Differentiating Junctional Tachycardia and Atrioventricular Node Re-Entry Tachycardia Based on Response to Atrial Extrastimulus Pacing
Benzy J. Padanilam, MD, FACC*,
Joseph A. Manfredi, MD,
Leonard A. Steinberg, MD,
Jeff A. Olson, DO,
Richard I. Fogel, MD, FACC and
Eric N. Prystowsky, MD, FACC
The Care Group, Indianapolis, Indiana
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Figure 1 Response to PAC Delivered When Junction Is Refractory
Response to premature atrial complex (PAC) delivered when junction is refractory (local atrial activation from PAC occurs at or after His activation). (A) Response in junctional tachycardia: a PAC delivered at a time the junction focus has already depolarized blocks at the atrioventricular node (AVN) and is unable to influence the immediate or the next junction beat. Solid circles represent junction focus. Black lines show conduction through AVN, His (H), and atrium (A). (B) Response in atrioventricular node re-entry tachycardia (AVNRT): a similarly timed PAC can influence the next beat of AVNRT by early engagement of the slow pathway. Black lines show conduction through AVN, His (H), and atrium (A), and red lines show PAC and its response. Although this figure shows advancement of the next beat (x-n), delay of the next beat or termination of tachycardia are also specific to AVNRT. Red arrow indicates PAC. FP = fast atrioventricular node pathway; SP = slow atrioventricular node pathway; x and x-n = H-H intervals.
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Figure 2 Response to Earlier PACs
(A) Response in junctional tachycardia (JT): the open circle represents the anticipated JT beat timing if no PAC were delivered. An early PAC advances the immediate JT beat and His timing by atrioventricular (AV) nodal fast pathway activation and JT continues. (B) Response in AVNRT: an early PAC may advance the immediate His by activation of the AV nodal fast pathway. However, that makes the fast pathway refractory and unavailable for retrograde conduction, terminating the AVNRT circuit. Red arrow indicates PAC and its response. Legends and abbreviations as in Figure 1.
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Figure 3 PAC Response in AVNRT
The premature atrial complex (PAC [S2]) timed to junctional (His) refractoriness advances the next His by 30 ms. The red arrow (A) points to the local atrial activation superimposed on the His signal. The advancement of the next His by this specifically timed PAC indicates atrioventricular node re-entry tachycardia as the mechanism. The measurements in milliseconds (ms) are H-H intervals. H = His electrogram; HBED = His bundle electrogram distal; HBEP = His bundle electrogram proximal; HRA = high right atrium; RV = right ventricle.
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Figure 4 PAC response in JT
The same patient as shown in Figure 3 had this rhythm after radiofrequency ablations for atrioventricular node re-entry tachycardia. Early PAC (S2) advances the immediate His by 44 ms, and the tachycardia continues. The red arrow (A) points to the local atrial activation on the His recording catheter that occurs before the His bundle activation. This advancement of the immediate His by a PAC with continuation of tachycardia indicates junctional tachycardia as the mechanism, and further ablations are not necessary. The measurements in milliseconds (ms) are H-H intervals. Abbreviations as in Figure 3.
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