An interesting response to His‐synchronous ventricular stimulation: What is the mechanism of this supraventricular tachycardia?

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

“…1 The differential diagnosis for the WCT includes all causes of NCT with BBB, all causes of NCT with antegrade pre-excitation, ventricular tachycardia (VT), and antidromic (ART) and other preexcited reciprocating tachycardias. [2][3][4][5][6][7][8] Antegrade activation suggests that the mechanism of the WCT is BBB, whereas retrograde activation is consistent with either VT or antidromic tachycardia (ART). 5,9 In the current case, the HV intervals during the WCTs were fixed and normal as did in sinus rhythm excluding the VT, ART and other preexcited reciprocating tachycardias.…”

“…The differential diagnosis of a short RP NCT with the earliest atrial activation in the HB region includes atrial tachycardia (AT) originating from near the AV node, orthodromic reciprocating tachycardia (ORT) using a septal accessory pathway, typical (slow‐fast form) atrioventricular nodal reentrant tachycardia (AVNRT), junctional tachycardia and orthodromic nodo‐fascicular (NF) or nodo‐ventricular (NV) reentrant tachycardia (NFRT/NVRT) 1 . The differential diagnosis for the WCT includes all causes of NCT with BBB, all causes of NCT with antegrade pre‐excitation, ventricular tachycardia (VT), and antidromic (ART) and other preexcited reciprocating tachycardias 2–8 …”

Transient changes in QRS morphology during a narrow complex tachycardia: What is the mechanism?

“…The differential diagnosis of NCT with V‐A dissociation includes atrioventricular nodal reentrant tachycardia (AVNRT) with block in the upper common pathway (UCP), orthodromic nodo‐fascicular (NF)/nodo‐ventricular (NV) re‐entry (NFRT/NVRT) and a focal tachycardia from the proximal or distal His–Purkinje system 1–6 . Orthodromic AVRT was easily excluded because more ventricular than atrial activations are present 5–7 .…”

“…The differential diagnosis of NCT with V-A dissociation includes atrioventricular nodal reentrant tachycardia (AVNRT) with block in the upper common pathway (UCP), orthodromic nodo-fascicular (NF)/nodo-ventricular (NV) re-entry (NFRT/NVRT) and a focal tachycardia from the proximal or distal His-Purkinje system. [1][2][3][4][5][6] Orthodromic AVRT was easily excluded because more ventricular than atrial activations are present. [5][6][7] The spontaneous changes in H-H (His-His) intervals preceded and predicted changes in subsequent V-V (ventricular-ventricular) interval, confirming anterograde activation of the HPS and node-dependent tachycardias and resetting the tachycardia (Figure 1).…”