Atrial flutter classification
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]
Overview
Atrial flutter was previously classified as either type I or type II. That terminology is no longer used. Most individuals with atrial flutter will manifest only one of these. Rarely someone may manifest both types; however, they can only manifest one type at a time. New classification is of two types, typical and atypical atrial flutter.
Old Classification
Atrial flutter was previously classified as either type I or type II. That terminology is no longer used.
- Type I atrial flutter, also known as common atrial flutter or typical atrial flutter, has an atrial rate of 240 to 340 beats/minute. However, this rate may be slowed by antiarrhythmic agents. The re-entrant loop circles the right atrium, passing through the isthmus - a body of fibrous tissue in the lower atrium between the inferior vena cava, and the tricuspid valve. Type I flutter is further divided into two subtypes, known as counterclockwise atrial flutter and clockwise atrial flutter depending on the direction of current passing through the loop. Counterclockwise atrial flutter (known as cephalad-directed atrial flutter) is more commonly seen. The flutter waves in this rhythm are inverted in ECG leads II, III, and aVF. The re-entry loop cycles in the opposite direction in clockwise atrial flutter, thus the flutter waves are upright in II, III, and aVF.
- Type II flutter, also known as atypical flutter, follows a significantly different re-entry pathway to type I flutter, and is typically faster, usually 340–430 beats/minute. This type of atrial flutter is non-isthmus dependent and is believed to be due to an intraatrial reentrant circuit.
New Classification
Typical atrial flutter
- The designation of "typical" atrial flutter involves a macroreentrant circuit traversing the cavo-tricuspid isthmus (CTI)[1][2].
- Isthmus is the region of right atrial tissue between the orifice of the inferior vena cava and the tricuspid valve annulus. If this isthmus is involved, it is called "typical" atrial flutter or CTI-dependent atrial flutter.
- The circuit is usually a counterclockwise rotation around the tricuspid valve, exhibiting a classic sawtooth appearance in the inferior electrocardiogram (ECG) leads (II, III, aVF).
- If the circuit is clockwise, it is called "reverse" or "clockwise" typical flutter, exhibiting positive flutter waves in the inferior ECG leads.
Atypical atrial flutter
- If the CTI is not involved in the underlying mechanism, then it is called "atypical" atrial flutter.[3][4]
- This type of flutter can involve any region of the right or left atria, around areas of scar tissue due to intrinsic heart disease or surgical/ablated scar tissue. Surgical repair of congenital heart disease may lead to macroreentrant atrial flutter circuits, both typical (cavotricuspid isthmus dependent) and atypical.
- These circuits are usually right atrial, related to anatomic obstacles and surgical scars (cavotricuspid isthmus, right atriotomy scar, atrial septal defect repair, etc).
- Incomplete ablation lines created in attempts to cure atrial fibrillation with ablation can promote atypical atrial flutter circuits in the left atrium (mitral isthmus flutter, etc).
- Focal atrial tachycardias with atrioventricular block may also mimic atypical atrial flutter by ECG appearance, but by electrophysiologic study the focal mechanism can be differentiated from the macroreentry seen in atrial flutter.
References
- ↑ Bun SS, Latcu DG, Marchlinski F, Saoudi N (September 2015). "Atrial flutter: more than just one of a kind". Eur. Heart J. 36 (35): 2356–63. doi:10.1093/eurheartj/ehv118. PMID 25838435.
- ↑ Ouali S, Anselme F, Savoure A, Cribier A (June 2003). "An atypical atrial flutter of focal origin: a study using a noncontact mapping system". Pacing Clin Electrophysiol. 26 (6): 1410–2. doi:10.1046/j.1460-9592.2003.t01-1-00200.x. PMID 12822758.
- ↑ Cosío FG (June 2017). "Atrial Flutter, Typical and Atypical: A Review". Arrhythm Electrophysiol Rev. 6 (2): 55–62. doi:10.15420/aer.2017.5.2. PMC 5522718. PMID 28835836.
- ↑ Rostock T, Konrad T, Sonnenschein S, Mollnau H, Ocete BQ, Bock K, Spittler R, Huber C, Theis C (September 2015). "[Surface ECG characteristics of right and left atrial flutter]". Herzschrittmacherther Elektrophysiol (in German). 26 (3): 208–13. doi:10.1007/s00399-015-0386-2. PMID 26260681.