frequency and heart rate (as positive, negative, or neutral) has been proposed as a measure to guide treatment with beta-blockers. We evaluate the robustness of this measure to day-to-day variability and measurement methodology. Methods We analyzed 82 multi-day ECG recordings collected from 48 patients with frequent PVCs (burden 1-44%). For each record, the linear correlation between PVC frequency and heart rate was computed for different 24-hour periods and using different time interval lengths to determine the PVC frequency and average heart rate. Results Using a 1-hour time interval, the correlation between PVC frequency and heart rate was consistently positive, negative or neutral on different days in 19.5% of patients. Using shorter time intervals, the correlation was consistent in 34.1-58.5% of patients. Using 1-minute time intervals emphasized a nonlinear dependence of PVC frequency on heart rate in most patients. Conclusion In patients with frequent PVCs, linear correlation of PVC frequency with heart rate is variable across different 24-hour periods and different interval lengths used to compute the average heart rate. The variable and often nonlinear dependence of PVC frequency on heart rate suggests that classification based on linear correlation should be used with caution.