title: Wavelet analysis of cardiac optical mapping data.
abstract: BACKGROUND
  Optical mapping technology is an important tool to study cardiac electrophysiology. Transmembrane fluorescence signals from voltage-dependent dyes need to be preprocessed before analysis to improve the signal-to-noise ratio. Fourier analysis, based on spectral properties of stationary signals, cannot directly provide information on the spectrum changes with respect to time. Fourier filtering has the disadvantage of causing degradation of abrupt waveform changes such as those in action potential signals. Wavelet analysis has the ability to offer simultaneous localization in time and frequency domains, suitable for the analysis and reconstruction of irregular, non-stationary signals like the fast action-potential upstroke, and better than conventional filters for denoising.
  
  
  METHODS
  We applied discrete wavelet transformation for temporal processing of optical mapping signals and wavelet packet analysis approaches to process activation maps from simulated and experimental optical mapping data from canine right atrium. We compared the results obtained with the wavelet approach to a variety of other methods (Fast Fourier Transformation (FFT) with finite or infinite response filtering, and Gaussian filters).
  
  
  RESULTS
  Temporal wavelet analysis improved signal-to-noise ratio (SNR) better than FFT filtering for 5-10dB SNR, and caused less distortion of the action potential waveform over the full range of simulated noise (5-20dB). Spatial wavelet filtering produced more efficient denoising and/or more accurate conduction velocity estimates than Gaussian filtering. Propagation patterns were also best revealed by wavelet filtering.
  
  
  CONCLUSIONS
  Wavelet analysis is a promising tool, facilitating accurate action potential characterization, activation map formation, and conduction velocity estimation.
authors.affiliation: Department of Pharmacology and Therapeutics, McGill University, Montreal, Que., Canada; Research Center, Montreal Heart Institute and Université de Montréal, 5000 Belanger Street East, Montreal, Que., Canada H1T 1C8.
authors.forename: Feng
authors.initials: F
authors.lastname: Xiong
authors.affiliation: Research Center, Montreal Heart Institute and Université de Montréal, 5000 Belanger Street East, Montreal, Que., Canada H1T 1C8.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Qi
authors.affiliation: Department of Pharmacology and Therapeutics, McGill University, Montreal, Que., Canada; Research Center, Montreal Heart Institute and Université de Montréal, 5000 Belanger Street East, Montreal, Que., Canada H1T 1C8; Department of Medicine, Montreal Heart Institute and Université de Montréal, Montreal, Que., Canada.
authors.forename: Stanley
authors.initials: S
authors.lastname: Nattel
authors.affiliation: Research Center, Montreal Heart Institute and Université de Montréal, 5000 Belanger Street East, Montreal, Que., Canada H1T 1C8; Department of Molecular and Integrative Physiology/Institute of Biomedical Engineering, Université de Montréal, Montreal, Que., Canada. Electronic address: philippe.comtois@umontreal.ca.
authors.forename: Philippe
authors.initials: P
authors.lastname: Comtois
mesh_terms: D000200:Action Potentials; D000818:Animals; D004285:Dogs; D004562:Electrocardiography; D006325:Heart Atria / Q000503:physiopathology; D006801:Humans; D008955:Models, Cardiovascular; D012815:Signal Processing, Computer-Assisted; D041622:Tomography, Optical
keywords: Action potential; Bioengineering; Cardiac electrophysiology; Conduction analysis; Filtering methods; Heart arrhythmias; Optical mapping; Signal processing