Abstract 2855: Roles of the Left Atrial Roof and Pulmonary Veins in the Anatomic Substrate for Atrial Fibrillation and Atrial Fibrillation Ablation
Background: Linear left atrial roof ablation (LARA) after pulmonary vein (PV) encircling ablation (PVEA) improves success rates of persistent-AF ablation. However, the individual contribution of each component is poorly understood, so we tested randomized application of each in a canine AF model.
Methods: An AF substrate was created by atrial tachypacing (400 bpm, 5 weeks) in 13 dogs. In 7, PVEA preceded LARA; in 6, the order was reversed. EP measurements and 240 epicardial electrode AF activation maps were obtained before and after each ablation step. Vulnerability to AF induction by single S2s (AFV) and mean duration of burst pacing-induced AF (AFD) were determined as vulnerability and persistence indices respectively.
Results: PVEA decreased AFV from 91±4 to 59±5% (p<0.001), but did not terminate persistent AF or affect AFD (1036±208 s pre vs 953±206 s post PVEA). LARA terminated AF in 6/9 dogs (67%, P<0.01 vs PVEA) and reduced AFD (934±232 to 322±183 s, p<0.05) without affecting AFV (73±9 vs 71±10%). S2 sites with successful AF induction had shorter ERPs (74±5 ms vs 98±6 ms at negative sites, p<0.05) at baseline. Neither PVEA nor LARA affected overall atrial ERP; however, suppression of AF induction by PVEA correlated with larger regional ERP prolongation (81±2 to 106±6 ms, p<0.05) at sites with suppressed AF induction vs. those without (74±6 to 78±9 ms, p=NS). Mapping of reexcitation sites during AF showed LA-dominant complex reentries at baseline (LA 9.4±0.9 vs RA 1.1±0.3 reexcitations/0.5 s mapping window, p<0.001), which frequently included the LA roof (44±9% of LA reexcitations). LARA terminated AF by interrupting rapid LA-roof reentry circuits. In 2/6 cases, peri-mitral macroreentry caused regular atrial tachycardia after elimination of persistent AF by LARA. After PVEA, AF was frequently maintained by stable reentry around the PVEA line.
Conclusions: Both PVEA and LARA had beneficial but limited and specific actions in this dog model. LARA suppressed AF perpetuation by interrupting LA reentry circuits. PVEA suppressed AF initiation by prolonging regional ERP but failed to affect the AF-perpetuating substrate. These findings indicate the need to systematically study individual step-wise components to refine ablation procedures for persistent AF.