Frequency domain mapping of atrial fibrillation - methodology, experimental data and clinical implications

Abstract

The concept of dominant frequency (DF) has been used as a way to express local atrial activation rate during atrial fibrillation (AF). The rotor theory explaining the pathophysiology of AF is widely based upon spatial distribution of DF in the atria. Using frequency domain analysis to represent the rate of atrial activation by DF can avoid some of the limitations of time domain analysis of signals during AF. Understanding the concept of DF is of utmost importance to the proper use and interpretation of frequency domain analysis in AF. The current review focuses on the basic principles and methodology of frequency domain analysis using the Fourier transform during different types of AF. It also provides an update of the published experimental and clinical data on frequency domain analysis in light of the rotor theory for AF maintenance.

Fig. (1)

Frequency analysis in case of a regular (A) signal and irregular (B) signal with variable CL and amplitude. The upper panels represent the native signal; middle panels show the changes after rectification. The frequency spectra with the corresponding DF values are shown on the lower panels. The signal in A was recorded during typical atrial flutter with a CL of 280 msec and the signal in B is from an AF episode. Note the narrow DF peak with the harmonics in A and the wider basis of the DF peak along with the numerous smaller peaks in the frequency spectrum in B.

Fig. (2)

Frequency analysis of a signal with slight degree of fragmentation and small CL variation (A) and of a signal with very fragmented electrograms and significant CL variation (B). The native signals in both cases are shown in the upper panels and lower panels demonstrate the frequency spectra of the signals with the corresponding values of DF and RI. Note that in B the frequency spectrum has numerous additional high power peaks apart from the DF peak making accurate interpretation questionable. Both signals were recorded during AF.

Fig. (3)

Frequency analysis demonstrating spatial distribution of DFs derived from signals recorded from the four PV ostia, LA posterior wall, RA/superior vena cava junction and the coronary sinus in a patient with paroxysmal AF. The frequency spectra of the recorded signals are also presented. Note that the highest DF was recorded at the ostium of the left superior PV which was identified as arrhythmogenic in this patient as denoted by the asterisk. Another high DF site was recorded at the ostium of the right inferior PV. Note the lower DF at the coronary sinus and the lowest DF at the RA/superior vena cava junction demonstrating a significant LA-to-RA gradient. The atria are schematically represented as viewed from posterior.