特異な血管走行を有し運動負荷タリウム心筋シンチで陽性所見を示したsingle coronary arteryの1例

A Case with Exercise-induced Ischemia due to a Single Coronary Artery without Coronary Artery Disease

　46歳，女性．胸背部圧迫感精査目的にて入院．負荷タリウム心筋シンチでは，前・下壁領域に一過性虚血を認めた．冠動脈造影では，右冠状動脈口は存在せず，左前下行枝と，回旋枝からそれぞれ右冠状動脈領域を灌流する枝を認めた．冠状動脈の狭窄は認めなかった．虚血の機序としては，左前下行枝および右冠状動脈領域を栄養する枝が発育不良であるために起こる運動負荷時灌流量の低下と，冠状動脈間stealとが考えられた．一部のsingle cor—onary arteryの症例には，冠状動脈に狭窄はないが，狭心症を起こす症例のあることを本例は示している．

A 46-year-old female was admitted to our hospital because of exertional angina. A standard 12-lead electrocardiogram revealed atrial fibrillation with a normal ventricular response. Exercise thallium-201 emission computed tomography revealed redistribution of anterior and inferior walls without chest pain, in-dicating extensive exercise-induced ischemia. At car-diac catheterization. hemodynamics except cardiac output and cardiac index (3.03l/min, 2.10l/min/m² respectively) were normal. Left ventriculography revealed slight hypokinesis of all walls with a calcu-lated ejection fraction of 0.52. Coronary angiography showed absence of the right coronary artery, and the left coronary artery with a small left anterior descend-ing coronary artery and a well-developed circumflexartery, indicating the presence of a single coronary artery. Branches perfusing the proximal and distal portions of the right coronary artery territory originat-ed from the mid-portion of the left anterior descending artery and the distal portion of the circumflex artery, respectively. Neither organic stenosis nor acetyl-choline-induced spasm were documented on coronary angiography. Unique features of this case are the type of the anomalous pattern of the single coronary artery and exercise-induced ischemia without coronary artery disease, from which a decreased left ventricular func-tion is considered to result. This was observed although it has been shown that typical angina does not occur in patients with a single coronary artery without coexist-ing coronary artery disease. As mechanisms of exercise -induced ischemia, we considered coronary steal phe-nomenon and/or an imbalance between the size of coronary artery and its territory.