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?: (A) atrial asystole, (B) atrial bigeminy, (C) right atrial macro-reentry, (D) AV nodal reentry
Answer is C. Atrial flutter is characterized by regular atrial activation with an atrial rate of > 240 beats/min. 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.