Detrended Fluctuation Analysis of Heart and Respiratory Rhythm in Atrial Fibrillation

Atrial fibrillation (AF) is a disorder in which heart rhythm becomes irregular and has an influence on the respiratory rhythm as well as on cardiopulmonary coupling. We applied detrended fluctuation analysis (DFA) method to find correlation properties of heart and respiratory rhythm in order to clarify behavioral pattern of cardiopulmonary coupling in AF. Scaling exponents: alpha(1) (short-range correlations) and alpha(2) (long-range correlations) were calculated on RR intervals and respiratory signal (Resp). Their relationship with heart/respiratory frequency was examined by regression analysis. In comparison to the control group, there was a significant reduction of alpha(1) and alpha(2) of the heart rhythm in AF group, while alpha(2) (Resp) was significantly increased in AF group. In regression analysis, there were significant intrasystemic relationships. In AF, our results imply a compensatory mechanism in regulation of the respiratory rhythm which was not noticed in regulation of the heart rhythm. We can conclude there is a cardiopulmonary coupling in direction heart-respiratory system in AF, but not in the opposite direction because of impaired vagal stimulation of sinoatrial node (SA).