Increased Sample Entropy and High Heart Rate Variability Fluctuation in Persistent Atrial Fibrillation as Compared with Paroxysmal Atrial Fibrillation: A Matched Case-Control Study

The relationship between atrial fibrillation (AF) and distortion of autonomic function is reported in the literature. We aim to evaluate sample entropy (SampEn) and heart rate variability (HRV) in patients with persistent AF and compare them with patients suffering from paroxysmal AF. SampEn and HRV during the presentation of AF were analyzed. In patients with persistent AF, there were significant increases in SampEn and increases in the proportion of normal-to-normal (NN) intervals more than 50 ms, NN intervals higher than 50 ms (pNN50), and a decrease in low-frequency power (LF) compared to patients with paroxysmal AF. The major HRV parameters (increased pNN50 and decreased LF) along with nonlinear data (increased standard deviation of the distances the dots lie from the boundary of identity and decreased detrended fluctuation analysis coefficient) provide pieces of evidence based on a neural mechanism underlying AF. The higher SampEn values correlate to the high fluctuation of HRV in persistent AF patients compared to those with paroxysmal AF. In conclusion, increased SampEn and high fluctuation of HRV may induce AF to become persistent.