Feeds:
Posts
Comments

Archive for April, 2017

BMS, the original stent technology with meticulous metallurgy and design has been silently replaced by the drug eluting stent (DES) for over a decade. DES was introduced to bail out BMS from perceived high rates of  restenosis . It was a fundamental flaw, we failed to give due  weightage to the multiple variables like  operator expertise, lesion morphology, patient factors that determined the restenosis  rate .

There was never a single study done in large scale that compared a well deployed BMS with a poorly deployed BMS/ DES in terms of restenosis rate.This would have clearly quantified the technical component in the  restenosis rate that brought  pseduo -bad name for BMS in early days.

Without applying mind, wrong questions were asked and tested. No body could refute a “novel concept” , when some big names in industry  suggested  we must involve an anti cancer drug to prevent cell growth and neo-vascularisation  and hence restenosis. But , in reality  the technology of DES essentially complicated the metal behavior by adding a drug and drug adhesive agent(Polymer)  to the otherwise inert metal. Further , the , metallurgy  engineers had to restart / reduplicate from the scratch since we had  already well developed stent technology for BMS . The manipulation was  to add a drug to the metal.

The  irony of DES lies in the fact it Intentionally allowed to interfere /damage the endothelial healing and make the extended anti-platelet mandatory.  Still , DES was able to rule the world backed up by hyped data  with   bloated  reduction in restenosis rate. (Now we realise  the true benefits of DES  are nil  or at best marginal or even harmful in certain subsets of ACS .Read NORSTENT Trial linked below  )

Yes DES has a concern , but its not the drug you know !, 

Off late , since the polymer was  assumed as  culprit, variety of new generation stents with disposable /Non durable /Zero poylmer were developed. Still, polymer could not be proven as true culprit , some have started blaming  the drug again. Recently, It led to one famed DES based on Paclitaxel (which has a pride of place in the Land mark SYNTAX  study ) exited the human domain  with disgrace . (I wonder can  we conclude then SYNTAX study is also become invalid !)

This study done with over 9000 patients  concluded  like this  . . .

The DES industry was (is) so powerful it could easily shrug  the challenge of truth that came out briefly  in early 2000s when DES got hit with increased  acute complications.

Now, in 2016 NORSTENT study again showed us BMS is as good as DES in all walks of CAD.  Let us see what happens , still  its very unlikely mature cardiologists do not trust BMS.

*I have a belief  (Paranoid or not time will tell !) one of the reasons  DES are strongly promoted  is to sustain DAPT market alive and kicking for a long haul !

Scenerio  in India is frightening.

While the developed countries have DES usage rate around 65 % , India leads the world with DES constituting 95% (NIC registry 2017) of all deployed stents.What a way for a poor country  to  tackle CAD , which doesn’t even have prompt prehospital Aspirin for  bulk of their ACS patients, ready to waste  its resources in DES.

India , a country Infested with an unregulated health industry  became the perfect battle  ground for abusing the stents. With direct collusion with the large hospital managements the issue got exploded recently  .The Govt was compelled to come out with urgent restrictions and price control  in the use of stents.

Funny world this. World’s richest economies  are worried about the cost and want to phase out inappropriate therapy whenever possible, its absolute arrogance most of us feel shamed to keep BMS in their cathlab.

Final message

A  good metal based flexible ,trackable , thin struted  BMS should be the default choice for coronary stenting .( We used have one , now it vanished !)It avoids unnecessary prolonged DAPT .Most importantly one BMS costs 25 % of the cost of DES   . . . think of 4 critical proximal LAD lesions of a poor man can be fixed at the cost of one DES , that’s  definite way forward. Govt of India can pass another regulation in this regard. If you think  NORSTENT is NONSENSE  let us atleaset  insist for a large scale Indian  study for BMS /DES and  Cardiological society of India has much work to do !

Future for BMS  . . . looks bright !

While the  superiority  of DES is being increasingly questioned , the concept of surface modified BMS is being tested .This I believe is a face saving way to bring back the BMS in lieu of DES. There is a distinct  possibility of many of the new generation  DES going the BVS way in the near future.

Reference 

1.Hassan AK1, Bergheanu SC, Stijnen T, van der Hoeven .J Late stent malapposition risk is higher after drug-eluting stent compared with bare-metal stent implantation and associates with late stent thrombosis.Eur Heart 2010 May;31(10):1172-80. 

