心房停止への進展が考えられた洞不全症候群の1例

A case of sick sinus syndrome, considered to develop to atrial standstill

　心房停止1,2）（atrial standstill，以下ASと略す）は心房が電気的にも機械的にも活動を示さない病態をいい，その診断には心電図上のP波欠如，右房圧記録におけるa波欠如，心房ペーシング不応等の項目を満足させることが必要である^1）。時間的経過よりASは持続性心房停止（persistent AS）と間歇性心房停止（transientAS）に分類できる^2）。ASは時に洞不全症候群（sicksinus syndrome，以下SSSと略す）との関連が問題になり，SSSの終末像としてASが出現してくる場合もいわれているが，実際にその移行過程を明らかにした報告は少ない^3〜6）。今回著者らは入院時心電図で2：1〜3：1の心房粗動を呈とし，その停止後は長期に渡って房室接合部調律の持続とP波の欠如を認め，電気生理学的検査で洞結節・房室接合部以下，さらに心房筋の広汎な障害を証明し，将来SSSからASへ進展することが考えられる1例を経験したので，若干の考察も含めて報告する。

A 25 year old man was admitted to our hospital because of diziness and bradycardia. Physical exa-mination was normal except for an irregular pulse of 90 beats/min. Chest X-ray film showed no cardio-megaly and no pulmonary congestive changes. ECG showed 2 : 1 or 3 : 1 atrial flutter on admission. After atrial flutter was terminated spontaneously, ECG revealed absent P waves, a QRS interval of 0.10 seconds, and A-V junctional rhythm with irregular R-R interval ranging from 1.20 to 2.12 seconds. At times, cardiac arrest was noted. Esophageal electro-cardiogram also failed to demonstrate atrial activity while A-V junctional rhythm continued. Mitral valve echocardiogram lacked A point, and then a waves were absent in both the right atrial and pul-monary capillary pressure recordings. Transient atrial standstill was suspected from these findings, so that electrophysiological study was performed. Rightatrial electrogram revealed complete absence of atrial activity. His bumdle electrogram revealed H-V prolongation《 80~83 msec.》 Right atrial pacing was attempted at several atrial sites, including the high lateral, middle lateral, low lateral right atrium, and low right atrial septum. Atrial activity could be elicited with stimulus strength of 3 to 5 volts. These atrial pacing thresholds were mild or moderatelyhigher than usual. After the cesation of atrial pacing at 90 beats for two minutes, the recovery time of the first beat prolonged to 8. 46 second. We conside-red that this case was sick sinus syndrome in young adult which revealed generalized disturbance of con-duction system including the atrial muscle, and would develop to atrial standstill in the near future.