Classification Of Atrial Flutter

Macroreentrant circuits manifesting as atrial flutter may propagate around anatomic, surgical, or functional barriers. Atrial flutter is therefore a general term used to define a heterogeneous group of macroreentrant supraventricular tachyarrhythmias that may exist in either atrium.

Recognizing the many subtypes of atrial flutter and the need for a more specific system of nomenclature to facilitate sharing of new insights by investigators into the various forms of macroreentrant tachycardias, electrophysiologists proposed this new classification schema, based on electrophysiologic criteria (30):

1. Typical atrial flutter (Type 1; or isthmus-dependent) reentry depends on a zone of slow conduction in the narrow isthmus confined by the inferior vena cavae, Eustachian ridge, CS, and tricuspid annulus. It is usually counterclockwise (also known as "common" or "usual" atrial flutter [see Fig. 2A]) but may less frequently be clockwise ("atypical atrial flutter" distinguished from "true atypical atrial flutter." Counterclockwise typical atrial flutter is the most common type of atrial flutter seen clinically. It has an atrial rate of approx 300 (240-350) cycles per min, and has negative flutter waves in the inferior leads. Clockwise typical atrial flutter also has a flutter rate of approx 300 cycles per min, but the flutter waves are usually positive in the inferior leads (see Fig. 2b).

Counterclockwise Flutter

Fig. 2. Surface electrocardiograms demonstrating both clockwise and counterclockwise typical atrial flutter in the same patient. Paper speed 100 mm/s. (A) Counterclockwise atrial flutter with 4:1 and 2:1 conduction. (B) Clockwise atrial flutter with 2:1 conduction. Note the positive flutter (f) waves in aVF.

Fig. 2. Surface electrocardiograms demonstrating both clockwise and counterclockwise typical atrial flutter in the same patient. Paper speed 100 mm/s. (A) Counterclockwise atrial flutter with 4:1 and 2:1 conduction. (B) Clockwise atrial flutter with 2:1 conduction. Note the positive flutter (f) waves in aVF.

2. True atypical atrial flutter (also called Type II, "rare," or "uncommon") is a rare type of atrial flutter that describes a heterogeneous group of single macroreentrant atrial tachycardias. This includes leading circle reentry or reentry around a variety of naturally occurring anatomic boundaries. The atrial rate in true atypical atrial flutter is usually more rapid (340-440 cycles per minute) than that of typical atrial flutter, and the direction of rotation may be clockwise or counterclockwise. (see Fig. 3).

3. Incisional reentrant atrial tachycardia is macroreentry around a surgical incision. It occurs frequently in patients who have undergone surgical repair of congenital heart

Fig. 3. True atypical atrial flutter. (A) The atrial rate is 428 BPM with variable AV conduction. (B) The atrial rate is 345 BPM with high-grade AV block. (Reproduced with permission from Marriot JL, Conover MB. Advanced Concepts in Arrhythmias. 3rd ed. Mosby, St. Louis, MO, 1998, p. 123.)

disease (Mustard, Senning, Fontan, and ASD repairs). Bi-atrial anastamosis for orthotopic heart transplantation provides an ideal substrate for reentry, as the incision forms the posterior barrier to conduction and the atrium is usually enlarged to accommodate the arrhythmia circuit.

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Responses

  • maria
    Why is counterclockwise flutter more common?
    1 year ago

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