[Answer] A patient comes to the emergency department complaining of palpitations and “some shortness of breath.” Cardiac monitoring is initiated and reveals the following ECG rhythm strip. The provider interprets this strip as indicating which arrhythmia?

Answer: In atrial flutter atrial contraction occurs at such a rapid rate that discrete P waves separated by a flat baseline cannot be seen on the strip. Instead the baseline continually rises and falls producing the “flutter” waves. In leads II and III the flutter waves may be quite prominent creating a “sawtooth” pattern. Because of the volume of atrial impulses the AV node allows only some of the impulses to pass through to the ventricles. In atrial flutter a 2:1 ratio is the most common (i.e. for every two flutter waves only one impulse passes through the AV node to generate a QRS complex). Ratios of 3:1 and 4:1 are also frequently seen.