AUSTIN, TEXAS. The pulmonary veins are the most important sources of "rogue" cells triggering atrial fibrillation (AF) episodes. Thus, they are routinely isolated from the left atrium in all catheter ablations via the aptly named pulmonary vein isolation (PVI) procedure. In the case of paroxysmal (intermittent, self-terminating) AF, a PVI may be enough to establish permanent normal sinus rhythm, while in the case of persistent and long-standing persistent (permanent) AF, other areas extraneous to the pulmonary veins may need to be ablated as well. Now a team of American and Italian electrophysiologists (EPs) reports that the left atrial appendage (LAA) is also an important site involved in the initiation of AF.

Their study involved 987 patients (29% paroxysmal, 71% persistent or permanent) who needed a second (follow-up) procedure. During the procedure the EPs observed firing from the LAA in 266 patients who then underwent further ablation to isolate these trigger points. The majority (58%) of the 266 patients had permanent AF, 24% had persistent AF, and 18% the paroxysmal variety. LAA firing was defined as consistent premature atrial contractions (PACs) with the earliest activation in the LAA (at least 10 PACs per minute), or as AF or atrial tachyarrhythmia (AT) originating from the LAA.

The 266 patients were divided into three groups where group 1 consisted of 43 patients who underwent a redo of the PVI isolation of the superior vena cava and ablation of complex fractionated atrial electrograms as needed, but no specific ablation involving the LAA. Group 2 consisted of 56 patients who underwent the above-mentioned ablations as needed as well as focal ablation of triggers in the LAA. Group 3 consisted of 167 patients who underwent the same ablation protocol as group 1 plus complete isolation of the LAA in a procedure similar to a PVI.

The patients were followed for 12 months, a which time 74% of group 1 had experienced AF recurrence as compared to 68% in group 2 and 15% in group 3. Of the 95 patients who experienced recurrence, 88 underwent a third procedure involving LAA isolation only. This successfully eliminated recurrence in 93% of patients. All patients were discharged on warfarin and remained on anticoagulation for at least 6 months post-procedure. Patients free of AF recurrence underwent transthoracic (TTE) and transesophageal (TEE) echocardiography 3 and 6 months after their procedure to determine if contractility and blood flow through the LAA was sufficient to prevent the formation of blood clots (LAA velocity greater than 0.3 m/sec). At the 6-month follow-up, 54% of patients had satisfactory flow velocity and excellent contractility and warfarin was discontinued in these patients. The meaning 46% of patients were kept on warfarin.

Bi Biase, L, et al. Left atrial appendage: An under-recognized trigger site of atrial fibrillation. Circulation, Vol. 122, July 13, 2010, pp. 109-18

Editor's comment: The observation that the LAA is an important source of AF initiation, particularly in persistent and permanent afibbers, is of significant importance and the finding that AF recurrence can be prevented by electrically isolating the LAA is most encouraging. However, the need for almost half of all patients to continue on warfarin, presumably on a permanent basis, following a LAA isolation may discourage some afibbers from undergoing a LAA isolation procedure.