IOANNINA, GREECE. There is no unanimously accepted definition of lone
atrial fibrillation (LAF). Most experts in the field define it as atrial fibrillation (AF) without underlying structural heart disease. Others define it as AF without heart disease, hypertension or other easily identifiable causes, while still others add the condition that AF patients cannot be classified as having LAF if they are over the age of 60 years. NOTE: In my opinion, including chronological age rather than biological age in a definition of a disease condition makes no sense at all. A recent international consensus statement on nomenclature and classification of AF concludes that LAF is AF in the absence of heart disease, while idiopathic AF is LAF in the absence of any disease that might possibly be a cause such as binge drinking, thyroid disorders, hypoglycemia, electrolyte imbalances, and pheochromocytoma.
A group of Greek researchers recently set out to summarize the current knowledge concerning the characteristics and possible causes of LAF. Following are the highlights of their well-documented findings:
Korantzopoulos, P, et al. 'Lone' atrial fibrillation: hunting for the underlying causes and links. International Journal of Cardiology, Vol. 131, 2009, pp. 180-85 Editor's comment:
- LAF is associated with a low risk of progression to permanent AF, mortality, congestive heart failure, and stroke/transient ischemic attack.
- LAF adversely affects the quality of life and exercise capacity of affected individuals.
- Epidemiological studies have found strong associations between LAF and obesity, sleep apnea, diabetes, metabolic syndrome, alcohol consumption, anger and hostility (in men), pulse pressure, and subclinical atherosclerosis.
- The underlying mechanism of LAF includes increases atrial stretch, imbalance in the autonomic nervous system, systemic inflammation, and oxidative stress.
- LAF is prevalent among relatively young males and most lone afibbers have the paroxysmal (intermittent) variety of the disorder. Episodes are often triggered by sleep, exercise, alcohol use, or eating.
- LAF is especially common among tall, lean and physically fit individuals and in this group the relative significance of triggers may be greater than the atrial substrate. NOTE: This conclusion is based on Patrick Chambers' (PC) evaluation of the data from LAF Survey 11.
- The role of the autonomic nervous system (ANS) in the etiology of LAF is well documented. There is substantial evidence of the existence of an adrenergically (sympathetic) mediated form of LAF triggered by exercise and stress as well as a vagally (parasympathetic) mediated form triggered by rest and sleep.
- The relative hypoglycemia as well as the associated hypokalemia and hypomagnesemia observed during the night may increase the susceptibility to vagally-mediated LAF. NOTE: This conclusion is also based on PC's work.
- Lone afibbers tend to have elevated blood serum levels of B-natriuretic peptide (BNP).
- There is evidence that at least 15% of lone afibbers have a family history of AF. In other words, there is a strong genetic connection in LAF.
- There is some emerging evidence that LAF patients have significantly shorter QT intervals than their age- and gender-matched healthy counterparts and that this may be explained by alterations in the slow component of the delayed rectifier potassium channel (IKs).
- The association between inflammation and LAF is not clear. Some studies conclude that inflammation is a cause of LAF, while others conclude that LAF causes inflammation.
- There is some evidence that an unrecognized inflammation of the heart tissue or lining (myocarditis or pericarditis) may be involved in LAF.
While the majority of the findings in the above report are already well known to regular readers of The AFIB Report
, it is nice to see them confirmed in a prestigious journal like the International Journal of Cardiology
. It is particularly gratifying to see the article written by Patrick Chambers, a once-frequent poster on the Bulletin Board, quoted so extensively. A draft of the article was first published in the February 2006 issue and was discussed extensively in Conference Room Session 55