Transition from two wide to a narrow QRS complex tachycardia: What is the mechanism of tachycardia and transition?

Simultaneous narrow and wide QRS complex tachycardia: Misdiagnosis or missed diagnosis?

“…We should have performed retrograde activation of the HB signal would exclude AVNRT with antegrade bundle branch block as a mechanism for a WCT and would have been appropriate to perform ablation targeting at the distal LB branch in a current patient with WCT of LBBB morphology despite this discordant findings. 42 Regardless of the mechanism, this case illustrates the importance of assessing the response to multiple different pacing maneuvers in determining the mechanism of either NCT or WCT, 43 rather than relying upon a single maneuver, even one that is believed to be diagnostic.…”

Wide complex tachycardia with negative precordial concordance: All that glitters is not gold

“…A WCT may result from supraventricular tachycardia (SVT) with bundle branch block (pre‐existing or tachycardia‐related), SVT with atrioventricular conduction over an accessory pathway (AP), or ventricular tachycardia (VT) 1–8 . Double tachycardia is uncommon but should always be in differential diagnosis in the presence of CL or QRS morphology change.…”

Widening of the QRS complex during the wide complex tachycardia: What is the mechanism?

“…However, the bystander pathways may show intermittent or varying degrees of pre‐excitation, and some patients may have both bundle branch aberrancy and a bystander pathway or multiple pathways, giving rise to varying degrees of QRS fusion 8 . It is sometimes complicated to differentiate from the AVNRT with BBB aberrancy than orthodromic nodoventricular (NV) or nodofascicular (NF) reentrant tachycardia (NFRT/NVRT) with BBB 22–25 . However, the dissociation of HB potential from ongoing tachycardia favor AVNRT with BBB aberrancy for f‐WCT (Figure 2).…”