Effects of beta-blockade with bisoprolol on heart rate variability in advanced heart failure: analysis of scatterplots of R-R intervals at selected heart rates.

The effect of beta-blockade on heart-rate variability was assessed at different heart rates in 52 patients with heart failure included in the randomized, placebo-controlled, Cardiac Insufficiency Bisoprolol Study (CIBIS). Scatterplots of R-R intervals display beat-to-beat variability by plotting each R-R interval against the preceding interval. Scatterplot dispersion at different R-R intervals provides a measure of beat-to-beat heart-rate variability at different heart rates. A 24-hour Holter tape was performed at baseline and after 2 months of treatment with bisoprolol or matched placebo. Geometric measurements of scatterplots were used to determine beat-to-beat dispersion for different R-R intervals. Bisoprolol and placebo groups were well matched at base-line. After 2 months of treatment, bisoprolol significantly increased beat-to-beat variability at the longest R-R intervals (p < 0.05); however, there was no change in scatterplot dispersion at the shortest R-R intervals. This suggests that beta-blockade increases parasympathetic or decreases sympathetic tone or both in heart failure patients only at the slowest heart rates.