title: Application of phase coherence in assessment of spatial alignment of electrodes during simultaneous endocardial-epicardial direct contact mapping of atrial fibrillation.
abstract: OBJECTIVE
  Mapping and interpretation of wave conduction patterns recorded during simultaneous mapping of the electrical activity on both endocardial and epicardial surfaces are challenging because of the difficulty of reconstruction of reciprocal alignment of electrodes in space. Here, we suggest a method to overcome this difficulty using a concept of maximized endo-epicardial phase coherence.
  
  
  RESULTS
  Endo-epicardial mapping was performed in six humans during induced atrial fibrillation (AF) in right atria using two sets of 8 × 8 electrode plaques. For each electrode, mean phase coherence (MPC) with all electrodes on the opposite side of the atrial wall was calculated. Localization error was defined as a distance between the directly opposing electrode and the electrode with the maximal MPC. Overall, there was a linear correlation between MPC and distance between electrodes with R(2) = 0.34. Localization error obtained for electrodes of the plaque in six patients resulted in a mean 2.3 ± 1.9 mm for 25 s electrogram segment length. Eighty-four per cent of the measurements resulted in error smaller than 3.4 mm. The duration of the recording used to compute MPC was negatively correlated with localization error; however, the effect reached plateau for segment durations longer than 15 s.
  
  
  CONCLUSIONS
  Application of the concept of maximized endo-epicardial phase coherence to electrograms during AF allows reconstruction of reciprocal alignment of the electrodes on the opposite side of the atrial wall. This approach may be especially useful in settings where the spatial position of endo- and epicardial electrodes for intracardiac mapping cannot otherwise be determined.
authors.affiliation: Department of Physiology, Maastricht University, 6211 LK Maastricht, The Netherlands University Heart Center, Department of Cardiology and Electrophysiology, University Hospital Hamburg-Eppendorf, 20246 Hamburg, Germany pawel.kuklik@maastrichtuniversity.nl.
authors.forename: Pawel
authors.initials: P
authors.lastname: Kuklik
authors.affiliation: Department of Physiology, Maastricht University, 6211 LK Maastricht, The Netherlands Department of Cardiothoracic Surgery, Maastricht University Medical Centre, 6202 AZ Maastricht, The Netherlands.
authors.forename: Elham
authors.initials: E
authors.lastname: Bidar
authors.affiliation: Department of Physiology, Maastricht University, 6211 LK Maastricht, The Netherlands.
authors.forename: Ali
authors.initials: A
authors.lastname: Gharaviri
authors.affiliation: Department of Cardiothoracic Surgery, Maastricht University Medical Centre, 6202 AZ Maastricht, The Netherlands.
authors.forename: Jos
authors.initials: J
authors.lastname: Maessen
authors.affiliation: Department of Physiology, Maastricht University, 6211 LK Maastricht, The Netherlands.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schotten
mesh_terms: D000200:Action Potentials; D001281:Atrial Fibrillation / Q000175:diagnosis* / Q000503:physiopathology; D003198:Computer Simulation; D004699:Endocardium / Q000503:physiopathology*; D056149:Epicardial Mapping; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008955:Models, Cardiovascular; D010496:Pericardium / Q000503:physiopathology*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors
keywords: Atrial fibrillation; Contact mapping; Electrode localization; Endo–epi dissociation; Hilbert transform; Phase mapping