Wide Complex Tachycardia

An otherwise healthy woman in her 20's presented with tachycardia.  She had experienced palpitations and called 911.  Prehospital rhythm strips were at a rate of at least 200 (unavailable) and the medics gave adenosine at both 6 mg and 12 mg with no effect.  She was very stable with no CP, SOB, hypotension or evidence of shock.Here is the initial ED ECG:What is the diagnosis (this is pathognomonic)?  See below. (Notice that the computer incorrectly read ***Acute MI***)1. The rhythm is irregularly irregular, therefore it is atrial fibrillation2. The complexes are wide (so one might think of atrial fibrillation with aberrancy, in which case you should see RBBB or LBBB pattern, which is not there)3. It is very fast (200 bpm)4. The shortest R-R interval (between complexes 12 and 13) is about 240 ms (very short)5. The complexes look bizarre and are not uniform, as they would be with simple aberrancy.  Thus, these represent differentially pre-excited ventricular myocardium.This is atrial fibrillation in the setting of WPW, and is a dangerous rhythm which can degenerate into ventricular fibrillation.  It is more likely to degenerate if the physicians gives AV nodal blocking drugs, especially calcium channel blockers.Here is another example of this. How should this be managed?  It can be managed with medications that convert atrial fibrillation to sinus, such as procainamide or ibutilide (and others), but when you have a wide complex very fas...
Source: Dr. Smith's ECG Blog - Category: Cardiology Authors: Source Type: blogs