![]() ![]() Other sites of initiating foci may be recorded in the left atrial appendage, left atrial wall, or along the crista terminalis in the right atrium. ![]() 16 Although most triggering foci that are mapped during electrophysiologic studies occur in the pulmonary veins in patients with paroxysmal AF, foci within the superior vena cava, 17 the ligament of Marshall, 18 and the musculature of the coronary sinus 19 have been identified. ![]() 13, 14 Discontinuous properties of conduction within the pulmonary vein may also provide a substrate for reentry within the pulmonary vein itself. 15 Rapidly firing foci can often be recorded within the pulmonary veins with conduction block to the left atrium ( Fig. 13, 14 The pulmonary vein musculature of patients with paroxysmal AF demonstrates a markedly reduced effective refractory period and conduction delay. Rapidly firing ectopic foci in pulmonary veins have been shown to be the underlying mechanism of most paroxysmal AF ( Fig. Spontaneous ectopy from muscular sleeves of pulmonary veins can serve as triggers of AF. 4 The definition of chronic AF varies greatly in the literature, and the terminology is best avoided. 3 By contrast, > 80% of patients with permanent AF have an identifiable underlying cause. 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. The term lone AF refers to AF occurring in the absence of cardiac disease or other known etiologic factors, usually in relatively young individuals. When the patient has experienced two or more episodes, AF is classified as recurrent. Thus, a designation of first detected episode of AF is made on the initial diagnosis. At the initial detection of AF, it may be difficult to be certain of the subsequent pattern of duration and frequency of recurrences. AF is classified as permanent when it has failed cardioversion or when further attempts to terminate the arrhythmia are deemed futile. 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. Longstanding AF has been continuous for at least a year. 3 Paroxysmal AF is characterized by self-terminating episodes that generally last 7 days and often requires electrical or pharmacologic cardioversion. AF has been classified into four categories: paroxysmal, persistent, longstanding persistent, and permanent. ![]()
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