Atrial Flutter

No clinical hx. This ECG case is an exercise to find organized atrial activity. What is the rhythm?

Figure 1 - Lead II of the ECG Case

This is regular wide QRS tachycardia at a rate of about 136 bpm. 

Figure 2- Flutter waves marked

Rhythm strips will often not reveal the real rhythm. So, additional leads are needed. In this case, V1 helped.

In V1, flutter waves are marked. A wide QRS of different morphology from the rest clearly showed distinct flutter waves (red arrows) at a rate of about 250 bpm (1500/6 small squares). From there, we can march-out the flutter waves or P waves using a caliper. Another differential could be atrial tachycardia. An EP study is needed to differentiate the 2. 

Interpretation: Atrial flutter (atrial tachycardia) with RBBB vs aberrancy.