This is posted courtesy of Jaber Ibrahim Almajbri.  He posted it on Facebook EKG club and gave me permission to post it here.

This 20 year old has hypotension, 70/40.

What is it?

 It is irregularly irregular, so it is atrial fibrillation.  The QRS complexes are not all the same, so it is not just atrial fib with aberrancy (RBBB, LBBB, other IVCD).   Some R-R intervals are less than 160 ms, corresponding to a possible heart rate of almost 400.   The AV node cannot conduct this fast. These are conducting down an accessory pathway.

Thus, it is atrial fibrillation with WPW.

I doubt that one could really get a diastolic BP at this rate.  This case shows how fast the heart rate can be in this condition.

This can easily degenerate into ventricular fibrillation, especially if any AV nodal blocker is given.  This must be cardioverted immediately.

Then the patient will need ablation by an electrophysiologist.