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Figure 1 Continuous recordings from tracings A to B show electrocardiogram (ECG) leads I, II, V₁, V₆, and intracardiac electrogram recorded from a mapping catheter at the His bundle region (RA-AS 1 to 2, RA-AS 3 to 4, RA-AS uni), a catheter in the right atrium, a catheter at the His bundle region, a catheter within the coronary sinus, and a catheter at the right ventricular apex during intravenous administration of 12 mg adenosine in a patient with induced sustained focal atrial tachycardia originating from the non-coronary aortic sinus. Note that: 1) there is the change in the tachycardia cycle length (TCL), from 431 to 485 ms, before termination during intravenous administration of 12 mg adenosine; 2) the interval from atrium to His activation (AH interval) during the tachycardia depends on the previous TCL, which results in short AH interval with previous long TCL or long AH interval with previous short TCL; and 3) the tachycardia termination occurs without sequential atrioventricular block during sinus rhythm. AS = aortic sinus; CS = coronary sinus; HBE = His bundle region; RA = right atrium; RVA = right ventricular apex.