BARCELONA, SPAIN. Lone atrial fibrillation (LAF) is defined as AF occurring in the absence of structural heart disease. Idiopathic AF is defined as lone AF of no known cause; ie. thyroid disorders, hemochromatosis, alcoholism, and electrolyte disturbances have been ruled out. Although LAF patients, in most cases idiopathic, constitute between 10 and 30% of all afib patients, comparatively few studies have been done dealing specifically with this condition. A study by researchers at the University of Barcelona is, hopefully, a harbinger of a trend to focus greater efforts on determining the causes and likely progression of LAF.
The study involved 98 patients (71% men with an average age of 48 years) who were admitted to the University hospital's emergency room with AF of no known cause (idiopathic). Most (64.3%) had experienced previous episodes, while the remaining 35.7% showed up with their first episode. Half the patients reverted spontaneously to normal sinus rhythm (NSR) or did so after oral flecainide administration (classified as paroxysmal afibbers), while the other half required electrical cardioversion to convert (classified as persistent afibbers). First-occurrence patients were discharged with no medication, while recurrent patients were discharged on whatever medications they had used prior to the index episode (the episode at which they first were admitted to the ER), or on a class 1C antiarrhythmic (mostly flecainide). Patients for whom class 1C drugs had clearly not worked were recommended to try amiodarone. None of the patients were discharged with a prescription for anticoagulants (warfarin).
During the following 6 months, 57% of the entire patient group experienced at least one subsequent afib episode. Recurrent afib was more common among those with prior episodes before the index episode (65.1%) than among "first-onset" patients (34.9%); this despite the fact that 70% of the "veteran" afibbers were taking antiarrhythmics. As a matter of fact, taking amiodarone or a class 1C antiarrhythmic did not significantly influence the risk of recurrence in this group. The researchers also observed that an enlarged left atrium (dilated anteroposterior LA diameter) was associated with a 30% increased risk of AF recurrence. However, they found no association between recurrence risk and afib type (paroxysmal or persistent).
They conclude that for lone (idiopathic) afibbers who have a recurrent episode and an enlarged left atrium (indexed for body surface area), the probability of another episode is about 90% despite the use of antiarrhythmics. On the other hand, the probability of another episode is only 30% in a patient with normal LA diameter who has just experienced one episode.Arriagada, G, et al. Predictors of arrhythmia recurrence in patients with lone atrial fibrillation. Europace, Vol. 10, 2008, pp. 9-14
Several findings stand out in this excellent report:
- First-onset patients were not put on medication after their first episode. This is in accordance with the 2001 ACC/AHA/ESC recommendations.
- No patients were prescribed warfarin.
- The use of antiarrhythmics was not effective in preventing further episodes in most cases.
Of particular interest is the finding that first-time afibbers with a non-dilated left atrium have only a 30% chance of experiencing another episode in the 6 months following the first one. My guess is that these patients may well be able to hold off subsequent episodes for a long time through trigger avoidance, supplementation, and dietary and lifestyle changes.