As a medical professional with expertise in cardiology, I can explain the causes of an NSTEMI (Non-ST-segment elevation myocardial infarction). NSTEMI is a type of heart attack that occurs when there is a partial blockage in the coronary arteries, which supply blood to the heart muscle. This partial blockage leads to a decrease in blood flow to the heart muscle, specifically causing subendocardial ischemia, which is a condition where the inner layer of the heart muscle (subendocardium) does not receive enough oxygen-rich blood. The blockage is often caused by atherosclerosis, a disease process where plaque builds up in the arteries. The plaque is made up of fat, cholesterol, and other substances in the blood that form a thick, hard deposit on the inner walls of the arteries. When this plaque ruptures or becomes unstable, it can trigger a blood clot. This clot can partially or temporarily block the blood flow through the coronary artery, depriving the heart muscle of oxygen and nutrients, leading to an NSTEMI. It's important to note that NSTEMI differs from STEMI (ST-segment elevation myocardial infarction) in that the blockage in NSTEMI is not complete, and the damage to the heart muscle is typically less severe. However, it is still a serious medical condition that requires prompt attention and treatment. read more >>

This is explained by the fact that NSTEMI and unstable angina are caused by partial (incomplete) coronary artery occlusions; a partial occlusion results in a reduction of coronary blood flow and this causes subendocardial ischemia (i.e ischemia that only affects the subendocardium).read more >>