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.