A 47-year-old male was admitted to our hospital because of faintness on complete atrio-ventricular block. Ultrasound echocardiogram and coronary angiogram showed structurally normal. Electrophysiological test showed persistent HV block with a QRS rate of 37 beats per minute. However, continuous atrio-ventricular conduction was observed during 20bpm rapid atrial pacing with a rate of 110 beats per minute repeatedly. Spontaneous atrio-ventricular block was also documented in slow sinus rate on remarkable sinus arrhythmia. A dual chamber pacemaker was implanted. The mechanism responsible for the appearance of pause-dependent block in a patient with a structurally normal heart is unknown, but may be related to a phase-4 block.

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We present a case of antidromic tachycardia with a Mahaim fiber, which has some unusual characteristics. The patient was a 45-year-old male who had Ebstein’s anomaly relapsed LBBB-form tachycardia that was terminated with Adenosine triphosphate (ATP) injection after the initial radiofrequency (RF) ablation for multiple Kent fibers of type B WPW syndrome. He was readmitted to our institute to treat this wide QRS tachycardia. The preexcitation was negative on the baseline ECG. During programmed extra atrial stimulation (aPES) , the PQ interval prolongation was associated with only that of the AH interval, and the HV interval was fixed. Therefore the QRS morphology never changed during the initial aPES. However, at the shorter coupling interval window of less than 370msec of aPES, the LBBB-form tachycardia was induced repeatedly accompanied with the disappearance of His potential. We additionally placed the multipolar catheter along with the electrophysiological tricuspid annulus and were able to determine another AV bridge with similar decrementality with AVN. Then we were able to demonstrate that the tachycardia was antidromic atrioventricular reentrant tachycardia (AVRT) , which the atrioventricular pathway antegradely involved. We performed the RF ablation targeting the local Mahaim potential. After the ablation, the local ventricular electrogram was delayed and no tachycardia was induced.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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