From Hurst's: the Heart, 11th ed.
Atrial fibrillation is the most common arrhythmia requiring treatment,
with approximately 2.2 million Americans experiencing paroxysmal or
persistent atrial fibrillation.1,6?9 The overall prevalence in the
general population is estimated to be 0.4 percent.10 The incidence and
prevalence of atrial fibrillation steadily increase with age, such
that this arrhythmia occurs in <0.5 percent of the population below 50
years of age and increases to approximately 2 percent at ages 60 to
69, 4.6 percent for ages 70 to 79, and 8.8 percent for ages 80 to
89.7,11,12 The age-adjusted prevalence of atrial fibrillation is
higher for men than women7,8 and for whites than blacks.9 The
incidence of atrial fibrillation in the Framingham Study was 0.04
percent per year for men aged 30 to 39 and increased to 4.6 percent
per year for men aged 80 to 89.13 The Cardiovascular Health Study7
found a prevalence of atrial fibrillation of 5 percent by 24-h
ambulatory monitoring. Most cases of atrial fibrillation occur in
patients with evidence of structural heart disease, though there may
be no evidence of concomitant disease in over 50 percent of patients
with paroxysmal atrial fibrillation.14?16 In contrast, over 80 percent
of patients with permanent atrial fibrillation have an identifiable
underlying cause.17 The cardiac factors predicting the development of
atrial fibrillation in the Framingham Study were stroke, congestive
heart failure, rheumatic heart disease, and hypertension.9,18 Left
atrial enlargement, increased left ventricular wall thickness, and
reduced left ventricular fractional shortening predict an increased
risk.9,19 The left atrial dimension is a powerful predictor of the
development of nonvalvular atrial fibrillation.20 Electrocardiographic
criteria for left ventricular hypertrophy and a clinical history of
diabetes mellitus have also been associated with an increased risk of
atrial fibrillation.9
Atrial fibrillation confers an increased relative risk of overall
mortality ranging from 1.4 times controls in the Manitoba Study21 to
2.3 times controls in the Whitehall study12 (average 1.7 times
controls)3 and is predominantly due to stroke. The risk of stroke
among patients with nonrheumatic atrial fibrillation is approximately
5 percent per year, with an average relative risk of stroke
approximately 6 times that of age-matched controls.11,12,16,20,22?24
In the absence of anticoagulation, the relative risk of stroke in
patients with rheumatic atrial fibrillation is increased approximately
17-fold.25 The Framingham Study demonstrated that the risk of stroke
in atrial fibrillation is clearly related to age, with an annual risk
of stroke of 1.5 percent in patients aged 50 to 59 years, which
increased to 23.5 percent in patients aged 80 to 89 years.11 The risk
of stroke in nonvalvular atrial fibrillation has been estimated to be
approximately 7 percent per year.3,26?29 The development of atrial
fibrillation is a strong predictor of increased mortality in cardiac
conditions such as hypertrophic or restrictive cardiomyopathy.30?33 |
