Figure 3:

Distribution of the location, height (topological prominence), and width of QRS-complexes of one patient. To turn a loosely defined heuristic such as “R-wave appears earlier than usual” into an LF, we must characterize the “usual” location of the R-wave. To accomplish this, we we fit a robust Gaussian distribution to model the variance of R-wave locations, and assume any beat located two standard deviations earlier (solid green line at T_{Early R-wave} = 292 ms), than the estimated mean, to be a PVC beat. Since these attributes vary widely from patient-to-patient, we automatically compute these thresholds separately for each patient and heuristic.