[Broad QRS complex tachykardia - what is the mechanizm?].

We present the ECG with broad QRS complex tachycardia and left bundle branch block (LBBB) morphology. There are negative P waves in inferior leads (II, III, aVF) and positive in V1 with the RP interval of 124-164 ms. The slow-slow atrioventricular nodal reentrant tachycardia (AVNRT) conducted with LBBB aberrancy was diagnosed. The differential diagnosis of slow-slow AVNRT from atrioventricular reentrant tachycardia using concealed posteroseptal accessory pathway is discussed.