This was a first for me:
Last night I recovered a post-op CABG x 2 and mitral valve replacement. Grabbed a ECG strip, glanced at it and went to work. I was busy, so I didn't have an immediate chance to analyze the strip. Anyway, as things slowed down, I had a chance to really look at the strip and I noticed that every other QRS complex was slightly smaller than the preceding one. Also, after the smaller QRS's there was a slight compensatory pause. I looked in other leads (MCL, III) and the result was the same. Also, on the artline and pleth waveforms, every other complex was smaller than the preceding one. I was somewhat puzzled when I called the oncall resident, as was he, so we got a 12-lead. I was thinking electrical alternans associated with tamponade (always assuming the worst, I hurried to double-check my chest tubes). As it turns out, the 12-lead showed atrial bigeminy. I have never encountered such a thing. Anyone have any experience with atrial bigeminy? What causes it exactly? Thanks in advance for any input.