Ischemic cardiomyopathy is caused by a lack of blood supply to the heart muscle. The left ventricle of the heart pumps oxygen-rich blood all over the body, making it the strongest part of the heart. If this area of the heart muscle has reduced blood supply, it becomes too weak to push out the blood. This may cause the left ventricle to enlarge, or dilate, as blood backs up, which is called dilated cardiomyopathy.