逆行性II型Gap現象を伴った房室結節リエントリー性頻拍の1例

A Case of Atrioventricular Nodal Reentrant Tachycardia with Retrograde Type II Gap Phenomenon

　症例は35歳，女性．頻脈発作を主訴に入院．発作時心電図はnarrow QRS型の上室性頻拍を呈していた．電気生理学的検査では，心房早期刺激法により房室結節二重伝導路を確認し，頻拍機序は房室結節リエントリー性頻拍と診断した．心室早期刺激法では基本刺激667 msecにおいて，連結期330〜310 msec間でHis-Purkinje系における室房ブロックを認めた．さらに連結期を300 msecに短縮すると室房伝導が再開し，いわゆるII型逆行性gap現象の所見を認めた．房室結節リエントリー性頻拍とII型逆行性gap現象の合併例の報告はなく稀な症例と考え報告した．

A 35-year-old female was admitted to our hospital with the complaint of palpitations. An electrocardio-gram revealed a narrow QRS tachycardia. An atrial extra stimulation study disclosed dual atrioventricular pathways. Our diagnosis was atrioventricular nodal reentrant tachycardia (AVNRT). During a ventricular extra stimulation study at the basic cycle length of 667 msec, a ventricular premature depolarization with a coupling interval of 330 msec induced a retrograde block in the His-Purkinje system, which was observed until the coupling interval declined to 310 msec. When the coupling interval reached 300 msec, the retrograde con-duction resumed. This was diagnosed as a retrograde type-II gap phenomenon. Coexistance of AVNRT and a retrograde type-II gap phenomenon is rare.