Effects of Stepwise Ablation of Chronic Atrial Fibrillation on Atrial Electrical and Mechanical Properties

Abstract

<h4>Objectives</h4>This study sought to evaluate the effects of stepwise catheter ablation of chronic atrial fibrillation (AF) on atrial electrical and mechanical properties.<h4>Background</h4>Although stepwise catheter ablation of chronic AF is associated with acute arrhythmia termination and a favorable clinical outcome, atrial tissue damage following the procedure has not been evaluated.<h4>Methods</h4>Forty patients who had previously undergone catheter ablation of chronic AF were studied. In the index procedure, termination of AF was achieved by catheter ablation alone in 36 of 40 patients (90%). Electroanatomical mapping was performed in sinus rhythm > or =1 month after the index procedure, during which the surface area of scar (bipolar voltage of <0.05 mV), low-voltage tissue (<0.5 mV), and atrial propagation were evaluated. Left atrial (LA) mechanical function was assessed by transthoracic echocardiography.<h4>Results</h4>Electroanatomical mapping showed areas of scar and low-voltage accounting for 31% +/- 12% and 32% +/- 17% of the total LA surface area respectively, with the ablated pulmonary vein region accounting for 20% +/- 4% of the LA surface area. The area of scar outside the pulmonary vein region represented 14% +/- 12% of the LA surface area using the initial randomized ablation strategy, and 6% +/- 8% (p = 0.02) using a specific ablation strategy. Atrial conduction was diversely affected by ablation with a wide range of LA conduction times observed (range 100 to 360 ms). The LA contraction was shown in all patients by the presence of late diastolic mitral flow (37 +/- 15 cm/s) and a mean LA active emptying fraction of 18 +/- 11%. At 9 +/- 5 months of follow-up, 39 patients (98%) were in sinus rhythm.<h4>Conclusions</h4>Stepwise ablation achieving sinus rhythm in patients with chronic AF has a significant impact on LA electrical activity but is associated with recovery of LA function.