Methods for Discriminating Pre-Ectopic Sinus Beats

Isolated ectopic beats are usually regarded as a sudden unpredictable event having no correlation with pre-ectopic sinus beats. Actually, non homogenous excitability underlying sinus beats may prepare in short-term the cardiac tissue to originate an ectopic beat. To ascertain whether a triggered activity preludes the ectopic beat, we assessed the statistical differences between ECG waveform of sinus beats preceding a premature ventricular extrasystole beat (pre-ectopic) with respect to non pre-ectopic sinus beats. One hour, high resolution 12-lead ECG recordings were digitally obtained from 10 patients with frequent isolated premature ventricular contraction (PVCs>100/hr). The recordings were processed by the software package MISHA (Mortara Instrument) in order to automatically annotate single beats and to extract for each lead one record per beat with quantitative attribute of ECG waveform. For each recording, 200 isolated premature ventricular beats such that the 3 preceding and 3 following beats were normal sinus beats were randomly sampled; we created, for each of the 200 ectopic beats, a new record having as attributes the maximum, minimum and average value of every original attribute of the 3 preceding sinus beats. Likewise, we randomly sampled 200 sinus beats such that the 3 preceding and following beats were regular as well, and, for each of the 200, created a record in the same fashion. Every time a beat was sampled, the 3 beats preceding it and the 3 beats following it were deleted from the data set, as well as the sampled beat. Thus, every record of the first set represents a pre-ectopic beat, whereas every record of the second set a non pre-ectopic beat. A two-tailed unpaired Student’s T-test and other experiments not only showed that there is a statistically significant difference between the two sets, but also that, for every patient, one attribute of the new data set allows to discriminate between pre-ectopic beats and non pre-ectopic beats in 80% of the cases. Nevertheless, which attribute is the most discriminating varies from patient to patient. Based on these results, we conclude that detectable signs of incoming PVC are present in pre-ectopic sinus beats.