Arrhythmias are a major cause of morbidity in heart failure and rheumatic heart disease and are a contributor to half the mortality from CHD. Many such victims die suddenly, without warning. Together with heart failure, arrhythmias are often the final common pathways of terminal heart disease. Estimates of morbidity and mortality are difficult to obtain. There is good evidence, however, that atrial fibrillation is the most common of the serious arrhythmias and is responsible for substantial morbidity and mortality in the general population.36 Although the true frequency of arrhythmias is not known, in 1997 there were an estimated 3.5 million hospital discharges with arrhythmias as the primary (635,000) or secondary diagnosis, with two-thirds being due to atrial fibrillation.8 Between 1982 and 1995, the rate of hospitalization for atrial fibrillation about doubled.1 In 1995, there were an estimated 3.3 million visits to physicians' offices for arrhythmias, more than due to the cerebrovascular diseases.
The Framingham Study reported estimates for atrial fibrillation. In that population, prevalence rose from 0.5 percent at ages 50 to 59 years to almost 9 percent at ages 80 to 89 years.36 Between 1968 and 1989, age-adjusted prevalence tripled in men but did not change appreciably in women. These trends are unexplained. Incidence also doubles with each successive age decade, to reach almost 5 percent per year at ages 85 to 94 years.
Most cases of atrial fibrillation evolved following development of overt cardiovascular disease. Heart failure, MI, and valvular heart disease were the most powerful precursors, with the relative risks as much as sixfold. Hypertensive cardiovascular disease was the most common prior cardiovascular disease, largely because of its great frequency in the general population. Impaired glucose tolerance was the other major risk factor predisposing substantially to atrial fibrillation.
Atrial fibrillation is associated with increased risks of cardiovascular morbidity and mortality. After adjusting for various factors, there was a three- to fivefold increased risk of stroke, the chief hazard of atrial fibrillation. Atrial fibrillation decreases survival and is associated with a near doubling of the risk of mortality, after adjusting for associated cardiovascular conditions (see Chap. 27).
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