Left main coronary artery disease (LMCAD) often evokes a panic reaction among cardiologists .Not every LMD deserve that re. To label it as significant, we have a criteria , that is 50% diameter stenosis. So what you do , for a tapering or narrowed left main with 40% stenosis. Isolated insignificant left main is rare *, but real incidence is not known. LMCAD is most often due to , atherosclerosis of left main coronary artery without limiting the flow.
What are the options ?
- Leave it alone, with intensive medical management assisted by high dose statin(80mg)
- Elective PCI with stenting , even though the lesion is not significant.
*If associated LAD or LCX is there decision making is easier .
How significant is a coronary stenosis ?
The significance of a coronary lesion with reference to “lumen diameter obstruction” is basically flawed. The significance of a coronary stenosis, by tradition is based on it’s hemodynamic impact ,right from the CASS days in early seventies.Unfortunately our mind set has not changed even after realising non obstructive – sub critical lesion is more prone for acute coronary syndrome. Is it not ironical to call a 40% lesion a non significant one !
So, the significance of coronary stenosis is two fold.
- Hemodynamic significance
- Clinical and pathologic significance
The former predisposes to often chronic stable angina, later likely to result in ACS.
How will you approach a apparently insignificant left main disease ?
A 40 % lesion in left main is hemodynamically not significant , but pathologically very significant.It needs intensive treatment. Plaque passification with medical approach is first choice.If the lesion morphology is eccentric, has irregular margins or involves LAD or LCX ostium doing a PCI or even a CABG is to be considered in spite of the lesion is hemodynamically insignificant .
Why , PCI is considered “not appropriate” for less tighter lesions , even though these lesions have great clinical significance ?
The answer is simple, The risks and the potential cost are more than the benefit !
And further , stents are not innocuous devices either , they always carry a risk of sudden occlusion as like a sub critical lesion !
Answer to the title question
True incidence is not known . Our experince (Class 1 c evidence) would suggest Left main disease constitutes up to 10 % of CAD.Among this one third would be hemodynamically insignificant
Handbook of Left Main Stem Disease
edited by Seung-Jung Park