刺激伝導系障害と大動脈弁閉鎖不全を合併したmyotonic dystrophyの1例

A case of myotonic dystrophy associated with intracardiac conduction abnormalities and aortic regurgitation

　患者は48歳，男性。20歳で心雑音あり。昭和62年11月心電図異常と血清CK高値を指摘されて当院へ入院し，家族歴，筋萎縮，grip myotoniaなどよりmyotonic dystrophyと診断した。胸部X線で心拡大，心電図でⅠ°およびⅡ°房室ブロックを認めた。His束心電図でAH,HV間隔ともに延長していた。心エコー図で左室肥大，左室拡大，人動脈弁硬化を認め，心機能は低下していた。心臓カテーテル検査では大動脈弁閉鎖不全（AR）を認め，右室心筋生検では心筋へ脂肪組織が浸潤していた。息子（22歳）もmyotonic dystrophyであるが，心エコー図にて大動脈弁硬化とARを認めた。myotonic　dystrophyは多彩な心合併症，特に刺激伝導系異常をしばしば伴うことが知られているが，機械的な心機能障害はまれとされている。本症例は明らかな心機能低下とARを伴うとともに，親子でARを認めた点で，興味ある症例と考えられ，その心機能障害の評価には心エコー図が有効であった。

A rare case of myotonic dystrophy with mechani-cal derangement in a 48-year-old male is reported. The patient was admitted to Fuzisawa City Hospital because of chest discomfort. On physical examina-tion, he had the typical facial appearance of myo-tonic dystrophy, and displayed grip myotonia.

The blood pressure was 120/60mmHg and the pulse 51, regular. A systolic ejection murmur at the cardiac base, an early diastolic blowing murmur along the left sternal border, and a pansystolic mur-mur at the apex were heard. The deep tendon reflexes were all normal.

Elevation of serum creatine kinase and aldolase were noted. Chest X-ray films suggested moderate cardiomegaly. An electrocardiogram showed sinus bradycardia, atrioventricular block and left bundle branch block, suggesting diffuse involvement of the conduction system. An echocardiography confirmed the presence of left ventricular enlargement, thick-ened aortic valves, mitral regurgitation, and aortic regurgitation. Selective coronary angiography re-vealed no abnormalities. Left ventriculography de-monstrated diffuse hypokinesis of the entire ven-tricle. Light microscopy of biopsied right myocar-dium revealed prominent interstitial fatty infiltra-tion, mild interstitial fibrosis, and variation in the nuclear size.

A 22-year-old son also had myotonic dystrophy and had an echocardiography indicative of thickened valves with aortic regurgitation.

Myotonic dystrophy is a autosomal dominant disease. Cardiac involvement selectively disturbs the conduction system, sinus node, and to a lesser extent myocardium. Although the presence of aortic regurgitation could be a mere coincidence, we be-lieve that this did not occur by accident, because the patient's son also had aortic regurgitation.