特発性右房拡張症に持続性心房停止を伴った1例

A case of idiopathic enlargement of right artium with persistent atrial standstill

　持続性心房停止は，心房心筋が広範囲に障害され，その機能が廃絶したために生じると考えられており，心臓弁膜症，虚血性心疾患，心筋症，神経筋疾患，アミロイドーシス，シャガス病などに合併するとされている^1）。一方，特発性右房拡張症は，右房に，負荷を与える原因疾患がないにもかかわらず，右房の著明な拡張を呈する疾患である^2）。その原因としては，先天性奇形説が有力であるが，いまだ明確ではない。両者はともに稀な疾患である。著者らは，特発性右房拡張症と持続性心房停止を合併した1例を経験した。このような例は，著者らが調査した範囲では，1例の報告^3）を認めるのみである。さらに本例では，両者の成因に拡張型心筋症が関与している可能性が強く，興味ある症例と思われたので報告する。

A 43-year-old man of idiopathic enlargement of right atrium with persistent atrial standstill was described. He was admitted to our hospital because of dyspnea and coughing. A grade 2/6 pansystolic murmur was heard at the apex. The electrocardiogram demonstrated junc-tional rhythm and absence of P wave in all leads. A chest X-ray film showed remarkable cardiac dilatation (CTR 69%). Right atrialangiography showed giant right atrium. His coronary angiograms revealed no abnormal findings. Left ventriculography showed mild dilatation and diffuse hypokinesia of left ventricle. Its ejection fraction was 0.45. The biopsy of endocardium of right ventricle revealed hypertrophy of cardiac muscle fibers and irregular size of cardiac cells. Therefore we suspected exist of dilated cardiomyopathy. Atrial electri-cal activity measured with intracardiac electrodes was absent. Moreover, atrial pacing was attempted at muti-ple sites at up to 10 mA with no response. Persistent atrial standstill was also diagnosed from above findings. This case is valuable because of the rarity of combina-tions of idiopathic enlargement of right atrium, perma-nent atrial standstill and dilated cardiomyopathy. We suspected that the degenerations of cardiac muscle including atriums and ventricles were existed in base, and they developed to enlargement of right atrium and dilated left ventricle.