Mutual information analysis of temporal patterns of occurrence of ventricular premature beats

The importance of ventricular premature beats (VPBs) results from their possible association with an increased risk for cardiac sudden death. However, little is known about patterns of VPB generation. The authors applied mutual information (MI) to quantify how VPBs are generated with mutual dependence over time, with larger numbers indicating more mutual relation, and examined its relationship with VPBs/day and Lown grading system. Twenty subjects (Lown grade 3, n=1; 4A, n=9; 4B, n=10) were identified retrospectively as having more than 3,000 of VPB´s during 24-hour Holter monitoring. Ten of these patients had no apparent heart disease (N-group). The other ten had coronary heart disease (C-group). MI had no significant correlation with VPBs/day and showed no significant difference between Lown grades (4A, 2.1±1.4 bits vs. 4B, 2.3±1.4 bits). The authors found that values of MI were variable among N-group (2.2±1.3 bits) and C-group (2.4±1.5 bits). The values of MI of time series of random numbers were all zeros. The authors thought that the mechanism of VPBs in patients with strong generalized dependence of VPBs might be different from that in patients with weak generalized dependence, particularly with random generation of VPBs. The absent relations with, VPBs/day and Lown grades suggested that MI of VPBs could be an independent marker