Intermittent orthodromic capture of the earliest activation site during atrial pacing in a case with reentrant atrial tachycardia originating from the atrioventricular node vicinity

Figures

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  FIGURE 1. (A) ECG showing sinus rhythm at 42 beats/min. (B) ECG showing narrow QRS tachycardia at 97 beats/min. (C) Induction of tachycardia with atrial extrastimulation (S1–S1: 500 ms, S1–S2: 350 ms) irrespective of AV block. CS, coronary sinus; HRA, high right atrium; RVA, right ventricular apex; S, stimulation. (D) An inverse relationship was observed between the coupling interval of atrial extrastimulation (S1–S2) and the return cycle of the first tachycardia beat (S2‐Ae). AV, atrioventricular; ECG, electrocardiogram

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  FIGURE 2. (A) Induction of tachycardia during constant ventricular pacing (S1–S1: 750 ms) with a V‐A‐A sequence. (B) Constant pacing (S1–S1: 520 ms) from the RAA during tachycardia. The tachycardia cycle length was 540 ms. RA‐FW 1–2 was constantly captured antidromically. However, the earliest atrial activation site (EAAS = His1‐2) was orthodromically (red circle) and antidromically (blue square) captured at a ratio of 3:1. The electrogram morphology at the EAAS was different between the orthodromically and antidromically captured electrograms during pacing. Moreover, the interval between the S1 and orthodromically captured electrogram (red numerical data) was gradually prolonged. RA‐FW indicates free wall of the right atrium. EAAS, earliest atrial activation site; RAA, right atrial appendage

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  FIGURE 3. (A) Constant pacing (S1–S1: 550 ms) from the high ALRA during tachycardia. The tachycardia cycle length was 600 ms. RA‐FW was constantly captured antidromically. However, the EAAS was orthodromically (red circle) and antidromically (blue square) captured alternately. The electrogram morphology at the EAAS also showed alternans. (B) RF application immediately terminated the tachycardia. ABL indicates ablation catheter. (C) Activation map during the tachycardia with the anatomical location. * indicates the location of the high ALRA. ALRA, anterolateral right atrium; EAAS, earliest atrial activation site; RF, radiofrequency