Editing Atrial flutter (section)

==Pathophysiology==
Atrial flutter is caused by a [[Cardiac arrhythmia#Re-entry|re-entrant rhythm]]. This usually occurs along the cavo-tricuspid isthmus of the right atrium though atrial flutter can originate in the left atrium as well. Typically initiated by a [[Premature atrial contraction|premature electrical impulse arising in the atria]], atrial flutter is propagated due to differences in [[Refractory period (physiology)|refractory periods]] of atrial tissue. This creates electrical activity that moves in a localized self-perpetuating loop, which usually lasts about 200 milliseconds for the complete circuit. For each cycle around the loop,  an electric impulse results and propagates through the atria.{{citation needed|date=January 2021}}

The impact and symptoms of atrial flutter depend on the heart rate of the affected person. Heart rate is a measure of ventricular rather than atrial activity. Impulses from the atria are conducted to the ventricles through the [[AV node|atrio-ventricular node (AV node)]]. In a person with atrial flutter, a 12-lead [[electrocardiogram|electrocardiogram (ECG)]] will demonstrate the atrial chambers of the heart contracting at a rate of 280–300 beats per minute whereas the ventricular chambers of the heart typically beat at a rate of 140–150 beats per minute.<ref name="Link2012"/> Due primarily to its longer refractory period, the AV node exerts a protective effect on heart rate by blocking atrial impulses in excess of about 180 beats/minute, for the example of a resting heart rate. (This block is dependent on the age of the patient and can be calculated roughly by subtracting patient age from 220).  If the flutter rate is 300 beats per minute, only half of these impulses will be conducted, giving a ventricular rate of 150 beats per minute, or a 2:1 [[heart block]].  The addition of rate-controlling drugs or conduction system disease can increase this block substantially<ref>{{cite web |url= https://www.lecturio.com/concepts/atrial-flutter/ | title= Atrial Flutter | website= The Lecturio Medical Concept Library |access-date= 3 July 2021}}</ref>