Atrial fibrillation （AF）, the most common cardiac arrhythmia that requires treatment, has been the subject of increased interest and intensive clinical research in recent years. Management strategies are heavily influenced by the temporal
pattern
of
the arrhythmia （paroxysmal or chronic） and by the clinical setting. The clinical presentations and associations of AF are very broad, with symptoms that range from unrecognizable to severely disabling. The hemodynamic consequences of AF are due
to 1）
the loss of atrial systole and 2） a rapid ventricular rate that decreases the diastolic filling period of the left ventricle and the diastolic flow time of the coronary arteries. There is a tendency toward a more aggressive approach to early
reversion,
because of 1） the demonstrated effects of 'electrical remodeling' of atrial myocytes during AF, which favor persistence of the arrhythmia and resistance to reversion and 2） the increased thromboembolic risk of patients with AF lasting 48 hours
or
more. If cardioversion is to be attempted in these patients, 3 weeks of anticoagulation should precede the procedure to reduce embolic risk. An attempt to revert to sinus rhythm either pharmacologically or electrically, the latter usually with a
concomitant pharmacological agent, may be an appropriate option. Long-term anticoagulant with warfarin is indicated for patients with AF lasting more than 48 hours. The decision to intervene in longer episodes of AF is based on the balance
between
hemodynamic tolerance and the likelihood of being able to control future episodes.
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