When a bloodBlood is composed of red blood cells, white blood cells, platelets, and plasma. Red blood cells are responsible for transporting oxygen and carbon dioxide. White blood cells make up our immune defense system. Platelets contribute to blood clot partially obstructs a coronary arteryThe two coronary arteries, the right and the left, form the blood network that supplies the heart with oxygen and nutrients. They are located directly on the surface of the heart and branch into smaller vessels that or one of its branches, the heart muscle supplied by this artery continues to receive oxygen, but in insufficient amounts. This precarious condition is known as unstable angina, now referred to in medical terms as Non-STEMI (Non-ST Elevation Myocardial Infarction).