Atrial fibrillation burden: a 'hard' indicator of therapeutic efficacy and a prognostic marker to boot?

Atrial fibrillation (AF) is associated with embolic accidents and heart failure as well as increased mortality.1 Associated heart disease is known to be an important factor determining mortality.1 On the other hand, the significance of the arrhythmia in patients with lone AF has been more difficult to prove perhaps because of the difficulty of measuring the time spent in AF, the burden of AF, and thus establishing a dose–effect relationship. Somewhat paradoxically, a recent consensus statement2 does not distinguish between the prognostic implications of paroxysmal vs long-standing chronic AF while at the same time recommending anticoagulation before cardioversion of long-lasting AF but not for AF of recent onset. From a mechanistic point of view, the longer the atria remain in fibrillation, the greater the stasis and the likelihood of stasis-generated thrombi. In experimental models, short durations of AF result in less electrical and structural atrial remodelling.3 The duration of atrial stunning following cardioversion may also be proportional to the duration of preceding AF,4 favouring continuing stasis despite the restoration of sinus rhythm. A systemic embolic accident also requires the ejection of left atrial thrombi into the systemic circulation, and reversion to sinus rhythm can provide a sufficiently powerful atrial appendage contraction. One possible reason why the AF burden is … *Corresponding author. Tel: +41 22 3727197, Fax: +41 22 3727229, Email: dipen.shah{at}hcuge.ch