Long-RP supraventricular tachycardia: What is the mechanism?

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

“…13 The presence of 2:1 VA block during f-WCT (Figure 1) immediately ruled out the orthodromic reentrant tachycardia (ORT) or atrial tachycardia (AT), [14][15][16][17][18] because more ventricular than atrial activations are present. [19][20][21] As the HV interval was the same between the f-WCT and SR, the remaining possibilities for f-WCT include AV nodal reentrant tachycardia (AVNRT) with aberrancy. 16 J Cardiovasc Electrophysiol.…”

“…The electrocardiogram morphology was not compatible with any known pre‐excitation pattern and no antegrade accessory pathway conduction was noted during atrial pacing at baseline 13 . The presence of 2:1 VA block during f‐WCT (Figure 1) immediately ruled out the orthodromic reentrant tachycardia (ORT) or atrial tachycardia (AT), 14–18 because more ventricular than atrial activations are present 19–21 . As the HV interval was the same between the f‐WCT and SR, the remaining possibilities for f‐WCT include AV nodal reentrant tachycardia (AVNRT) with aberrancy 16 .…”