Systematic evaluation of time-frequency parameters from surface electrocardiograms for monitoring amiodarone effects in atrial fibrillation

Determination of spectral parameters from surface electrocardiograms (ECG) during atrial fibrillation (AF) may prove useful for understanding underlying pathomechanisms and selecting optimal treatment. Dominant fibrillatory frequency is the most commonly used parameter today, but bandwidth (BW) and an index of temporal frequency stability (IS) have also been described. However, no study has systematically evaluated the influence of parameter settings on interindividual differences and distinguishing antiarrhythmic drug effects. This study included 20 patients with persistent AF. ECG recordings were taken before and after amiodarone administration. The atrial fibrillatory component was extracted from ECG by Principal Component Analysis techniques, and the spectral properties were obtained from the Welch's periodogram and the time-frequency transform. The following parameters were evaluated: BW, instantaneous main frequency and IS. Several parameter settings were studied in order to determine the values that maximize interindividual differences and allow monitoring of drug effects. Baseline frequency measured 6.54 +/- 0.53Hz (range 5.7 to 7.4Hz) and was reduced to 5.64 +/- 0.54 Hz (range 4.8 to 6.5Hz) by amiodarone (p < 0.0001). Using Receiver Operating Characteristic analysis with a temporal resolution of Is in the time-frequency distribution, BW obtained from a threshold at 50% of main peak amplitude and IS based on consecutive frequency differences between 0.5 and 0.9Hz resulted in both maximal interindividual parameter differences and differentiation of baseline and amiodarone recordings.