Electrode placement significantly affects transthoracic atrial defibrillation thresholds


Background: Placement of external electrodes can significantly affect the success rate of transthoracic atrial defibrillation, but clinical studies have not led to agreement on optimal electrode placements. This study uses an anatomically realistic, finite element model of the human torso for external atrial defibrillation to (1) investigate model parameters of skeletal muscle conductivity and anisotropy and the presence of subcutaneous fat and (2) investigate clinical defibrillation parameters of electrode size, shape, and location. Methods: The model computes electric fields in the atria given electrode location, applied voltage, and tissue conductivities. The model predicts atrial defibrillation threshold (ADFT) energy by requiring a voltage gradient of 5 V/cm over at least 95% of atrial myocardium. Results: The results compare favorably with a clinical study of 301 patients that reported an anterior-posterior (AP) electrode position required approximately 20% less energy than an anterior-anterior (AA) position. Results indicate that a change in electrode size has a different effect for AA compared to AP electrode placements. This study finds that variation in electrode placement by only a few centimeters can change ADFTs by up to 51%. Conclusion: This is the first computer model of transthoracic atrial defibrillation to our knowledge. The sensitivity of defibrillation thresholds to small shifts in electrode placement may account for the disagreement between clinical studies on optimal electrode placements.

Publication Title

Cardiovascular Engineering

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