Transmural characteristics of atrial fibrillation in canine models of structural and electrical atrial remodeling assessed by simultaneous epicardial and endocardial mapping

Background

Epicardial mapping has shown that atrial substrate may play a role in the characteristics of the resulting atrial fibrillation (AF). However, it is not known whether these differences also occur in 3 dimensions.

Objective

This study sought to examine the 3-dimensional characteristics of AF by simultaneously analyzing AF on the epicardial and endocardial surfaces.

Methods

Dogs were divided into 5 groups: congestive heart failure (CHF), rapid atrial pacing (RAP), mitral regurgitation (MR), control, and methylcholine. A noncontact mapping catheter (Ensite 3000 [Endocardial Solutions, Inc., St. Paul, Minnesota]) was placed in the left atrium (LA), and electrode plaques (240 unipoles) were placed over the epicardial surface. Several AF episodes of at least 30 s were recorded, and isopotential videos of activation and isochronal maps were constructed. In addition, each pair of matched electrograms were cross-correlated (XC) and analyzed with a fast Fourier transform (FFT).

Results

The RAP model was the only one with an AF mechanism of multiple wavelets in every dog on both surfaces. In addition, when individual signals were compared, the RAP model had the least amount of similarities between the recording surfaces, whereas the CHF model had the most as it had a higher percentage of signals with XC coefficients >0.8 and a higher percentage of signals with similar dominant frequencies (30 ± 35% vs. 12 ± 13% and 66 ± 30% vs. 26 ± 10%, P < .05).

Conclusion

Although the RAP model had similar AF mechanisms in 3 dimensions, this did not correlate to transmural similarities. Focal mechanisms of AF may have a more uniform wavefront of activation, whereas models with mechanisms of multiple wavelets may have more 3-dimensional properties.

Keywords: Mapping, Fourier analysis, Atrial fibrillation, Electrophysiology

Abbreviations: AF, atrial fibrillation, CHF, congestive heart failure, CoV, coefficient of variance, DF, dominant frequency, ECG, electrocardiogram, FFT, fast Fourier transform, LA, left atrium, MR, mitral regurgitation, OI, organization index, RAP, rapid atrial pacing, XC, cross-correlated