![]() ![]() 2 These findings explain the mechanism for the coexistence of classical cavotricuspid (CTI)-dependent AFL and incisional reentrant AFL, and the conversion from one arrhythmia to the other after development of CTI block with catheter ablation. In the absence of the functional extension of the anatomic line of block, reentry was noted to occur around the lesion alone. However, functional extension of a fixed line of block (seen in an animal model) can result in a circuit similar to typical atrial flutter where the extended line of block forms a posterior barrier. A right atrial free wall lesion, such as an atriotomy scar, might be a central obstacle around which a wavefront circulates sometimes termed incisional reentry. 2 Additional work showed that this line of block might not be limited to the intercaval region and need not be fixed (anatomic), but instead could be functional. A line of block between the superior and inferior vena cava provided an obstacle around which the wavefront could circulate and was critical in preventing short-circuiting of the AFL circuit. Reentry as the underlying mechanism of AFL was suggested by observations that although AFL induction and sustainability was difficult in the normal canine atria, it could be reliably induced and sustained in the presence of a linear atrial lesion between the venae cavae. AFL is defined here as an arrhythmia with a macroreentrant circuit (>2 cm) distinct from focal atrial tachycardias (or small circuit reentry), with subsequent centrifugal spread. Significant advances have been made in the understanding of the mechanism of AFL, its heterogeneous nature, and its treatment, which will be reviewed in this chapter. ![]() 2 AFL most often occurs in the context of structural heart disease (e.g., valvular heart disease, ischemic heart disease, cardiomyopathy), but can also manifest during an acute disease process such as respiratory infection or myocardial infarction. 1 AFL usually coexists with atrial fibrillation (AF) and is generally initiated through a transitional phase of AF. Left Atrial Atypical Flutter (No Prior Surgery)Ītrial flutter (AFL) is one of the most common cardiac arrhythmias in humans, affecting approximately 190,000 people in the United States in 2005 its prevalence is expected to increase to 440,000 by 2050 because of the increasingly older population. Right Atrial Atypical Flutter (No Prior Surgery) Noncavotricuspid Isthmus–Dependent Flutter (Atypical Flutter) Atrial Flutter as a Reentrant Arrhythmia: Lessons from Animal Studies ![]()
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