KANSAS CITY, KANSAS. Atrial fibrillation (AF) usually starts out as being intermittent in nature (paroxysmal) with episodes being self-terminating, fairly short, and relatively infrequent. However, as electrical and structural remodeling takes place episodes tend to last longer and become more frequent ("afib begets afib"). Eventually, episodes may become persistent, i.e. lasting more than 7 days and requiring cardioversion to establish normal sinus rhythm (NSR). Finally, the condition may become permanent, i.e. the patient is in afib 24/7 and cannot be brought back to NSR via cardioversion. Sometimes the AF is asymptomatic and is only picked up by chance via a routine electrocardiogram, in which case, it is not unusual to find the patient has likely been in permanent AF for many years. A group of researchers at the University of Kansas Hospitals has just published a study aimed at determining the variables affecting the progression of paroxysmal AF to persistent or permanent.
Their study involved 437 patients who were diagnosed with paroxysmal AF during the period 1999 to 2007 and followed until April 2009. The average age of the patients was 68 years (57% male). Almost 70% had hypertension, 24% had cardiomyopathy (disease of the heart muscle), 15% had suffered a previous stroke, and the average left ventricular ejection fraction was fairly low at 52%. About 75% of the study group were taking beta-blockers, 55% were taking ACE inhibitors or ARBs (angiotensin II receptor blockers), 54% were taking antiarrhythmics, and 55% were on statin drugs. Thus, the study group was in no way characteristic of lone afibbers and no attempt was made to separate out the conclusion between lone afibbers and those afibbers with underlying heart disease. Nevertheless, the findings of the Kansas researchers are of considerable interest.
Of the 437 study participants, 295 (68%) were still experiencing paroxysmal afib after an average follow-up of 8 years. A total of 111 patients (25%) had progressed to persistent afib, and the remaining 33 patients (7%) were in permanent afib after an average follow-up of 5 years. Please note that 11 of the persistent afibbers later progressed to permanent, so the final percentages at the end of follow-up were paroxysmal 68%, persistent 23%, and permanent 9%.
There was no indication that being on antiarrhythmics, beta-blockers, ACE inhibitors, ARBs or statin drugs influence the time to progression. However, an enlarged left atrium and valvular heart disease were strong predictors of progression to permanent AF with an enlarged left atrium increasing risk of progression by a factor of 2.4 and valvular heart disease by a factor of 3. Patients who remained in paroxysmal AF had an average left atrial diameter of 4.1 cm vs. 4.7 cm in those who proceeded to permanent AF. The main risk factors for progression to persistent were an elevated body mass index and cardiomyopathy. Age was not a risk factor for progression to permanent.
The researchers conclude that early treatment of valvular disease and cardiomyopathy may reduce the risk of progression as may weight reduction (if overweight or obese) and catheter ablation while still in the paroxysmal stage.
Pillarisetti, J, et al. Evolution of paroxysmal atrial fibrillation to persistent or permanent atrial fibrillation: predictors of progression. Journal of Atrial Fibrillation , Vol. 1, No. 7, June 2009, pp. 388-94
Editor's comment: It is comforting to have confirmation that the majority of paroxysmal afibbers do not progress to persistent or permanent afib, at least over an 8-year period. I would expect that any progression would be substantially slower among lone afibbers with normal weight and left atrial diameter who, by definition, do not have the two major risk factors for progression – valvular heart disease and cardiomyopathy.