首先，应该是 “心肌”，不是 “心机”。

脂肪间隙：
adipose tissue;
fat pad;
lipoid space.
Please note: 脂肪间隙 is not referred to gaps between fats, but the "filled-in" fat between other tissues...
https://www.proz.com/kudoz/chinese-to-english/medical-genera...

这个 “间” 不是 “心肌j间” (inter-myocardia), 而是，
(左前降支中段局部管腔) 与 (表面心肌) 之间。

左前降支中段局部管腔：
the left anterior descending artery middle section local lumen.
or,
the middle section local lumen of the left anterior descending artery.

表面心肌：
superficial myocardium.

左前降支中段局部管腔与表面心机间脂肪间隙部分消失:
Partial disappearance of the adipose tissue between the middle section local lumen of the left anterior descending artery and the superficial myocardium.
or,
Partial disappearance of the fat pad between the middle section local lumen of the left anterior descending artery and the superficial myocardium.