Atrial Fibrillation

AF is the most common sustained arrhythmia encountered in clinical medicine, and it is occurring with increasing frequency in a population that is gradually aging. It is associated with an almost twofold increase in mortality (23) and a fivefold increase in the risk of stroke (24). Most studies have suggested that AF is caused by multiple reentrant wavelets within the atrium. The idea that pacing may prevent AF stems from the observation that patients with symptomatic sinus-node dysfunction had a lower incidence of AF with atrial pacing than with ventricular pacing. A number of possible mechanisms may prevent AF by pacing. In patients with vagally mediated AF (25), pacing appears to be beneficial by preventing the initiating bradycardia. Because AF may be initiated by premature atrial beats (by producing atrial distention and dispersion of atrial refractoriness) atrial pacing may be beneficial by suppressing the extra beats or by altering the atrial activation pattern so that premature beats are unable to initiate reentry (26,27). Lastly, there is evidence of anatomic and electrical changes in the fibrillating atrium (e.g., a marked decrease in the effective refractory period) that favor

Table 1

Prospective Randomized Trials of Comparing Pacing Modes in the Prevention of AF

Table 1

Prospective Randomized Trials of Comparing Pacing Modes in the Prevention of AF

Trial (ref)

# Subjects

Population

Mode

Duration

Results

PASE (15)

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