Mechanisms of Atrial Fibrillation - Reentry, Rotors and Reality

Abstract

Atrial fibrillation (AF) is the most common sustained arrhythmia encountered in clinical practice, yet our understanding of the mechanisms that initiate and sustain this arrhythmia remains quite poor. Over the last 50 years, various mechanisms of AF have been proposed, yet none has been consistently observed in both experimental studies and in humans. Recently, there has been increasing interest in understanding how spiral waves or rotors - which are specific, organised forms of functional reentry - sustain human AF and how they might be therapeutic targets for catheter-based ablation. The following review describes the historical understanding of reentry and AF mechanisms from earlier in the 20th century, advances in our understanding of mechanisms that are able to sustain AF with a focus on rotors and complex fractionated atrial electrograms (CFAEs), and how the study of AF mechanisms has resulted in new strategies for treating AF with novel forms of catheter ablation.

Keywords: Atrial fibrillation; arrhythmia mechanisms; complex fractionated atrial electrograms; pulmonary vein isolation; reentry; rotor.

Figure 1:. Schematics of Anatomic and Functional Reentrant Circuits

Figure 2:. Leading Circle Reentry

Figure 3:. Experimental Exidence of Leading Circle Reentry

Figure 4:. Schematic of a Rotor

Figure 5:. Initiation of Spiral Reentry in a Continuous, Uniform Sheet Model

Figure 6:. Simultaneously Recorded Electrograms, Pseudoelectrograms and Corresponding Fast Fourier Transformations During an AF Episode

Figure 7:. Left to Right Dominant Frequency Gradients in t he Sheep Left and Right Atria

Figure 8:. Example of a Left Atrial Rotor Visualised with FIRM Mapping