Left atrial size and ablation outcome

TAIPEI, TAIWAN. There is some evidence that a large left atrial diameter (parasternal long-axis view) as determined with transesophageal echocardiography (TEE) is associated with an increased risk of afib recurrence following catheter ablation. Now Dr. Shih-Ann Chen and colleagues at the Taipei Veterans General Hospital report that patients with permanent (persistent or long-standing persistent) atrial fibrillation (AF) have a lower recurrence rate if their pre-procedural left atrial diameter (LAD) is less than 45 mm and their AF terminated spontaneously during their first ablation procedure.

The study involved 87 patients (83% male) who had suffered from permanent AF for an average of 7 years. The patients were divided into two groups depending on their LAD. Group 1 consisted of 49 patients with a LAD below 45 mm (mean of 38 mm) and group 2 consisted of 38 patients with a LAD at or above 45 mm (mean of 49 mm). In group 1, 8% had congestive heart failure as compared to 27% in group 2. Hypertension was about equally common in both groups (35% vs 30%). Thus it is likely, although not stated, that the majority of the groups had lone atrial fibrillation (no underlying heart disease).

All patients underwent circumferential isolation of the pulmonary veins followed by segmental ablation as needed. If this procedure did not terminate the AF, linear ablation was performed at the anterior roof and the lateral mitral isthmus (93% of patients needed this procedure). Finally, if the linear ablation did not result in a return to normal sinus rhythm (NSR), complex-fractionated atrial electrogram mapping was performed and additional ablation done as required (59% of patients needed this step). At the end of the 3 steps, 35% of patients experienced spontaneous termination (39% in group 1 and 29% in group 2); electric cardioversion was used to bring the remaining patients to NSR. The total procedure time in group 1 was 130 minutes vs 162 minutes in group 2 – a remarkably short time for such a complex procedure. All patients were placed on antiarrhythmics for 8 weeks following the procedure.

During follow-up, 73% of patients in group 1 and 74% in group 2 experienced recurrence (an average of 6 months after the initial procedure). A second ablation was performed in 24% of the 87 patients, a third procedure in 6%, and a fourth in one patient (1%). In all cases pulmonary vein reconnections were found and re-ablated. At the end of the 21-month follow-up period, 51% of group 1 were in NSR without the use of antiarrhythmics, while another 39% were afib-free with the use of previously ineffective antiarrhythmics. Corresponding numbers for group 2 were 32% and 36%.

The researchers observed that those participants in group 1 (LAD less than 45 mm) whose AF terminated spontaneously during the initial procedure had a substantially lower risk of recurrence during the follow-up period than did those who had to be cardioverted (15% vs 70%). The corresponding numbers for those in group 2 were 22% and 18% - not a statistically significant difference.

Lo, LW, et al. The impact of left atrial size on long-term outcome of catheter ablation of chronic atrial fibrillation. Journal of Cardiovascular Electrophysiology, Vol. 20, November 2009, pp. 1211-16

Editor’s comment: This study is a good example of just how complex a catheter ablation for permanent AF is and how relatively low the complete success rate (no afib, no drugs) is, especially for patients with an enlarged left atrium. The “take-home” message is – “Don’t wait until your afib becomes permanent or your left atrium enlarged before undergoing ablation or surgery to eliminate afib”.