Cardiac vessels (coronary arteries) are the vessels that supply the heart and ensure its functioning. In order for the heart to function properly, it must be continuously supplied with blood from these vessels. In some cases, these vessels narrow and do not allow enough blood to pass through. Thus, the heart's need for blood cannot be met and chest pain begins. We call this "coronary heart disease". Although this narrowing and blockage of the heart vessels develops over a long period of time, the disease may not be recognised and may manifest itself with a sudden "heart attack".