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Abstract
Atrial fibrillation (AF) is the most common sustained arrhythmia, occurring in approximately 0.4 to 1.0% of the general population. AF can be maintained by rapid focal firing, which may itself be regular but result in fibrillatory activity because of wave breakup in portions of the atrium that fail to follow 1:1 conduction . In addition to their potential role as an AF driver, ectopic foci can contribute to AF by acting on vulnerable reentrant substrates to initiate AF. One form of reentrant AF involves a single, rapidly firing reentrant circuit, which (like rapid focal firing) produces fibrillatory activity by virtue of an irregular, fractionated atrial response.
Conversion of atrial fibrillation and flutter to sinus rhythm results in a transient mechanical dysfunction of atrium and atrial appendage, termed atrial stunning. Atrial stunning has been reported with all modes of conversion of altrial fibrillation and flutter to sinus rhythm including both transthoracic and low energy internal electrical, pharmacological, and spontaneous cardioversion, and conversion by overdrive pacing and by radiofrequency ablation. Atrial stunning is a function of the underlying arrhythmia becoming apparent at the restoration of sinus rhythm, not the function of the mode of conversion, and does not develop after the unsuccessful attempts of cardioversion..