Ablation success in lone afibbers

MELBOURNE, AUSTRALIA. It looks like our persistent emphasis on distinguishing between vagal, adrenergic and mixed (random) AF has finally penetrated to mainstream medicine. Electrophysiologists at the Royal Melbourne Hospital included the following paragraph in the introduction of their study aimed at determining the relative prevalence of vagal LAF and ablation success among afibbers:

Coumel and coworkers classified paroxysmal AF as either vagal or adrenergic depending on the type of triggers and the temporal distribution of the arrhythmic episodes. Patients with vagal AF were typically young males with episodic AF that characteristically began at night or following the intake of food. The arrhythmic episodes in this original description rarely or never progressed to persistent AF. In contrast, patients with adrenergic AF were older, often with evidence of organic heart disease. Episodes occurred during the day and were associated with exercise or emotional stress.

The Australian study included 209 consecutive patients with paroxysmal lone AF (of an average 10 years duration) referred for pulmonary vein antrum isolation (PVAI or Natale protocol). The average age of the study participants was 57 years and 77% were male. Patients were classified as having vagal afib if 90% or more of their episodes were triggered by a vagal stimulus such as resting or sleeping (96.4%), following a meal (96.4%), late post-exercise (51%), cold stimulus (20%), coughing (7%), and swallowing (2%) with most vagal afibbers having more than one trigger.

Patients in whom 90% or more of episodes were initiated by emotional or physical stress and exercise (AF during or immediately following exercise) were classified as adrenergic, while those who met neither of the above criteria were classified as random. All told, 27% had vagal afib, 7% adrenergic, and the remaining 66% had random afib.

All study participants had a PVAI after which they underwent clinical and electrographic follow-up at 3, 6, 9 and 12 months respectively, and at least every 6 months thereafter. Successful isolation of all pulmonary veins was achieved in 94.3% of the patients. However, 25 patients (12%) needed a second procedure due to recurrence of afib caused by regained conduction between the pulmonary veins and the left atrium. At a mean follow-up of 21 months success rates were as follows:

-
Vagal
Adrenergic
Mixed
Total
Complete success (no afib, no drugs)
47%
69%
52%
57%
Partial success (no afib, but on drugs*)
28%
17%
30%
23%
Failure
25%
14%
18%
20%

* Previously ineffective antiarrhythmics

The differences in complete success rates were not statistically significant.

The Australian researchers conclude that PVAI appears to be similarly effective in patients with vagal, adrenergic, and random paroxysmal AF. They observed no ablatable vagal reflexes during their procedures, but suggest that this may be due to the fact that they were done under general anesthesia, which may have modified the autonomic response. They also noted that afibbers who experienced episodes following their PVAI did not change their trigger classification (from vagal to adrenergic or random, or vice versa).

Rosso, R, et al. Vagal paroxysmal atrial fibrillation: prevalence and ablation outcome in patients without structural heart disease. Journal of Cardiovascular Electrophysiology, December 15, 2009 [Epub ahead of print]

Editor’s comment: This recent Australian study is clearly of great interest to our afib community. It confirms the existence of three different varieties of paroxysmal AF – vagal, adrenergic and random. The percentages found for these three forms are very close to the percentages found in our 2008 Ablation/Maze Survey – for vagal 27% vs. 33%, for adrenergic 7% vs. 7%, and for random 66% vs. 60%. The study also confirms that resting/sleeping, heavy meals, and cold drinks are triggers for vagal afibbers, while emotional and physical stress are triggers for those with adrenergic afib. Of course, there are many more significant triggers than those reported here including caffeine, alcohol, food additive (MSG and aspartame), dehydration, and sleeping on the left side – to name a few. The overall success rate of 57% achieved by the Australian team is approaching the 65% average found for the 15 top-ranked institutions in our 2008 survey and is well above the 32% average for other than top-ranked institutions.