On an electrocardiogram, or ECG, both stable and unstable angina show an ST-segment depression since ischemia's limited to the subendocardium.

心电图上，稳定型和非稳定型心绞痛都显示ST段降低，因为缺血局限于心内膜下层。

If blood flow's reduced or the myocardium is thicker, blood has a harder time reaching this deeper layer just under the endocardium, called the subendocardium.

一旦血流减少或心肌变厚，血流便难以到达最深层，即心内膜下层。

Yet another is endocardial fibroelastosis, where fibrosis develops in the endocardium, the inner lining of the heart, as well as the subendocardium right under, again making the tissue less compliant.

还有另一种病因是心内膜弹力纤维增生症，即在心内膜以及心内膜下层发生了纤维化，使得心脏组织顺应性变差。