<prompt> A 63-year-old woman presents with symptoms of palpitations and atrial flutter on the ECG. Which of the following is the most likely mechanism of this arrhythmia?atrial asystoleatrial bigeminyright atrial macro-reentryAV nodal reentry  <response>: Atrial flutter is characterized by regular atrial activation with an atrial rate of 240 beatsmin. The ventricular response depends on the conduction of the AV node, usually there is 2:1 or 3:1 conduction. It is now known that the predominant mechanism for atrial flutter is right atrial macro reentry with circular activation. Atrial flutter typically originates from the right atrium and most often involves a large circuit that travels around the area of the tricuspid valve. This type of atrial flutter is referred to a typical atrial flutter. Less commonly, atrial flutter can result from circuits in other areas of the right or left atrium. 