Altered Mental Status, Bradycardia

911 was called for an elderly woman who fell and was confused.  Medics found her unresponsive, with " convulsive " movements.  They could not find a pulse.  They performed CPR, gave epinephrine, and intubated the patient and regained a pulse, at which time she became responsive and had this prehospital ECG:On arrival, heart rate was 87 and she was hypotensive at 52/21, with a palpable pulse and cardiac function present on echo.  She was intubated (by medics), but awake and alert and nodding to questions, shaking her head " no " to chest pain, headache, or SOB.  Repeat pulse was slow and irregular.  She was non-focal and followed commands.Her heart rate dropped back down and an ECG was recorded:Thoughts??First, there are very sublte regular P-waves at a rate just over 100, seen best in lead II across the bottom.  The ventricular response is irregular and dissociated, and narrow, so there is complete AV block with variable junctional escape.And one other finding.  At conference, one of our smart faculty, Dr. Richard Gray, immediately made the diagnosis without any other clinical information, though it is very subtle.  What is it?This magnification of lead III may help, though it is still very subtle:What is that bump at the end of the QRS?The diagnosis was not suspected based on either clinical or ECG grounds.  The patient was given atropine 0.5 mg x 3 with no response.Labs were:VBG: 7.21/59/39/23Lactate: 4.8Hgb: 13.7Na: 13...
Source: Dr. Smith's ECG Blog - Category: Cardiology Authors: Source Type: blogs