肥大型心筋症における運動負荷Tl-201心筋シンチグラフィーのWashout Rate低下の臨床的意義

Significance of decreased washout rate in hypertrophic cardiomyopathy by exercise Tl-201 myocardial scintigraphy

　肥大型心筋症（HCM）例では運動負荷Tl−201心筋シンチグラフィーで，灌流欠損や再分布がみられる場合があり，これには冠微小循環障害や線維化の関与が考えられている^1,2）。一方，本症においてinitial distributionは正常で，washout rateのみ低下する例が存在することが指摘されているが，その意味するところは，いまだ明らかではない^3）。

　この問題を明らかにする目的で，HCM例のうち運動負荷心筋シンチで肥厚部位に一致してwashout rateのみ低下を示す例の臨床的意義を検討したので報告する。

A clinical significance of decreased washout rate (WR) in hypertrophic cardiomyopathy by exercise thallium-201 myocardial scintigraphy was evaluated.

Thirty-six patients with hypertrophic cardiomyo-pathy and normal coronary angiogram were catego-rized into 3 groups according to initial distribution (ID) and WR : decreased ID group (17 patients, ID group), normal ID but decreased WR group (9 pati-ents, WR group) and normal ID and normal WR group (10 patients, N group).

Results :

①Cardio-thoracic-ratio and left ventricular end- diastolic pressure were higher in WR group than in other 2 groups.

② Resting ejection fraction and left ventricular end- diastolic volume index did not differ in three groups.

③Exercise ejection fraction was increased in N group, whereas it was not increased in ID or WR groups. It was increased in 47% of ID group, but were decreased or not changed in all patients of WR group.

In conclusion, decreased WR in patients with hyper-trophic cardiomyopathy may strongly suggest left ventricular myocardial damage.