Conclusion
We described a case of adenosine-sensitive AT originating from the para-Hisian region with a SCZ in the anteroseptal LA. The SCZ of the AT circuit may be located in the LA even if the earliest atrial activation is observed at the HBE among the electrodes initially placed. Even from the LA, a manifest entrainment guided ablation strategy can be a reasonable option to minimize the potential risk of AV block.
Figure 1
A: The twelve-lead electrocardiography revealed a long-RP, narrow QRS, regular tachycardia with a heart rate of 132 beats/min. The P-wave morphologies were positive in leads aVL and V1 and biphasic (negative/positive) in leads II, III, and aVF. B: Ventricular burst pacing during the sinus rhythm revealed ventriculoatrial (VA) dissociation. C: The difference in the postpacing ventriculoatrial interval between the high right atrium (HRA) and proximal coronary sinus (CS) entrainment pacing was 44ms > 14ms, indicating the absence of VA linking. D: A 4-mg bolus injection of adenosine5-triphosphate (ATP) terminated the supraventricular tachycardia without atrioventricular block. d = distal; HBE = His-bundle electrode; RVA = right ventricular apex; p = proximal; S = stimulation.
Figure 2
A: Activation maps during the tachycardia. The earliest activation site in the right atrium (EAS-RA), noncoronary aortic sinus (EAS-NCS), and left atrium (EAS-LA) are indicated. The blue star (site A) shows the pacing site where manifest entrainment was observed. The red tag (site B) indicates the successful ablation site. B: The local atrial electrograms of the EAS-RA, EAS-NCS, EAS-LA, site B, and site A during the AT preceded that of the CS proximal electrode by 35 ms, 41 ms, 44 ms, 36 ms and 32 ms respectively. AP = anterior-posterior; PA = posterior-anterior; SVC = superior vena cava; RA = right atrium; NCS = noncoronary aortic snus; LA = left atrium; MVA = mitral valve annulus; TVA = tricuspid valve annulus; MAP = mapping catheter. The other abbreviations are as in Figure 1.
Figure 3
A: Entrainment pacing from site A. The cycle lengths of the tachycardia and pacing are 455ms and 440ms respectively. The red arrows indicate the orthodromic atrial activation, and the red asterisks indicate the last orthodromic captured electrograms. The blue arrows indicate the antidromic atrial activation, and the blue asterisks indicate the last antidromic captured electrograms. B: Schematic representation of manifest entrainment from site A. The antidromic wavefront (n) captures the coronary sinus (CS), and the orthodromic wavefront of the previous beat (n-1) exits from the slow conduction zone of the reentrant circuit and captures the high right atrium (HRA) and His bundle electrode (HBE), and propagates to the ventricle. C: Schematic representation of a reset of the AT by a premature atrial complex (PAC). A PAC captures the AV node before the tachycardia wavefront exited from the SCZ. AVN = atrioventricular node; TV = tricuspid valve; MV = mitral valve. The other abbreviations are as in the previous figures.
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