FLORENCE, ITALY. Paroxysmal (intermittent, self-terminating) atrial fibrillation may over time progress to persistent or permanent afib (episodes lasting 7 days or longer). It is not clear why some paroxysmal afibbers progress to the persistent variety, while other remain paroxysmal for decades. A group of American and Italian researchers now provide at least a partial answer to this question.

Their study involved 330 patients with a history of paroxysmal AF (mean age of 70 years, 61% male) who had had a pacemaker implanted to deal with bradycardia (slow heart beat). Most study participants had underlying heart disease, but 21% were lone afibbers. The pacemaker (Medtronic AT501) automatically recorded the daily burden (duration) of afib and tachycardia for an average of 400 days. After a mean interval of 147 days, 24% of the patients progressed to persistent afib. The researchers made the following interesting observations.

• The prevalence of lone atrial fibrillation (LAF) did not differ between the group that remained in paroxysmal afib and the one that progressed to persistent afib.
• Patients with congestive heart failure were significantly more likely to progress to persistent AF.
• Patients destined to progress to persistent AF experienced a higher daily afib burden and a higher probability of experiencing afib on any given day than those in the paroxysmal group.
• The mean daily afib burden in the group destined for progression to persistent AF increased by about 14 seconds/day, while it stayed relatively constant in the group that remained paroxysmal.
• Lone afibbers experienced significantly more PACs (premature atrial beats, ectopics) than did patients with CVD. However, the incidence of these ectopics decreased over time.
• The conversion to persistent afib occurred suddenly and was often preceded by a period of normal sinus rhythm.
• It is possible that treatment with ACE inhibitors or angiotensin receptor blockers (ARBs) may slow down the remodeling that underlies progression to persistent AF.

The researchers conclude that, "Our results suggest that functional electrical remodeling may not impact all patients or inevitably lead to increasing AT/AF burden and persistent AF. In fact, a large proportion of patients may not increase their AT/AF burden, particularly in the absence of CVD." Saksena, S, et al. Progression of paroxysmal atrial fibrillation to persistent atrial fibrillation in patients with bradyarrhythmias. American Heart Journal, Vol. 154, November 2007, pp. 884-92

Editor's comment: This study indicates that a steady progression of afib burden (longer and more frequent episodes) may lead to persistent afib. Thus, if such a trend is noted, it may be worth trying an ACE inhibitor or an ARB.