Chapter 40

Atrial fibrillation, atrial flutter, and atrial tachycardia are common arrhythmias associated with a variety of cardiac conditions. Atrial fibrillation, the most common sustained cardiac arrhythmia encountered in clinical practice, is increasing in prevalence.1-3 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.3 This chapter describes the epidemiology, electrophysiologic mechanisms, and approach to management of patients with atrial fibrillation, atrial flutter, and atrial tachycardia.

Atrial fibrillation (AF) is characterized by temporally and spatially varying rapid disorganized atrial electrical activation and uncoordinated atrial contraction. The surface electrocardiogram characteristically demonstrates rapid atrial fibrillatory waves with changing morphology and rate and a ventricular response that is usually irregularly irregular (Fig. 40–1)

###### Figure 40–1

Twelve-lead electrocardiogram of atrial fibrillation. Note the rapid, irregular, low-amplitude fibrillatory waves with varying morphology and an irregularly irregular ventricular response.

### Classification

The American Heart Association (AHA), American College of Cardiology (ACC), and the European Society of Cardiology (ESC) have proposed a standardized classification of AF into three categories: paroxysmal, 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. 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 ≥2 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 (generally <60 years of age).3 Most cases of AF occur in patients with evidence of structural heart disease, but there may be no evidence of concomitant disease in >50% of patients with paroxysmal AF.4-6 In contrast, >80% of patients with permanent AF have an identifiable underlying cause.7 The definition of chronic AF varies greatly in the literature and the terminology may be best avoided.

### Epidemiology

It is estimated that 2.2 to 5.0 million Americans and 4.5 million Europeans experience AF.1,3,8-12 The overall prevalence in the general population is estimated to be 0.4%.13 The incidence and prevalence of AF steadily increase with age, such that this arrhythmia occurs in <0.5% of the population <50 years of age and increases to approximately 2% at ages 60 to 69 years, 4.6% for ages 70 to 79 years, and 8.8% for ages 80 to 89 years.9,14,15 The age-adjusted prevalence of AF is higher for men than women9,10 and higher for whites ...

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