Mechanism and interpretation of two-for-one response to premature atrial complexes during atrioventricular node re-entry tachycardia

Abstract

Aims The response to premature atrial complexes (PACs) during tachycardia has been shown to differentiate atrioventricular nodal re-entrant tachycardia (AVNRT) from focal junctional tachycardia (JT). His refractory PAC (HrPACs) perturbing the next His (resetting with fusion) is diagnostic of AVNRT and such a late PAC fusing with the native beat cannot reset the focal source of JT. Early PAC advancing the immediate His with continuation of tachycardia suggests JT but can also occur in AVNRT due to simultaneous conduction through the AV nodal fast and slow pathways [two-for-one response (TFOR)]. The objective of this study was to evaluate the incidence and mechanism of TFOR after early premature atrial complexes (ePACs) during AVNRT and to differentiate it from the known response to ePACs during JT. Methods and results Typical AVNRT cases were diagnosed using standard criteria. We evaluated the responses to scanning PACs delivered during tachycardia in 100 patients undergoing AV node slow pathway modification for AVNRT. The responses to HrPACs and ePACs delivered from coronary sinus os or high right atrium were retrospectively reviewed. In 10 patients, ePACs advanced the immediate His with continuation of tachycardia. In all 10 cases, HrPACs advanced the next His, confirming AVNRT as the mechanism, and indicating a TFOR. Conclusion A TFOR can occur in a small number of patients during AVNRT and is therefore not diagnostic of JT. However, HrPACs always perturbed the next His in these cases, confirming the diagnosis of AVNRT and allowing for differentiation from JT.

The transition of the tachycardia from narrow to wide by a spontaneous atrial premature beat: What is the mechanism?

“…However, when an AES (irrespective of early or late coupled) perturbs the next His, this confirms the diagnosis of AVNRT and allowing for differentiation from JT 3 . In the current case, even if His potential is not clear; there was a delay in the subsequent RB and QRS by 120 msec confirming engagement of slow AV nodal pathway 3 . There was also a fixed VA linking 4 .…”

“…Whereas the principal unique maneuver in wide QRS tachycardia diagnosis is the placement of sensed AES during tachycardia; it is also a useful method to identify AVNRT from JT 2,3 . It might ease the changes of QRS morphology into wide configuration by long‐short sequence (Ashman phenomenon).…”

“…When an AES is timed to His refractoriness, any perturbation (advancement, delay, or termination of tachycardia) of the next His indicates that anterograde AV nodal slow pathway conduction is present during the tachycardia 2 . This finding would be true only in the absence of simultaneous anterograde fast and slow pathway conduction 3 . However, when an AES (irrespective of early or late coupled) perturbs the next His, this confirms the diagnosis of AVNRT and allowing for differentiation from JT 3 .…”

Persistent 2-for-1 Atrioventricular Node Anterograde Conduction During a Supraventricular Tachycardia

“… 1 , 2 It has also been described in response to premature atrial complexes during AVNRT. 3 This case adds to the unusual manifestations of TFOR and gives us extreme physiologic possibilities to ponder the question whether AVRT can exist with more ventricular than atrial activations.…”

A case series of very slow atrioventricular nodal reentrant tachycardia resembling junctional tachycardia

“…Termination of tachycardia was recognized in one patient by overdrive atrial pacing (Case 4). With regard to the response to AES, six patients showed an A‐H‐A response, while one patient (Case 1) showed atrial‐His‐His‐atrial response with the advancement of the tachycardia, likely due to a double ventricular response 3 …”