Long-term progression of lone AF
ROCHESTER, MINNESOTA. More than 50 years ago cardiologists at the Mayo Clinic began following a group of lone afibbers in order to determine their long-term prognosis and survival. The group consisted of 34 participants with the paroxysmal variety, 37 with persistent afib, and 5 with permanent afib at entry to the study. Lone AF was defined as atrial fibrillation without underlying structural heart disease or hypertension (no age limitation). Atrial fibrillation was defined as paroxysmal if it terminated on its own, as persistent if cardioversion (electrical or drug-assisted) was required to terminate episodes, and as permanent if sinus rhythm could not be restored or maintained despite intervention. The average age at diagnosis was 44 years and 78% of the group was male. Thirty-four percent of study participants were prescribed digoxin within 30 days of their first episode. The number of "digoxin users" had increased to 75% at the latest follow-up.

After an average follow-up of 30 years, 29% of paroxysmal and persistent afibbers had progressed to permanent AF. It is interesting to note that 68% of persistent afibbers became paroxysmal and 22% became permanent during follow-up. Only 6% of paroxysmal afibbers became persistent, while 41% became permanent. In most cases the progression to permanent AF occurred within the first 15 years after diagnosis.

Survival in the study group at 92% at 15 years and 68% at 30 years was similar to or even slightly better than expected for an age- and sex-matched group of Minnesotans (86% and 57% at 15 and 30 years respectively). Twelve of the reported deaths were due to cardiovascular causes, while the remaining 15 deaths were due to other causes. The development of congestive heart failure (19% of group at 30 years follow-up) was not significantly higher than expected (15%).

During the follow-up, 5 strokes (0.2%/person-year) and 12 transient ischemic attacks (0.5%/person-year) occurred in the group – mostly among permanent afibbers. All strokes and TIAs occurred in participants who had developed one or more risk factors for stroke during follow-up (hypertension in 12 patients, heart failure in 4, and diabetes in 3). Not a single stroke or TIA occurred among lone afibbers with no risk factors for stroke. This prompted the following remark from the researchers:

Our long-term data suggest that the increased risk of stroke in atrial fibrillation is due to "the company it keeps".

In other words, lone atrial fibrillation as such is not a risk factor for ischemic stroke. The overall conclusion of the study is highly reassuring to lone afibbers,

After more than 30 years of follow-up of our rigorously defined cohort, findings confirm that overall survival is not affected adversely by lone atrial fibrillation.

In an accompanying editorial, Dr. Lars Frost of the Aarhus University Hospital in Denmark makes the following interesting comment, "Cardiologists with strong political influence have suggested that a diagnosis of lone atrial fibrillation should be restricted to patients less than 60 years of age, although there is not evidence of any threshold values by age regarding the risk of stroke in patients with atrial fibrillation – or in any other medical condition for that matter."
Jahangir, A, et al. Long-term progression and outcomes with aging in patients with lone atrial fibrillation. Circulation, Vol. 115, June 19, 2007, pp. 3050-56
Frost, L. Lone atrial fibrillation: Good, bad, or ugly? Circulation, Vol. 115, June 19, 2007, pp. 3040-41

Editor's comment: It is indeed encouraging to receive further confirmation that lone AF does not shorten lifespan nor increase stroke risk. It is also a cause for celebration that the conversion from paroxysmal and persistent AF to permanent is less than 1% per person-year. It is likely that it would have been closer to 0% if the majority of study participants had not been prescribed digoxin. This "medicine from hell", for lone afibbers at least, may not only prolong episode duration, but may actually convert paroxysmal AF to permanent.[1,2]
[1] Sticherling, C, et al. Effects of digoxin on acute, atrial fibrillation: Induced changes in atrial refractoriness. Circulation, Vol. 102, November 14, 2000, pp. 2503-08
[2] Falk, RH. Proarrhythmic responses to atrial antiarrhythmic therapy. In Atrial Fibrillation: Mechanisms and Management, edited by Rodney H. Falk and Philip J, Podrid, Lippincott-Raven Publishers, Philadelphia, 2nd edition, 1997, p. 386