Today, we are revisiting an ECG from the archives, with a NEW comment from Dr Ken Grauer. This ECG is worth a second look because it is a very good example of the left bundle branch block pattern. It's also a good ECG to use when discussing treatment of wide-QRS tachycardias.
This ECG demonstrates a wide complex tachycardia with classic signs of LBBB: wide QRS, QRS negative in V1 and positive in V6 and Lead I, and supraventricular rhythm. P waves are difficult, if not impossible, to discern for sure. The machine does give a P wave axis and PR interval. When evaluating a wide complex tachycardia, the patient's hemodynamic stability will initially determine treatment. All WCTs should be treated as V TACH until proven otherwise. The presence of a typical LBBB pattern makes LBBB very likely, but is not a sure thing. This patient was confirmed to have LBBB when the rate slowed, the P waves became visible, and the QRS complexes did not change.