he mechanisms of atrial fibrillation (AF) are
complex and associated with structural and
electrical remodeling in the atria and ventricular
myocardium. The key electrophysiological mechanisms
of AF include: 1) focal firing due to triggered
activity (early and delayed afterdepolarizations);
2) multiple re-entries due to shortening of the action
potential; and 3) heterogeneity of impulse conduction
caused by atrial fibrosis. Development and
progression of atrial fibrosis are the hallmark of structural
remodeling in AF and are considered to be the
substrate for AF perpetuation. Advanced atrial
fibrosis is associated with more frequent paroxysms
of AF, transformation of the arrhythmia into a permanent
type, and reduced effectiveness of antiarrhythmic
drug therapy