Esophageal electric fields are correlated to atrial defibrillation thresholds: towards patient-specific optimization of external atrial defibrillation

Esophageal electric fields are predictive of atrial cardioversion success-a finite element analysis

BACKGROUND

Atrial fibrillation (AF) is a debilitating cardiac arrhythmia, one potential treatment of which is external cardioversion. Studies have shown external cardioversion success is affected by electrode placement and that esophageal electric fields (EEFs) during low strength shocks have the potential to be used in determining patient-specific optimal electrode placements during animal experiments. The objective of this study was to determine the relationship between EEFs and atrial defibrillation thresholds (ADFTs) during computer simulations using an anatomically realistic computer model of a human torso.

METHODS

Over 600 electrode placements were simulated during which EEFs were compared to ADFTs.

RESULTS

There was no single optimal electrode placement with multiple electrode placements resulting in similarly low ADFTs. There was over 40% difference in the ADFTs between the most and least optimal electrode configurations. There was no correlation between EEFs and ADFTs for all electrode placements, but a strong negative correlation when small shifts from clinically relevant electrode placements were performed.

CONCLUSIONS

These results suggest a small shifts protocol from clinically relevant electrode placements has the potential to increase the probability of successful cardioversion on the first shock and reduce the cumulative number of shocks and energy to which patients are exposed.

Esophageal electric fields are predictive of atrial defibrillation thresholds

BACKGROUND

Atrial fibrillation (AF) is a common cardiac arrhythmia characterized by disorganized cardiac electrical activity. Defibrillation electrode placement has been shown to affect the amount of energy and number of shocks required to defibrillate. The objective of this study was to investigate the relationship between esophageal electric fields (EEFs) and atrial defibrillation thresholds (ADFTs) to determine the feasibility of using EEFs during a low-strength shock to predict patient-specific defibrillation electrode placements.

METHODS

AF was induced and defibrillated according to a Bayesian four-shock protocol for 12-electrode placements in six pigs. EEFs were measured during each of the four shocks of the protocol and during a 1-J shock for each electrode placement. Squared EEFs (EEF(2) s) during all shocks were compared to the ADFTs using a linear regression.

RESULTS

There was a negative relationship between EEF(2) s during the 1-J shocks and ADFTs, with median R(2) values of 0.863 and 0.840 for anterior-anterior (AA) and anterior-posterior (AP) electrode placements, respectively. There was a strong, positive relationship between applied energy and EEF(2) s, with median R(2) values of at least 0.866 for all animals. The placement with the highest EEF(2) resulted in the lowest ADFT for both AA and AP placements in four of six pigs. In the other two animals, this held for one electrode set but not both.

CONCLUSIONS

There was a strong negative relationship between EEF(2) s during 1-J shocks and ADFTs for both AA and AP electrode placements. These preliminary results suggest that using EEF(2) s to predict patient-specific electrode placements is feasible.