Differentiating Atrioventricular Nodal Re-Entrant Tachycardia From Junctional Tachycardia

Abstract

T ypical atrioventricular nodal re-entrant tachycardia (AVNRT) is the most common supraventricular tachycardia; however, junctional tachycardia (JT) is rare and occurs mostly in children or during infusion of isoproterenol. 1,2 Distinguishing between these arrhythmias can often be challenging during electrophysiology testing. They share many common characteristics, including similar intracardiac activation patterns, similar sites of earliest activation, and typical occurrence of a His bundle deflection before the atrial and ventricular electrograms. Slow pathway (SP) modification has evolved as the first-line treatment for AVNRT with acute success rates of 95% to 98% 3,4 ; however, catheter ablation of JT has lower success rates and a higher rate of atrioventricular block.5 Previous studies have suggested that premature atrial contractions (PACs) or atrial overdrive pacing can rapidly differentiate AVNRT from JT. 2,6Editor's Perspective see p 236 Case PresentationA 72-year-old woman with a history of paroxysmal supraventricular tachycardia that was refractory to medical therapy underwent catheter ablation. During the procedure, baseline AA interval during sinus rhythm, AH interval, and HV interval were 610, 80, and 38 ms ( Figure 1A), respectively. Narrow QRS tachycardia was induced by atrial burst pacing (320 ms; Figure 1B), which was felt to be most consistent with slow/ fast AVNRT (cycle length, 380 ms; AH, 340 ms; HA, 40 ms) based on the characteristics of induction with a critically long AH interval and the response to right ventricular overdrive pacing ( Figure 1B and 1C). SP modification was performed and guided by intracardiac electrograms and fluoroscopic landmarks. After SP modification, a tachycardia spontaneously initiated during infusion of isoproterenol with a dosage of 1 μg/min at a cycle length of 540 ms, with HA and AH intervals of 40 and 500 ms, respectively, as illustrated in Figure 2A. The tachycardia could be terminated by rapid atrial pacing or PACs and would spontaneously initiate after a few sinus tachycardia beats (Figure 2A). Figure 2B demonstrates the spontaneous onset of tachycardia at faster sweep speed with initial shortening of the HH interval to 450 ms, followed by tachycardia with the HH interval of 540 ms.PACs were introduced throughout the diastolic interval beginning at 10 ms shorter than the tachycardia cycle length until the loss of atrial capture or tachycardia was terminated ( Figure 2C). A PAC that advanced the immediate His by 50 ms resulted in delaying the subsequent His by 50 ms ( Figure 2D). However, a later PAC advanced the immediate His by 40 ms, and there was no change in the following HH interval ( Figure 2E). A later PAC delivered during His refractoriness advanced the following His by 15 ms, indicating that the mechanism of tachycardia was AVNRT ( Figure 2F). This was confirmed multiple times with late-coupled PACs advancing the subsequent His activation without affecting the immediate His. Further ablation at the SP region was performed, and subsequently, no ta...

Ritmo nodal: caso clínico

“…Los ritmos de la unión se originan cuando existe un bloqueo de la actividad eléctrica del nodo sinoauricular, o cuando el impulso es menor que la automaticidad del nodo AV/haz de His. Este tipo de ritmos es característico de las personas que tienen una disfunción del nodo sinusal, en los casos de síndrome del seno enfermo, los niños pequeños y los atletas que tienen un aumento del tono vagal también pueden exhibir un ritmo de unión intermitente, especialmente durante el sueño; se informa por igual entre hombres y mujeres (17,18). Este tipo de patologías deben ser corregidas de inmediato como medida preventiva.…”

Junctional ectopic tachycardia (JET)

“…Furthermore, JET may occur during isoproterenol infusion after slow pathway ablation and failure to diagnose of this arrhythmia may lead to further unnecessary ablation with an increased risk of AV block. 1,2,21 Failure to entrain tachycardia favors a nonreentrant mechanism.…”

“…During EP study, both arrhythmias have similar intracardiac electrogram activation patterns, similar HV intervals, and similar sites of earliest activation during catheter mapping (Figure 1B), and they may also be associated with VA block. Furthermore, JET may occur during isoproterenol infusion after slow pathway ablation and failure to diagnose of this arrhythmia may lead to further unnecessary ablation with an increased risk of AV block 1,2,21 …”

Supraventricular tachycardias: differential diagnosis at bedside and in the electrophysiology laboratory

“…An atrial extrastimulus that advances the His potential immediately after it without terminating the tachycardia indicates that the retrograde fast pathway is not essential for the circuit and suggests the diagnosis of junctional tachycardia. This criterion, however, requires that no dual (or multiple) response of the AV node is present and this is not always the case . Atrial overdrive pacing has also been proposed for differentiation of JT from AVNRT with an AHHA response versus an AHA response, respectively, provided there is no dual AVN physiology in the presence of JT .…”