An irregular supraventricular tachycardia: What is the mechanism?

Dual 1:2 tachycardia: What is the mechanism?

“…The differential diagnosis of the NCT with a P:R ratio of 1:2 was (a) atrial bigeminy with a low voltage P wave masked by the preceding T wave, (b) junctional bigeminy, (c) atrioventricular nodal reentrant tachycardia (AVNRT) with 2:1 retrograde block, and (d) the dual atrioventricular nodal non-reentrant tachycardia (DAVNNT) (otherwise known as "double fire" tachycardia). [1][2][3][4][5] Sporadic junctional extrasystoles typically have a less predictable coupling interval to the preceding QRS complex or His potential. 4 The possibility of dual AV nodal pathways with simultaneous fast and slow conduction should be suspected in the presence of irregular paroxysmal NCT associated with marked PR changes during sinus rhythm.…”

“…The differential diagnosis of the NCT with a P:R ratio of 1:2 was (a) atrial bigeminy with a low voltage P wave masked by the preceding T wave, (b) junctional bigeminy, (c) atrioventricular nodal reentrant tachycardia (AVNRT) with 2:1 retrograde block, and (d) the dual atrioventricular nodal non‐reentrant tachycardia (DAVNNT) (otherwise known as “double fire” tachycardia) 1–5 …”

Unusual response to His‐refractory atrial premature complex: What is the mechanism?

“…Particularly, atrioventricular reciprocating tachycardia (AVRT) and atrioventricular nodal reentrant tachycardia (AVNRT) have higher prevalence, along with the fact that these two most common NQTs can occasionally be found together in a single patient 4‐6 . The transition between two NQTs could occur due to a spontaneous or induced AES, conduction block at one limb of tachycardia, or tachycardia‐induced tachycardia 7‐9 …”

“…Furthermore, AT almost always terminates with a QRS complex that a contrary finding on the facts of the present case (Figure 2). Figure 1 represented the transition of the typical AVNRT to atypical AVNRT by AES, and Figure 2 revealed a sudden shift in the anterograde slow conduction limb to the second slow AV nodal pathway 1,9 . Radiofrequency ablation delivered in the slow pathway region elicited junctional beats and resulted in tachycardia noninducibility for both NQTs.…”

Manifest 1:2 tachycardia or atrioventricular nodal reentrant tachycardia with complete ventriculoatrial dissociation

“…The differential diagnosis of the narrow QRS tachycardia (NCT) with a P:R ratio of 1:2 was (a) atrial bigeminy with a low voltage P-wave masked by the preceding T-wave, (b) junctional bigeminy, (c) AVNRT with 2:1 retrograde block, and (d) the dual atrioventricular nodal nonreentrant tachycardia (DAVNNT) (otherwise known as "double fire" tachycardia). [2][3][4][5][6][7] The 12-lead surface electrocardiography can be regarded as the "gold standard" for the detection of a suspected DAVNNT. 8 The most basic criteria for DAVNNT consists of sinus complexes giving rise to narrow QRS complexes in a 1:2 atrioventricular (AV) ratio intermittently or incessantly (one P wave is followed by two narrow QRS complexes).…”