心不全症状がマスクされ，致死的不整脈の繰り返しが前景に現れた急性心筋炎の1例

A Case with Acute Myocarditis Presenting Succession of Fatal Arrhythmia Masking Cardiac Pump Failure

要旨　症例は58歳，男性．2007年11月に何ら先行症状なく，突然の頻回失神発作にて緊急入院した．生命徴候は保たれ，心電図では心拍数毎分100回でPQ間隔は0.36秒と延長し，2枝ブロックを呈していた．心エコー図では左室前壁と下壁での軽度の壁運動低下のみで，左室駆出率は48%であった．心筋トロポニンTは陽性で，CKは244 IU/lと軽度上昇していた．入院直後に完全房室ブロックを来し，体外式ペースメーカーを留置した．入院翌日より非持続性心室頻拍を繰り返し，入院5日目には心室細動が出現した．心臓カテーテル検査では，冠動脈に有意狭窄はなく，右室心内膜心筋生検にて急性心筋炎と確定診断された．経過中心ポンプ失調に伴う心不全症状は顕在化せず，各種不整脈は消失して入院16日目に退院した．致死的不整脈を呈する症例の原因心疾患として，例え心筋障害や心ポンプ失調の臨床像がマスクされていても，急性心筋炎を除外してはならない．

　A 58-year-old man was admitted to the hospital in November, 2007, due to repeated loss of consciousness. His vital signs remained within normal range and mechanical heart failure was not distinguished. His electrocardiogram showed prolonged PQ interval with two bundle branch blocks. This echocardiogram revealed that left ventricular wall motion was mildly hypokinetic with an ejection fraction level of 48%. Immediately after admission he had syncope together with complete atrioventricular block, leading to the functioning of his temporary back-up pacemaker. Short-run type of ventricular tachycardia was sometimes observed from day 2 and, finally, ventricular fibrillation occurred on day 5. Cardiac catheterization on day 6 demonstrated his coronary artery was quite normal and right ventricular endomyocardial biopsies documented active myocarditis. Cardiac pump failure was not apparent and masked by arrhythmic events during his stay in the hospital. Even the fatal arrhythmias also spontaneously disappeared within two weeks after the onset.

　It is important to be aware of acute myocarditis as a basic heart disease in cases in which a fatal arrhythmia event occurs, even if symptomatic cardiac pump failure is not obvious.