just to be a stinker, i have too seen something very similar to this, although my patient was not stable, and whatever the it was, it broke before we got to the ER. But from what i remember, it was a sinus tach with BBB, rate in the 130s, pt complaining of severe crushing chest pain, radiating to jaw and shoulder with weakness in the hand, bp was crap over nothing (62/p) etc etc... anyway, it was a classing text book sinus tach, except for the mysterious P wave, everything fell into normal parameters for it so be sinus, except, there was an INVERTED P wave .08mm preceding another up right p wave, followed by the QRS. The P waves appeared to be similar in shape. 12 lead showed a lateral wall stemi bout 3mm off baseline. i have the strip somewhere, ill have to dig it up for you all to see.