On the basis of this mechanism the prolonged RR

On the basis of this mechanism, the prolonged RR interval with the patient\'s symptoms was likely a reflection of the progression of the AV block with an underlying first-degree AV block. Despite a first-degree AV block (420ms) during the short RP rhythm, a short PR interval (160ms) was observed with an advanced AV block (Fig. 1B). Thus, the patient could have a dual AV sphingosine-1-phosphate pathway. The effective refractory period of the fast pathway can exceed that of the slow pathway. The functional block in the fast pathway can be maintained by repetitive collision of retrograde invasion of impulses conducted through the slow pathway (linking phenomenon) [2]. During an advanced AV block, the antegrade conduction block of the slow pathway can allow the recovery of fast pathway conduction. However, the P wave resulting in the QRS is not the one immediately in front of the QRS but the P wave before that one, conducting with a long PR, which would explain this phenomenon. After temporary pacemaker insertion, adenosine triphosphate (ATP) (100μg/kg) was rapidly administered to confirm the mechanism of the short RP rhythm (Fig. 2). Following venous administration of adenosine, an advanced AV block was observed with persistent atrial ectopic rhythm similar to that shown in Fig. 1. The prolongation of atrial cycle lengths with ATP injection may suggest that this rhythm has an automaticity mechanism. In conclusion, the present case demonstrated an ectopic rhythm with marked first-degree AV block followed by an advanced AV block resulting in the prolongation of the long RR interval.
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Acknowledgments