When is a “Good Result”, Just Not Good Enough?
I am currently analysing the IVUS images for angiographically-guided stent placement in my trial: The Liverpool V-HEART study (Virtual-Histology Evaluation of ACS Requiring Treatment)
It is providing me with great insight into the results gained when placing a stent in a culprit lesion from an ACS presentation. The operators performed the procedure without the aid of IVUS and the stent was placed purely on their judgement of the angiographic images. It is interesting so far to see the amount of stent abnormalities seen on IVUS that may have been avoided with a bit more time and accuracy. My analogy is - you don’t buy a suit from a supermarket if you can get it “tailor-made” at Saville Row. How can you really get it right when you are using a flawed image as your guide? A blind man is glad to be led, but those that are blind in their understanding, think they see best and scorn guidance. What really is the rush with “slamdunking” the stent in and getting in and out “like a thief in the night?” It takes a while to perform a good anastomosis at CABG, so why can’t we be a bit more technical, analytical and perfectionistic about placing a foreign body in a coronary artery? It’s not like this is not important!
I am still a bit disturbed by the whole guesswork element of PCI. The operator stares at a single angiographic projection of the vessel, sighs and hums, then turns to his co-operator and says “3.0 by 26 Xience??” “What do you think?” At most there may be another angiographic shot with a balloon in place to measure the stenosis for length but for numerous reasons this is again flawed. I can confirm, for the record, that proximal and distal reference vessels that appear angiographically normal, do contain positively remodelled plaque disease with a burden of greater than 50% and an unstable composition. I have seen so many undersized, under-deployed, asymmetrically expanded, geo-graphically missed, incompletely apposed, landed in plaque stents, that I am now struggling with conventional PCI methodology.
I hear you say “But what impact do those abnormalities have on outcomes?” I don’t know the true answer to that, but we will be following up our small cohort with residual stent abnormalities closely and I hope to be able to publish some data in 2012.
If we look at the data from SYNTAX, it is clear that despite how good we think we are, we have certainly not done well in the contemporary treatment of complex three vessel disease. The three year MACE rate was 28%, repeat revascularisation rate was 19.7% with MI 7.1%. Also recently, the IVUS sub-study of Horizons showed a post-procedure stent malapposition rate due to inappropriate stent size selection or underexpansion in 35.2%. This has implications for stent thrombo-restenosis and further MACE. There may be a role here for drug-eluting, self-apposing stents that have shown promising zero malapposition rates in the APPOSITION II randomised trial. The rate of malapposition in the conventional arm was 28%.
To conclude the above rant, I would like to lay down some old data that may again prove why we are not doing things as well as we should.
If we tried to ensure that each stent deployment met the following 5 points taken from Antonio Columbo’s MILAN group criteria, The MUSIC registry and the AVID (Angiography Versus Intravascular Ultrasound Directed stent placement ) study criteria, then it is documented that they achieved an 8% re-stenosis rate in the BARE-METAL STENT ERA.
MILAN/MUSIC/AVID IVUS guided stent deployment criteria
1: COMPLETE APPOSITION OF THE STENT ALONG ITS ENTIRETY
2: SYMMETRIC EXPANSION DEFINED BY RATIO OF MIN/MAX LUMEN DIAMETER>0.7
3: IN-STENT MLA>80% OF THE AVERAGE AREA OF DISTAL AND PROXIMAL REFERENCES
4: NO MAJOR DISSECTION
5. PROXIMAL AND DISTAL STENT EDGES HAVE NO SIGNIFICANT DISEASE (CSA>50%)
Unfortunately, post-dilatation studies such as the Optimal Stent Implantation Trial found that even at 18 atmospheres post-dilatation, only 60% of stents will reach some benchmark on formal criteria.
Another sobering thought is that in the POST Registry, Dr Neil Uren from Edinburgh (a UK IVUS guru) found that in 53 stent thrombosis cases there were approximately:
50% stents expanded less than 80% (from MUSIC criteria).
50% malapposition rate.
50% inflow-outflow disease.
20% thombus.
20% edge tears.
15% plaque protrusion.
Overall 94% had IVUS abnormalities!! (There was a 30% rate of abnormality on angiography alone)
In a study of the angiographic analysis of stent geographic miss (The STLLR Trial), the rate was 66.5% in 1600 patients. I wonder what the IVUS abnormality rate would have been in this trial.
In summary, I think we can do better and provide better patient outcomes if we ignore the angiographic illusion that makes us think we did a good job and start focussing on accuracy and “made to measure” stenting. Hopefully, the next generation of OCT systems will take us into new realms and paradigms, with the hope that a stent will be for life and not just for re-intervention!
