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Figure 4 Shock Frequency by Center and Era

The 2 California centers were combined and analyzed as 1 center because they merged electrophysiology programs with overlapping implanting physicians, and also to allow adequate sample size. Appropriate shock frequency by center (top panel) and by era of initial device implantation (middle panel). Overall, secondary indications patients are more likely to have received an appropriate shock than those implanted for primary indications (32% vs. 17%, p < 0.001); however, there were no significant differences between centers. Appropriate shocks were more common in patients implanted in the earlier era (p < 0.05), regardless of indication type. Inappropriate shock frequency by center and overall (bottom panel). The proportion of inappropriate shocks does not differ for primary and secondary indications, and there is no significant difference (p > 0.05) between centers. Center A had a trend toward less inappropriate shocks in secondary indications, but this was also not statistically significant.