Cardiology Medical News about Atrial Fibrillation

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Dominant Frequency of Atrial Fibrillation Correlates Poorly with Atrial Fibrillation Cycle Length
Circulation: Arrhythmia and Electrophysiology, 10/22/09

Elvan A et al. – DFs from unipolar and bipolar electrograms recorded during AF correlated poorly with mean, median and mode AFCL. If a frequency gradient >25% existed, the site with highest DF corresponded to the site of shortest median AFCL in only 25% of patients. Since spectral analysis is being used to identify ablation sites, these data may have important clinical implications.

Exclusive Author Commentary
Arif Elvan, 10/27/09

Atrial fibrillation (AF) is characterized by beat-to-beat interval changes and different electrogram morphologies. Spectral analysis is increasingly used by electrophysiologists to select target sites for AF ablation. Atrial electrograms are mathematically transformed into a frequency spectrum and the maximum power in this spectrum is defined as the dominant frequency (DF) and used as a measure of atrial excitation rate. High frequency sites are thought to play an important role in the initiation and maintenance of AF, reflecting microreentrant circuits or sites of focal activity that drive AF. Ablation of these high frequency sites can terminate AF. To localise high frequency sites, both spectral analysis and AF cycle length (AFCL) analysis are being used. Activation rate is the key parameter, and therefore cycle length measurements are preferable to determine the dominant frequencies. Determining AFCL requires, however, an interactive technique, to avoid errors and is therefore time consuming. For this reason, spectrum analysis is often the method of choice. However, the spectrum of a signal is not only determined by its cycle length, but morphology and changes in amplitude and intervals play a role as well and will impact DF. The current study shows that the correlation between DFs obtained with spectral analysis and mean, median and mode of AFCL is weak. Importantly, a very weak correlation existed between high frequency sites detected with AFCL measurement and spectral analysis. Since spectral analysis has been clinically used to guide ablation procedures, these data may have important clinical implications. Clinical use of automated systems to target ganglionated plexi or fractionated electrograms will need to keep the limitations of spectral analysis in mind.

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