What is subendocardium?

Answer 1

There don't seem to be a lot of good definitions of "subendocardium" but most references describe the subendocardial layer as that supplied by the coronary arteries deep in the myocardium. Literally, it means below the endocardium so presumably is the portion of the myocardium closest to the endocadium, which is incidentally the region most likely to be affected by myocardial infarction due to the decreased cardiac blood supply in this area.