Abstract
BackgroundThe dominant frequency of the Fourier power spectrum is useful to analyze complex fractionated atrial electrograms (CFAE), but spectral resolution is limited and uniform from DC to the Nyquist frequency. Herein the spectral resolution of a recently described and relatively new spectral estimation technique is compared to the Fourier radix-2 implementation.MethodsIn 10 paroxysmal and 10 persistent atrial fibrillation patients, 216 CFAE were acquired from the pulmonary vein ostia and left atrial free wall (977 Hz sampling rate, 8192 sample points, 8.4 s duration). With these parameter values, in the physiologic range of 3–10 Hz, two frequency components can theoretically be resolved at 0.24 Hz using Fourier analysis and at 0.10 Hz on average using the new technique. For testing, two closely-spaced periodic components were synthesized from two different CFAE recordings, and combined with two other CFAE recordings magnified 2×, that served as interference signals. The ability to resolve synthesized frequency components in the range 3–4 Hz, 4–5 Hz, …, 9–10 Hz was determined for 15 trials each (105 total).ResultsWith the added interference, frequency resolution averaged 0.29 ± 0.22 Hz for Fourier versus 0.16 ± 0.10 Hz for the new method (p < 0.001). The misalignment error of spectral peaks versus actual values was ±0.023 Hz for Fourier and ±0.009 Hz for the new method (p < 0.001). One or both synthesized peaks were lost in the noise floor 13/105 times using Fourier versus 4/105 times using the new method.ConclusionsWithin the physiologically relevant frequency range for characterization of CFAE, the new method has approximately twice the spectral resolution of Fourier analysis, there is less error in estimating frequencies, and peaks appear more readily above the noise floor. Theoretically, when interference is not present, to resolve frequency components separated by 0.10 Hz using Fourier analysis would require an 18.2 s sequence duration, versus 8.4 s with the new method.
Highlights
Accurate spectral resolution is important for analysis of atrial fibrillation (AF) in the frequency domain [1]
In recent work we introduced a paradigm for spectral estimation and signal transformation of complex fractionated atrial electrograms (CFAE) based upon ensemble averaging [7,8,9]
In this study we demonstrated that the resolving power to discern two closely-spaced synthesized frequency components was significantly greater using a new spectral estimation technique as compared with Fourier analysis
Summary
Accurate spectral resolution is important for analysis of atrial fibrillation (AF) in the frequency domain [1]. Since frequency shifts can be minute, sufficient resolving power is essential to detect these differences over short time intervals. This becomes more difficult when signal-to-noise ratio is low, as is often the case. One way to improve continuity in the frequency domain representation of AF from one instance of time to the is to model and update the spectral profile based on new signal information as it is acquired in atrial fibrillation signals [2,3]. When resolving power is insufficient, a broad spectral peak in the Fourier power spectrum may be indicative of either a temporal variation in the frequency of a single component, or the merging of multi-component independent sources [5]. The spectral resolution of a recently described and relatively new spectral estimation technique is compared to the Fourier radix-2 implementation
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