半年間に著明な心拡大を呈した若年者心筋炎の一剖検例

An autopsied case of juvenile myocarditis which showed a remarkable cardiac enlargement during the course of six months

　症例は19歳の学生で生来健康であったが，10日前に心窩部痛と呼吸困難が出現し起坐呼吸となり入院した。入院時血圧102／70mmHg，心拍数148／分，呼吸数34／分で，III音と湿性ラ音が聴取され肝を右季肋下8cmに触知した。胸部X線では半年前に比し著明な心胸比の増大と肺欝血を認めた。心エコー図では右室内腔に比し著しい左室内腔の拡大（左室拡張末期短径74mm）とびまん性の左室壁運動低下が示された。治療抵抗性で2週間後死亡した。剖検では心重冠は620gで，心房、右心室，心室中隔基部および心外膜に活動期および治癒期の炎症像が認められたが，左室自由壁では軽度の間質の線維化のみで左室の機能低下を説明しうる心筋細胞の脱落や広汎な線維化には乏しかった。左室機能低下には，拡張型心筋症の病態または心筋炎羅患後の過激な運動が関与した可能性がある。本例は，心筋炎の患者において光顕的には壊死，変性のない左室の拡大が起こりうることを示している。

A 19-year-old student was admitted for orthopnea. He had been a badminton player having no ex-perience of serious diseases until he became aware of exertional epigastralgia ten days before admis-sion.

On examination, blood pressure was 102/70 mmHg, heart rate 148, and respiration 34. A third sound and moist rales were heard. The liver was enlarged and palpable at 8 cm below the right costal margin. The titers of the virus neutralizing antibodies deter-mined on admission were all less than 32-fold. Chest roentgenogram as compared with that taken six months before admission showed a marked increase in the cardiothoracic ratio and pulmonary venous congestion. Echocardiogram showed a markedly dilated cavity of the left ventricule (LV) (LV diastolic diameter= 74 mm) compared with the cavity of the right ventricule (RV) (RV diastolic diameter = 20 mm) and diffusely impaired wall motion of the LV (fractional shortening= 9%). He died of intractable congestive heart failure two weeks after admission.

Heart weight was 620 g. The LV c avity was markedly dilated, but the thickness of the LV free wall was within normal limits. Microscopy of the both atria, the RV, and the basal ventricular septum showed acute and chronic-staged inflammation. How-ever, microscopy of the free wall of the LV showed only slight interstitial fibrosis without necrosis of the myocytes.

The marked dilatation of the LV cavity would be due to either the same mechanism as that of dilated cardiomyopathy or excessive exercise after infection with myocarditis. This case showed that LV dilata-tion without myocardial necrosis/ degeneration could develop among patients with myocarditis.