This is a middle aged patient who came in due to shortness of breath. No fever, no cough, no calf tenderness, no chest pain. VS 110's/60's 140 regular, afebrile sat 98% at 2L. Clear breath sounds, no murmur and no peripheral edema.
What is the rhythm?
This is a regular wide complex tachycardia (~ 150 bpm) with a right bundle branch block (RBBB) morphology. For tachycardias that are in the 150 range, think of atrial flutter. The heart rate trend or the histogram often is "flat" (or no variation in rate).
With intervention (AV nodal drugs), flutter waves will be visible. Sometimes in life the rhythms are so elusive and they will not show their classic features right away.