VT vs SVT vs Pre excitation

74 years old patient with palpitations and history of myocardial infarction

In this ECG is present wide complex tachycardia (QRS duration >120ms) with heart rate ~180/min.


The main differential diagnosis of Wide Complex Tachycardias are:         
          a)      Ventricular tachycardia             
          b)      Supraventricular tachycardia with RBBB or LBBB        
          c)      Supraventricular tachycardia with pre excitation.

In this case, ECG findings strongly support Atrial fibrillation with LBBB (Supraventricular tachycardia with LBBB) before VT or pre excitation.

First of all the rhythm is irregularly irregular and no supraventricular activity is present. This is very typical for atrial fibrillation.QRS complexes have typical morphology for LBBB (QS in V1 and notched R wave in lead V6).

There is no electrocardiographic features for ventricular tachycardia present. No AV dissociation, no positive or negative concordance, no ugly QRS, no capture beats, no fusion beats, no extreme axis deviation, no regular rhythm.Other ECG findings on this ECG:

Poor R-wave progression is present too (R wave in lead V3 3mm) with delayed transition  (R S just in V6).

QS complexes can be seen in anteroseptal leads that correspond with history of history of old myocardial infarction.

And finally, an old ECG of the same patient was found that has identical QRS morphology with Sinus rhythm

Old ECG of same patient

Final diagnosis: Atrial fibrilation. LBBB. Old anteroseptal infarction.