Arterial supply of the heart

There are three arteries that run over the surface of the heart and supply it with blood (see the diagram above). There is one artery on the right side, and two arteries on the left side. The one on the right is known as the right coronary. On the left side, which is the main side, we have the left anterior descending (LAD) that runs down the front of the heart and supplies the front and main wall, and then the left circumflex that supplies the sidewall. If you look carefully, a major artery called the left main artery supplies the LAD and the circumflex.


Mild coronary artery disease

Heart blockage less than 40% is classified as mild coronary artery disease. Such blockages are clearly not causing restriction to blood flow and therefore very unlikely to be causing symptoms. It is important to note, however, that there is clear evidence here of progressive coronary artery disease and such patients need aggressive attention paid to risk factors for coronary disease (cholesterol, diabetes, smoking, blood pressure etc.), appropriate medicines, and healthy lifestyle changes such as exercise, weight loss and dietary modification. Paying close attention to these things can prevent progression of heart blockage and help to stabilize it.



A moderate amount of heart blockage is typically that in the 40-70% range. Usually, heart blockage in the moderate range does not cause significant limitation to blood flow and so does not cause symptoms. Moderate coronary artery disease is treated much in the same way as mild disease, basically attention to risk factors, medications, and healthy lifestyle modification. Occasionally, heart blockage at the higher end of the moderate range (50-70%) may require additional testing to see if it is significant or not and may be responsible for symptoms.



Severe heart blockage is typically that in the greater than 70% range. This degree of narrowing is associated with significantly reduced blood flow to the heart muscle and can underlie symptoms such as chest pain and shortness of breath. The severe heart blockage causes symptoms and are treated with placement of a stent  or sometimes bypass surgery is required in the setting of multiple severe blockages.




100% blockage in coronary artery stopping blood flowing any further and, of course, leading to a heart attack. Such a heart blockage is typically accompanied by major symptoms, and treatment needs to be given in a very timely manner.  If the treatment for this isn’t done within good time (usually the first few hours, the sooner the better), then the heart muscle may die, and once dead, cannot usually recover, which results in reduced heart pumping function and heart failure.