Effects of Beta Blocker Therapy on RR Interval Correlations During Exercise.

The effects of beta blockers (BBs) on heart rate (HR) and HR variability (HRV) are well known in general, but RR interval (RRI) correlations during an exercise test have not been previously studied in detail. We analyzed RRIs extracted from Mason-Likar modified 12-lead ECG recordings during a clinical exercise test ( $N\ =\ 2257$ , of which 1227 with BBs) from the FINCAVAS database. We computed the short-term scaling exponent $\alpha_{1}$ of detrended fluctuation analysis (DFA) in one-minute segments before, during and after exercise. Several confounding factors such as age, sex, diseases and medication were taken into account with propensity score matching. During rest, BBs significantly reduced the DFA scaling exponents, but the effect was opposite in the recovery phase. Thus, BBs were found to limit the $\alpha_{1}$ range. However, propensity score matching accounting for the confounding factors was found to diminish the differences. The dependency of the scaling exponents on the HR was found to be similar in both groups, and disappeared during the exercise.