Very fast regular tachycardia: 2 ECGs from the same patient. What is going on?

This was written by Magnus Nossen, from Norway, with comments and additions by SmithA 50 something smoker with no previous medical hx contacted EMS due to acute onset chest pain. Upon EMS arrival the patient appeared acutely ill and complained of chest pain. An ECG was recorded immediately and is shown below. How do you interpret the ECG?ECG#1There is a regular tachycardia with a ventricular rate of about 180 bpm. Smith comment: When there is a regular wide complex tachycardia, first assess whether it is sinus or not.  At a rate of 180, this is unlikely.  The patient is unstable.  Therefore, the first step is to cardiovert.  This can be done with adenosine or electricity.  After cardioversion, if successful, you can take a few moments to assess the 12-lead in more detail and assess the post conversion ECG.  In this analysis, it is critical to assess whether the initial depolarization is rapid or slow.  If rapid, that means that the depolarization is rapidly advancing and that it must be using conducting fibers (Purkinje fibers), and is therefore supraventricular.  Is it sinus or is it a supraventricular dysrhythmia?  Other important considerations are 1) whether is looks like a typical RBBB, LBBB, 2) whether it looks " bizarre " (meaning there are no RS complexes and, if not, whether the unipolar complexes are " concordant ' (all with the same precordial polarity), and 3) whether there is a " northwest " axis (between -90 and ...
Source: Dr. Smith's ECG Blog - Category: Cardiology Authors: Source Type: blogs