Editing Atrial flutter (section)

==Diagnosis==
Typical atrial flutter is recognized on an electrocardiogram by the presence of characteristic "flutter waves" at a regular rate of 250 to 350 beats per minute. Flutter waves may not be evident on an ECG in atypical forms of atrial flutter. Individual flutter waves may be symmetrical, resembling p-waves, or maybe asymmetrical with a "sawtooth" shape, rising gradually and falling abruptly or vice versa. If atrial flutter is suspected clinically but is not clearly evident on ECG, acquiring a [[Lewis lead]] ECG may be helpful in revealing flutter waves.{{citation needed|date=January 2021}}

===Classification===
There are two types of atrial flutter, the common ''type I'' and rarer ''type II''.<ref>{{Cite book |author1=Surawicz, Borys |author2=Knilans, Timothy K. |author3=Chou, Te-Chuan |title=Chou's electrocardiography in clinical practice: adult and pediatric | year=2001 | publisher=Saunders | location=Philadelphia  | isbn=978-0-7216-8697-4 }}{{page needed|date=May 2018}}</ref>  Most individuals with atrial flutter will manifest only one of these.  Rarely someone may manifest both types; however, they can manifest only one type at a time.{{citation needed|date=January 2021}}

====Type I====
[[Image:AtrialFlutter12.JPG|thumb|300px|right|Type I atrial flutter, counterclockwise rotation with 3:1 and 4:1 [[AV node|AV nodal]] block.]]
[[File:Aflut.jpg|thumb|300px|Atrial flutter with a two to one block. Note the P waves hiding in the T waves in leads V1 and V2]]
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]].{{citation needed|date=February 2021}}

The reentrant loop circles the right atrium, passing through the [[cavo-tricuspid isthmus]] – a body of fibrous tissue in the lower atrium between the [[inferior vena cava]], and the [[tricuspid valve]].<ref name="Sawhney2009"/>  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.<ref name="Sawhney2009"/>
* 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.<ref name="Sawhney2009"/>
* The re-entry loop cycles in the opposite direction in clockwise atrial flutter, thus the flutter waves are upright in II, III, and aVF.<ref name="Sawhney2009"/>

====Type II====
Type II (atypical) atrial flutter follows a significantly different re-entry pathway to type I flutter, and is typically faster, usually 340–350 beats/minute.<ref name="urlAtrial Flutter: Overview - eMedicine Cardiology">{{cite web |url=http://emedicine.medscape.com/article/151210-overview |title=Atrial Flutter: Overview|work=  eMedicine Cardiology |access-date=2009-03-06| archive-url= https://web.archive.org/web/20090226110544/http://emedicine.medscape.com/article/151210-overview| archive-date= 26 February 2009 | url-status= live}}</ref> Atypical atrial flutter rarely occurs in people who have not undergone previous heart surgery or previous catheter ablation procedures. Left atrial flutter is considered atypical and is common after incomplete left atrial ablation procedures.<ref name="Garan2008">{{cite journal|last1=Garan|first1=H|title=Atypical atrial flutter|journal=Heart Rhythm|date=April 2008|volume=5|issue=4|pages=618–21|doi=10.1016/j.hrthm.2007.10.031|pmid=18325846}}</ref> Atypical atrial flutter originating from the right atrium and heart's septum have also been described.{{citation needed|date=February 2021}}