Importance of heart rate variability in patients with atrial fibrillation

Abstract

The autonomic nervous system plays an important role in the development of atrial fibrillation (AF). One of the most promising markers of autonomic activity is heart rate variability (HRV). Aim: The aim of the study was to evaluate HRV in patients with nonrheumatic atrial fibrillation. Patients and Methods: The study population consisted of 222 patients: group I - 75 pts with previous paroxysmal or persistent non rheumatic AF without antiarrhythmics drugs; group II - 71 pts with non-AF arrhythmias; group III - 76 healthy controls. A 24-hour measurement of HRV was carried out with Holter monitoring. The mean of the following time domain parameters were analyzed: R-R, SDNN (standard deviation of all consecutive sizes (NN) during the total ECG record), SDANN (standard deviation of all consecutive intervals, which are obtained by dividing the entire record in five-minute segments and calculating their means), SDN Ninx (the mean standard deviation of NN intervals in successive 5-minute periods) , pNN50 (the proportion between adjacent NN intervals differing by more than 50 ms the percentage of the estimated total number of NN intervals), and rMSSD (square root of successive NN interval differences). Continuous variables are presented as mean ± standard deviation. Student's t-test, Pearson Chi-square, and Mann-Whitney tests were applied where appropriate. P-value of < 0.05 was considered significant. The HRV prognostic value for AF was evaluated by using ROC curves. Results: According to our data, HRV was significantly lower in the group I compared with the groups II and III (p< 0.05): low HRV (rMSSD <30 ms) had46 patients (pts) (61.3%) in the group I, 21 pts (29.6%) in the group II and2 pts (2.6%) in the group III. Moderate HRV (30 =< rMSSD < 45 ms) had 27 pts (36.0%) in the group I, 25 pts (35.2%) in the group II and 42 pts (55.2%) in the group III. [...].