Atrial fibrillation (AF) and atrial flutter are common arrhythmias associated with a variety of cardiac conditions. AF, the most common sustained cardiac arrhythmia encountered in clinical practice, is increasing in prevalence.1,2,3 These arrhythmias may be associated with deterioration of hemodynamics, a wide spectrum of symptoms, and significant morbidity or mortality. Perhaps because no single therapy has been shown to be ideal for all patients, there are a variety of treatment strategies that may be applied to these arrhythmias. These include no therapy at all, anticoagulation, rhythm control, and rate control.2,3 This chapter describes the epidemiology, electrophysiologic mechanisms, and approach to management of patients with AF and atrial flutter.
AF is characterized by temporally and spatially varying rapid disorganized atrial electrical activation and uncoordinated atrial contraction. The surface electrocardiogram (ECG) characteristically demonstrates rapid atrial fibrillatory waves with changing morphology and rate, and a ventricular response that is usually irregularly irregular (Fig. 83–1).
Twelve-lead electrocardiogram of atrial fibrillation. Note the rapid, irregular, low-amplitude fibrillatory waves with varying morphology and an irregularly irregular ventricular response.
AF has been classified into four categories: paroxysmal, persistent, longstanding persistent, and permanent.3 Paroxysmal AF is characterized by self-terminating episodes that generally last < 7 days (most < 24 hours),="" whereas="" persistent="" af="" generally="" lasts=""> 7 days and often requires electrical or pharmacologic cardioversion. Longstanding AF has been continuous for at least a year. It is recognized that many patients have both paroxysmal and persistent episodes of AF, and in general, we characterize such a patient by their more typical form of AF. AF is classified as permanent when it has failed cardioversion or when further attempts to terminate the arrhythmia are deemed futile. At the initial detection of AF, it may be difficult to be certain of the subsequent pattern of duration and frequency of recurrences. Thus, a designation of first detected episode of AF is made on the initial diagnosis. When the patient has experienced two or more episodes, AF is classified as recurrent. The term lone AF refers to AF occurring in the absence of cardiac disease or other known etiologic factors, usually in relatively young individuals.3 Most cases of AF occur in patients with evidence of structural heart disease, but there may be no evidence of concomitant disease in others, especially with paroxysmal AF.3 By contrast, > 80% of patients with permanent AF have an identifiable underlying cause.4 The definition of chronic AF varies greatly in the literature, and the terminology is best avoided.
It is estimated that 2.2 to 5.0 million Americans and 4.5 million Europeans experience AF.1,2,3,5 The incidence and prevalence of AF steadily increase with age, such that this arrhythmia ...