Coronary angiogram is a video graphic snap shot of coronary arterial lumen which is filled with radio opaque dye. This is some times called as coronary luminogram . It is a paradox , when we say normal coronary angiogram we can only mean normal coronary lumen. But generally, this can provide sufficient information regarding the status of coronary blood flow.There are three structured layers in coronary artery wall . Coronary angiogram can not give any information about the status of the intima, media or adventia .
Lesions A to F may be totally missed by conventional coronary angiogram
A patient with normal coronay angiogram can have diffuse atheroscelrosis or localised atherosclerosis within the media of coronary artery .Many times these atherosclerotic plaques grow outward into the adventia and fail to encroach upon the lumen to be detected by coronary angiogram. These plaques , even though has an hemodynamic advantage, in that it doesn’t block blood flow , has a serious risk for sudden rupture and result in an acute coronary syndrome.
So what is the message?
A normal coronary angiogram can never convey a meaning of normal coronary arteries.
A person who has a normal coronary angiogram has no guarantee that he won’t develop a coronary event in the near future.(But the the chances are very low)
If coronary angiogram has serious limitations what is the next alternative ?
Intra vascular ultra sound imaging(IVUS) can give us an idea of the coronary arterial wall anatomy. This investigation , though available for clinical application is too complex for regular use.So , you can’t subject every patient with normal CAG to an IVUS (Intra vascualar ultra sound) to confirm the normality. The best option is what we follow every day in our practice .Tell your patients with normal coronary angiogram , that they are likely to have normal coronary arteries ! don’t add up to their anxiety by saying, in spite of normal CAG still they can carry gross atherosclerosis in their arteries. Anxiety can precipitate an coronary event. Too much technical information to the patients can be counter productive. Instead advice regular life style modification, blood pressure ,diabetes, lipid control etc .
Dr.S.Venkatesan MD 