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Toothbrushing Rhythm


This strip begins with a narrow-complex tachycardia, having an R-R interval
of 0.45 seconds and thus a rate of 133 per minute.   Then something happens:
what is it?  The first rhythm is replaced with a pattern characterized by
positive and negative deflections with no notches, bumps, or other defining
features.  It just goes up and down.  The only rhythms that looks like this
are ventricular flutter or SVT with aberrancy.   This pattern is too slow to be
ventricular flutter, and too featureless to be SVT.  What is this?  What is
making this pattern?
The patient was brushing his teeth, and the monitor is picking up the electrical
activity of his arm and shoulder muscles.  This is obscuring the electrical
activity of his heart.  It's not an emergency, just an odd and amusing artifact.
One must always err on the side of caution, of course, but this "event"
was witnessed.