Risk factors for lone atrial fibrillation

UTRECHT, THE NETHERLANDS. The majority (80-90%) of all patients with atrial fibrillation (AF) have some type of cardiovascular disease or abnormality that can explain the cause of their AF. Thus heart disease-related AF involves an arrhythmogenic substrate, that is, an atria which is diseased, has been stretched, or contains a substantial amount of fibrotic tissue likely formed by long-term inflammation.

On the other hand, lone atrial fibrillation, does not involve diseased or otherwise compromised atria, but is rather an “electrical” problem where certain triggers initiate afib episodes through their action on especially sensitive foci mostly located in and around the entrances of the pulmonary veins into the left atrium. This explains why lone afibbers have normal life expectancy, a low stroke risk, and why paroxysmal (intermittent) afib rarely progresses to persistent or permanent. However, for AF patients with diseased atria (arrhythmogenic substrate) the situation is quite different. These patients have a substantially greater stroke risk, higher mortality, and are much more likely to progress from paroxysmal to permanent AF.

While heart disease is, by definition, not a cause of lone AF, there are other known causes. First among these are electrolyte disturbances (particularly deficiencies in magnesium and potassium) and autonomic nervous system imbalances. However, alcohol consumption, especially binge drinking, and cocaine and certain pharmaceutical drugs can also increase the risk of lone afib. Thyroid disorders can be an underlying cause, as can hypoglycemia and an excessive consumption of tyramine-containing foods. It is also clear that chromosomal abnormalities can increase the risk of lone afib. A recent LAF survey revealed that 43% of 100 respondents had a close relative with cardiac arrhythmia – so the “genetic connection” is by no means uncommon. Finally, there is also evidence that the rare disease pheochromocytoma can cause AF to develop. Once all these possible causes have been ruled out, lone atrial fibrillation becomes “idiopathic” which really is the proper designation for the type of afib most “members” of www.afibbers.org experience.

Lately, several additional initiators of lone AF have been discovered. In a recent review by Dutch researchers it is pointed out that obesity, obstructive sleep apnea (OSA), increased pulse pressure (the difference between systolic [pumping] and diastolic [filling] blood pressure), systemic inflammation, and long-term participation in vigorous endurance sports have all been associated with an increased risk of developing AF.

Obese people (BMI greater than 30) have been found to have twice the risk of developing lone afib when compared to those with normal body weight (BMI between 18.5 and 25 kg/sq.m). Similarly, the presence of OSA increases afib risk by a factor of 2. Several studies have found a clear association between systemic inflammation (high levels of hs C-reactive protein and interleukins) and the presence of lone AF, but it is not clear whether inflammation causes afib or afib results in inflammation.

Schoonderwoerd, BA, et al. New risk factors for atrial fibrillation: causes of ‘not-so-lone atrial fibrillation’. Europace, Vol. 10, 2008, pp. 668-73

Editor’s comment: Although it is of great interest to discover additional possible causes of afib, the great majority of lone afibbers do not have any of these conditions, so the most important causes of the lone afib epidemic are still to be discovered.