心筋生検からみた小児期二次性心筋疾患の検討

Studies on Secondary Forms of Myocardial Disease with Special Reference to Endomyocardial Biopsy in Infants and Children

　二次性心筋疾患の診断に占める心筋生検の意義は大きい．しかし，小児期の本病態に対する心筋生検の報告は乏しい．そこで，過去10年間に取り扱った小児期二次性心筋疾患における心筋生検の診断的意義，有用性を検討した．対象は川崎病58例，各種不整脈52例，心筋炎10例，術前先天性心疾患41例，術後先天性心疾患26例，その他6例の206例であった．その結果，二次性心筋病変は各種病態下で稀ならず認められ，原発性心筋疾患との鑑別に心筋生検は有用であった．特に川崎病，不整脈の心筋障害の評価に有意義であった．二次性心筋疾患のなかには，心筋収縮能が正常でも心筋障害像の強いもの，有意の心症状で発症し不顕性心筋炎の関与が示唆されるものなど幅広いスペクトラムがある．本病態に対し，適切な経時的心筋生検や各種診断手段の総合評価を参考にきめ細かなフォローアップを行うべきである．また，心筋生検法は幼児から安全に施行できる有用な検査手段である．

In adults, the utility of endomyocardial biopsy (EMB) has been well established for the diagnosis of acute cardiac transplant rejection, anthracycline car-diotoxicity, myocarditis and certain secondary forms of cardiac diseases including amyloidosis, hemo-chromatosis, sarcoidosis and various storage diseases. Moreover, it may he useful for the evaluation of dilated, hypertrophic and restrictive forms of cardiomyopathy, as well as idiopathic arrhythmias. However, since the clinical role of endomyocardial biopsy in infants and children is less well established, we attempted to evalu-ate the usefulness and complications of endomyocardial biopsy in this age group.

During the decade from April 1980 to December 1993, 206 transvenous endomyocardial biopsy procedures were performed at our hospital on patients aged from 2 months to 19 years, 121 male and 85 female. They included Kawasaki disease (KD) 58, dysrhythmias 52, idiopathic cardiomyopathy 13, myocarditis 6. preoper-ative congenital heart disease (CHD) 41, postoperative CHD 26 and miscellaneous 6. Endomyocardial biopsies were taken from the right ventricle, and all specimens were processed routinely for light microscopy, electron microscopy and immunofluorescence microscopy.

Kawasaki disease showed residual myocardial changes such as degeneration of myocytes, interstitial fibrosis, disarray of myocytes and inflammatory cell infiltrations not noly in the acute stage but also in the chronic stage. Some cases of long-standing KD showed histologic findings compatible with chronic myocar-ditis. Latent myocarditis was detected and diagnosed in patients with syncopal attack of unknown origin with histological findings from EMB. There were higher incidences of myocardial changes in patients with ta-chyarrhythmias who showed recurrent or persistent episodes of tachycardia compared with those transient or nonrecurrent episodes. In patients with bradyarr-hythmias. hypertrophy of myocytes and degeneration were detected.

These results indicate that endomyocardial biopsy is safe and useful in infants and children for evaluation of Kawasaki disease, dysrhythmias and pre-and post oper-ative cardiac function of CIID, in addition to car-diomyopathy and specific secondary forms of myocar-dial diseases proposed as criteria in adults.

There seems to be little correlation, however, between noninvasive cardiac function and histologic findings in patients with secondary forms of myocardial disease.