Heart vessels (coronary vessels) are the vessels that feed the heart and keep it working. In order for the heart to function in a healthy way, it must be constantly fed with blood coming from these vessels. In some cases, these vessels narrow and do not allow adequate blood flow. 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 in the heart vessels develops over a long time, the disease may go unnoticed and may manifest itself with a sudden onset of "heart attack".