Dynamics of wavelets and their role in atrial fibrillation in the isolated sheep heart.
BACKGROUND
The multiple wavelet hypothesis is the most commonly accepted mechanism underlying atrial fibrillation (AF). However, high frequency periodic activity has recently been suggested to underlie atrial fibrillation in the isolated sheep heart. We hypothesized that in this model, multiple wavelets during AF are generated by fibrillatory conduction away from periodic sources and by themselves may not be essential for AF maintenance.


RESULTS
We have used a new method of phase mapping that enables identification of phase singularities (PSs), which flank individual wavelets during sustained AF. The approach enabled characterization of the initiation, termination, and lifespan of wavelets formed as a result of wavebreaks, which are created by the interaction of wave fronts with functional and anatomical obstacles in their path. AF was induced in six Langendorff-perfused sheep hearts in the presence of acetylcholine. High resolution video imaging was utilized in the presence of a voltage sensitive dye; two-dimensional phase maps were constructed from optical recordings. The major results were as follows: (1) the critical inter-PS/wavelet distance for the formation of rotors was 4 mm, (2) the spatial distribution of wavelets/PSs was non-random. (3) the lifespan of PSs/wavelets was short; 98% of PSs/wavelets existed for < 1 rotation, and (4) the mean number of waves that entered our mapping field (15.7 +/- 1.6) exceeded the mean number of waves that exited it (9.7 +/- 1.5; P < 0.001).


CONCLUSIONS
Our results strongly suggest that multiple wavelets may result from breakup of high frequency organized waves in the isolated Langendorff-perfused sheep heart, and as such are not a robust mechanism for the maintenance of AF in our model.
Chen
J
J
Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY, USA.
Mandapati
R
R
Berenfeld
O
O
Skanes
A C
AC
Gray
R A
RA
Jalife
J
J
D000109:Acetylcholine; D000704:Analysis of Variance; D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology*; D016275:Atrial Function / Q000502:physiology*; D016009:Chi-Square Distribution; D003627:Data Interpretation, Statistical; D004195:Disease Models, Animal; D005260:Female; D005456:Fluorescent Dyes; D008297:Male; D010477:Perfusion; D012756:Sheep; D014741:Video Recording
D005456:Fluorescent Dyes; D000109:Acetylcholine