A stent missing a lesion after a PCI is referred to as geographical miss.
It can be metal missing a lesion ( in BMS )or a drug missing a lesion with DES.
Geographical miss is obviously more important with DES , as both metal and drug can miss a lesion ! (A double miss !)
Read a related article in this site. Geographical Miss : Difficult coronary Runways . . .
What are the types of geographical miss ?
Longitudinal miss is more of a technical failure (Interventionist error ) While axial miss is often a design or concept failure .
Longitudinal miss results in edge lesions ( either stent inflow or outflow lesions) .Axial miss result in discreet in-stent lesions .
Please remember , axial GM is much more common .
What is definition of axial geographical miss ?
Inadequate inhibition of intimal hyperplasia within the region of stent .
Mechanisms of geographic miss in DES era
- Stent vessel diameter mismatch (Less drug vessel contact)
- Low drug dose -Pharmacological error
- Stent radial strength more than the desired force per unit area . This excess stress effect might interfere with drug release.
- Some degree of vessel injury is needed for drugs to percolate. (A very smooth deployment may not release the drug properly )*
*A modern day cardiologist is expected not only to deploy the stent properly , he has to make sure drugs reach the target cells . What an irony cardiology can be . . . a too gentle PCI can show up a negative face ! when we want to poison selectively the atherosclerotic plaques .
What is the incidence of GM ?
In STLLR trial which looked specifically the issue of GM the incidence was very high , an astonishing 65 %
How to recognise it ?
Longitudinal miss can be identified by conventional angiography.
Axial miss is very difficult to diagnose . IVUS,ICT will help.
Many times it is an after thought when patient presents with an event.
What can we do once we recognise it ?
Unfortunately nothing much can be done to reverse the miss especially the axial ones.
longitudinal miss can be corrected by a over lapping stent .(Still , we do not know the implication of double metal doses dragging an edge of lesion !)
Can “Geographic miss” be termed as a failed PCI ?
Clinically , technically , logically and morally Yes .
But practically “No” , as GM takes much longer time to manifest as a clinical event , by then , no one would really attribute the event as procedure related . And of course , we have numerous other excuses to convince our patients.
The link to STLLR trial which gave us the startling data about GM .