Reduction in atrial defibrillation threshold by a single linear ablation lesion

Introduction: This study investigated a hybrid approach to reduce the atria l defibrillation threshold (ADFT) by determining the effect of a single lin ear radiofrequency ablation (RFA) lesion on both the ADFT and activation pa tterns during atrial fibrillation (AF), Methods and Results: In 18 open chest sheep (45 to 57 kg), coil defibrillat ion electrodes were placed in a superior vena cava/right ventricular config uration. AF was induced by burst pacing and maintained with acetyl beta -me thylcholine (2 to 42 muL/min). ADFTs were obtained before and after a linea r RFA lesion was created in the left atrium (LAL; n = 6), right atrium (RAL ; n = 6), or neither atrium as a control (n = 6), In animals receiving an L AL, a 504-unipolar-electrode plaque was sutured to the LA. For animals rece iving an RAL, two 504-electrode plaques were placed, one each on the LA and RA, From each plaque, activations were recorded before and after ADFT shoc ks, and organizational characteristics of activations were analyzed using a lgorithms that track individual wavefronts, In sham-treated controls, the A DFT did not change, In contrast, LAL reduced ADFT energy 29%, from 4.5 +/- 2.3 J to 3.2 +/- 2.0 J (P < 0.05), RAL reduced ADFT energy 25%, from 2.0 +/ - 0.9 J to 1.5 +/- 0.7 J (P < 0.05), AF activation was substantially more o rganized after RFA than before RFA for both the RAL- and LAL-treated animal s. Conclusion: A single RFA lesion in either the RA or LA reduces the ADFT in this sheep model, This decrease is associated with an increase in fibrillat ory organization.