An adult case of junctional tachycardia diagnosed by premature atrial contractions and atrial overdrive pacing

We report an adult case with JT, which could be differentiated from slow‐fast AVNRT by premature atrial contractions and atrial overdrive pacing.

). Furthermore, a positive correlation between the S1-S2 interval and tachycardia return cycle was observed during tachycardia induction by atrial extrastimuli (Figure 2B,C), which suggested that the mechanism of this tachycardia is not reentry. The tachycardia cycle was slightly fluctuating and accelerated after the isoproterenol was administered. The earliest atrial activation site during tachycardia was recorded in the HB region. During right ventricular overdrive pacing (RVOP), an atrial activation sequence was identical to the NCT. The difference between the post-pacing interval and tachycardia cycle length corrected by an atrioventricular nodal conduction delay was 136 ms (>110 ms) with a V-A-V response after RVOP, which was less likely to be an atrioventricular reentry tachycardia or atrial tachycardia. 3,4 A spontaneous early PAC advanced the His potential immediately, and the tachycardia was still sustained ( Figure 3A). Atrial overdrive pacing (AOP) from a high right atrial site resulted in an A-H-H-A response ( Figure 3B).
Three-dimensional electroanatomic mapping during tachycardia showed that the earliest atrial activation site was located near the anterior HB region. Finally, we diagnosed the NCT as junctional tachycardia (JT) and did not perform catheter ablation, considering the risk of atrioventricular block.
The mechanism of JT is abnormal automaticity or triggered activity. 1 In the present case, tachycardia was induced by programmed atrial stimulation. Of note, the return cycle length of the tachycardia did not inversely correlate with the S1-S2, suggesting that the mechanism of this tachycardia was not reentry and also

F I G U R E 1
The 12-lead ECG shows a regular narrow QRS complex tachycardia.
25mm/sec F I G U R E 2 (A) The atrioventricular conduction curve during programmed atrial stimulation is shown. The SVT was induced by an atrial extrastimulus pacing (red circle) without a jump-up phenomenon. (B) After the last atrial-paced beat (S1-S1 = 600 ms, S1-S2 = 400 ms), the return cycle of the tachycardia was 724 ms. (C) After the last atrial-paced beat (S1-S1 = 600 ms, S1-S2 = 360 ms), the return cycle of the tachycardia was 661 ms. An inverse correlation of the return cycle was not observed. A: atrial potential, Ap: atrial pacing, CS: coronary sinus; d: distal, H: His potential, HIS: a bundle of His, p: proximal, RA: right atrium, RV: right ventricle, SVT: supraventricular tachycardia.

ACK N OWLED G M ENTS
None.

CO N FLI C T O F I NTER E S T S TATEM ENT
The authors declare that there is no conflict of interest.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data sets generated and/or analyzed during the current study are available from the corresponding author upon reasonable request.

E TH I C S S TATEM ENT
The research related to human use has complied with all the relevant national regulations and institutional policies and is in accordance with the tenets of the Helsinki Declaration and has been approved by the author's institutional review board or equivalent committee.

PATI ENT CO N S ENT S TATEM ENT
Informed consent has been obtained from all individuals included in this study.

CLI N I C A L TR I A L R EG I S TR ATI O N
None.