Correlation between time-domain measures of heart rate variability and scatterplots in patients with healed myocardial infarcts and the influence of metoprolol.

Scatterplots (displays of each RR interval as a function of the preceding RR interval) provide a visual assessment of nonrandom variations in heart rate. In a recent study, scatterplot length, width, and area correlated with time-domain measures of heart rate variability (HRV) in survivors of recent myocardial infarction (MI) receiving a beta blocker. We performed this study to (1) assess the relation between time-domain measures of HRV and scatterplot indexes in survivors of remote MI not receiving metoprolol and (2) to determine if metoprolol influenced scatterplot indexes. In 28 survivors of remote MI, HRV time-domain variables and scatterplot indexes were measured after 2 weeks off and 2 weeks on metoprolol. Off metoprolol, scatterplot length correlated with long-term HRV variables (SD of the difference of all RR intervals [r = 0.98], SD of the average of all 5-minute intervals [r = 0.97]), and scatterplot width correlated with short-term HRV variables (root-mean-square successive differences between RR intrevals [rMSSD] [r = 0.88]). Metoprolol increased time-domain HRV variables (mean RR interval, rMSSD, and proportion of adjacent RR intervals differing by > 50 ms [pNN50 (%)]) but did not alter scatterplot indexes. Thus, scatterplot indexes correlate with time-domain measures of HRV in survivors of remote MI not receiving metoprolol. In contrast to HRV time-domain variables, scatterplot indexes are not influenced by metoprolol.