運動負荷で誘発された迷走神経性失神の1例

A Case of Neurally Mediated Syncope Following Treadmill Exercise Testing

　52歳，女性，労作後に失神発作を繰り返し入院．安静時心電図でII,III,aV_F,V_2-6に陰性T波と1,aV_L，V_4-6にq波を認めたが，冠動脈および左室造影では異常なく，Tl心筋シンチで散在性に取り込み低下を認めた．Treadmill運動負荷終了3分後に洞停止，洞徐脈および血圧低下を伴う失神発作が出現した．Head-up Tilt試験では，Isoproterenol（0.01μg／kg／min）投与下に2：1房室ブロックから接合部調律となり，血圧も70台まで低下して失神様症状が出現，迷走神経性失神と診断した．Disopyramide 300mg／日，経口投与後の再Tilt試験は陰性であった．運動後の迷走神経性失神は30台以下の男性に多く，中年女性ではまれであるが，本例において心電図変化と迷走神経性失神との因果関係については明らかでなかった．

A 52-year old woman was referred to our hospital for several episodes of syncope following exercise. The resting electrocardiogram showed negative T waves in II, III, aV_F. V_2-6 and deep Q waves in I, aV_L, V_4-6. On her coronary angiogram there were no stenotic lesions and the left ventriculogram showed normal size and normal contraction. However. ²⁰¹Tl scintigraphy revealed scattered defects of its uptake in the left ventricle. Three minutes after submaximal treadmill exercise testing, the patient developed sinus arrest and junctional rhythm associated with syncope. The head-up tilt test during isoproterenol infusion (0.01μg/min/ kg) induced presyncope with junctional rhythm and hypotension following 2: 1 atrioventricular block. After the patient received disopyramide 300 mg/day, repeated exercise and tilt test (using the isoproterenol infusion up to 0.03μg/kg/min) results were normal. Head up tilt test was reported to be an important dignostic tool for the evaluation of exercise-related syncope. Most of the reported cases were under 40 years of age and male without obvious organic heart disease. Although the occurrence of post-exercise vagal reaction seemed to be unusual in a middle-aged woman, the relationship between the electrocardiogra-phic and scintigraphic abnormalities and neurally mediated syncope was not able to be identified.