ESSENTIALS OF DIAGNOSIS
Presents as an irregularly irregular heart rhythm on examination and ECG.
Prevention of stroke should be considered in all patients with risk factors for stroke (eg, heart failure, hypertension, age 65 or older, diabetes mellitus, prior history of stroke or TIA, and vascular disease).
Heart rate control with beta-blocker or calcium channel blockers generally required. Restoration of sinus rhythm with cardioversion, antiarrhythmic medications, or catheter ablation in symptomatic patients.
Atrial fibrillation is the most common chronic arrhythmia, with an incidence and prevalence that rise with age, so that it affects approximately 9% of individuals over age 65 years. It occurs in rheumatic and other forms of valvular heart disease, dilated cardiomyopathy, ASD, hypertension, and CHD as well as in patients with no apparent cardiac disease; it may be the initial presenting sign in thyrotoxicosis, and this condition should be excluded with the initial episode. Atrial fibrillation often appears in a paroxysmal fashion before becoming the established rhythm. Pericarditis, chest trauma, thoracic or cardiac surgery, thyroid disorders, obstructive sleep apnea, or pulmonary disease (pneumonia, pulmonary embolism) as well as medications such as theophylline and beta-adrenergic agonists may cause attacks in patients with normal hearts. Acute alcohol excess and alcohol withdrawal—and, in predisposed individuals, even consumption of small amounts of alcohol—may precipitate atrial fibrillation. This latter presentation, which is often termed holiday heart, is usually transient and self-limited. Short-term rate control usually suffices as treatment.
Atrial fibrillation, particularly when the ventricular rate is uncontrolled, can lead to LV dysfunction, heart failure, or myocardial ischemia (when underlying CAD is present). Perhaps the most serious consequence of atrial fibrillation is the propensity for thrombus formation due to stasis in the atria (particularly the left atrial appendage) and consequent embolization, most devastatingly to the cerebral circulation. Untreated, the rate of stroke is approximately 5% per year. However, patients with significant obstructive valvular disease, chronic heart failure or LV dysfunction, diabetes mellitus, hypertension, or age over 75 years and those with a history of prior stroke or other embolic events are at substantially higher risk (up to nearly 20% per year in patients with multiple risk factors) (Table 10–12). A substantial portion of the aging population with hypertension has asymptomatic or “subclinical” atrial fibrillation, which can be detected with monitoring devices and is also associated with increased risk of stroke, particularly if it lasts for 24 hours or longer. It is not clear whether, and for whom, oral anticoagulation should be used for subclinical atrial fibrillation, a question that is being addressed in ongoing clinical trials.
Table 10–12.CHADS2 Risk Score for assessing risk of stroke and for selecting antithrombotic therapy for patients with atrial fibrillation. |Favorite Table|Download (.pdf) Table 10–12. CHADS2 Risk Score for assessing risk of stroke and for selecting antithrombotic therapy for patients with atrial fibrillation.