1. Normal sinus rhythm
2. SVT with aberrancy and a rate-dependent left bundle branch block
This ECG has a narrow QRS complex initally, then a fast heart rate, regular rhythm and no identifiable P wave activity which suddenly turns to a wide complex in a left bundle branch block pattern. The question is the origin of the rhythm with the options being ventricular tachycardia or supraventricular tachycardia (SVT) with aberrancy (left bundle). There are no Brugada criteria met for this wide complex rhythm and it was eventually determined to be paroxysmal atrial flutter. See the Ventricular Tachycardia Review below to review the morphology criteria for VT when the QRS has a left bundle branch pattern.
