Although the heart is bathed in blood, it cannot derive its own nutrition from the blood it is continuously pumping. For its own oxygen and nutrients, the head depends on blood from 3 arteries the coronary arteries. These coronary arteries arise from the aorta and include the right coronary artery (RCA) and the left main coronary artery (LMCA which in turn divides into two( branches: the left anterior descending coronary artery (LAD and the left circumflex coronary artery (LCx).
The LMCA is the most important artery of the heart supplying almost 70-80% o the heart's muscle. Of this the LAD accounts for approximately 50% of the heart') blood supply, and the LCx for 20-30%. The remaining 20-30% of the heart's blood supply comes from the RCA. An occlusion of the LMCA is almost always fatal. LAC blockage is next in seriousness, and results in severe damage to the heart. Occlusion: of the RCA and LCx, or smaller side branches of any of the coronary arteries an usually less dangerous and result in a heart attack of variable size and severity depending on the size of the artery which is blocked.