2.Zhang K1, Liu T, Li JA, Chen JY, Wang J,   Surface modification of implanted cardiovascular metal stents: from antithrombosis and antirestenosis to endothelialization.J Biomed Mater Res A. 2014 Feb;102(2):588-609.

3. https://www.pcronline.com/eurointervention/114th_issue/volume-12/number-17/350/ultra-hydrophilic-stent-platforms-promote-early-vascular-healing-and-minimise-late-tissue-response-a-potential-alternative-to-second-generation-drug-eluting-stents.

4.Drug-Eluting or Bare-Metal Stents for Coronary Artery Disease NORSTENT Investigators N Engl J Med 2016; 375:1242-1252

Post-ample : Only For non believers  ( who think this article is near rubbish ) 

I am  very much  convinced DES should be superior  for the simple reason it elutes a drug and the whole world believes it works !

Do you know, what these drugs do, and what they are expected to do ! In this elegant study  by Hassan AKEur Heart J. 2010 May;31(10):1172-80.  Its proven with IVUS , DES is many fold likely to cause late stent apposition than BMS.( Thus carrying the risk long term )  Reason is simple , patchy and incomplete endothelisation on the luminal side and pathological metal vessel wall interface  in abluminal promoting late mal-apposition.

Read Full Post »

True patients* present with symptoms , please , don’t ever think all your patients  bring their coronary artery for general servicing !

Ofcourse , we are the service provider to our patients . Though  heart is a mechanical pump it can never be considered equivalent to automobile engine .

For a Heart service station equipped with 24/7 lab,  the benefits may be  more if you treat the angiogram rather than the  patient.

Let us not misunderstand the word service , please show restraint, your patients will thank you forever.

* Silent significant CAD are indeed a problem in minority that requires selective wisdom.However, we can’t be aggressive hunters for CAD in population, as there is huge cost for human hunting !

Reference

Recent article which debates the issue of PCI in CTO
http://circ.ahajournals.org/content/135/15/1382?etoc=#sec-1

Read Full Post »

Coronary artery lumen has unique character . Its well-known  LAD diameter is not constant , it tapers in its distal course.(Unlike RCA which is more tubular ) It is estimated LAD looses 15 % of its diameter for every 30mm length.Fortunately LCX has no such long course to make tapering a visible threat. (Though it may still be an Issue !)

Is there a hemodyanmic purpose for this tapering in LAD ?

Should be, God never designs anatomy without a physiological purpose.We have to find it  out.(Can it be meant for  flow acceleration as the flow is entriely diastolic in LAD while in RCA its both in systole and diastole ?_

What is the relationship between tapering angle and final distal diameter?

Schematic of an artery with a tapered angle of 0:16 .Ref XIANG SHEN Journal of Mechanics in Medicine and Biology Vol. 16, No. 8 (2016)

So, if you have a long lesion in proximal LAD and planning to stent with a 40 mm or long  stent the distal end is hyperinflated by atleast 1.5mm, if we use a non tapered stent. Though , gain of extra  diameter  in distal segments might appear attractive, this may not work to our advantage , since it defies and distorts  the natural hemodynamic flow pattern. Further , when you have tapering vessel, proximal optimisation becomes more important.

How about a tapering coronary stent ?

It should be a welcome addition to our already overflowing coronary hardware in fixing long lesions . Its still a surprise why only very few are making this type of stent.

Meril has developed a  tapered stent up to 60 mm long  (Biomime morph).It should be useful in specific lesions sub types.Its worthwhile to note  tapering stents are used more often in carotid artery .

Advantages of long tapering stent over two stents of different sizes.

  • It avoid the vulnerable overlapping zone with double metallic load.
  • Possibly cause less restenosis
  • Low risk for stent fracture
  • It reduces procedure time and of course the cost of stent by 50 %

Why the concept of Tapered stent is not that popular ?

I can only guess, probably lack of free availability and  to a certian extent ignorance as well !  However ,current status about tapering stents is expected to evolve, though many cardiologist still  feel it’s not clinicaly important issue to use a tubular stent in tapering vessel.

Alternative  interventions in tapered vessel.

  • Wall stent and other self expendable stents
  • Tapered balloon Angioplasty (Laird Am Journal of card 1996)

Experts  in this modality are  welcome to share their experience.

Reference 

1.Zubaid MC, Buller C, Mancini GB. “Normal angiographic tapering of the coronary arteries”. Can J Cardiol 2002; 18: 973-980

2.Timmins LH, Meyer CA, Moreno MR, Moore JE Jr. “Mechanical modeling of stents deployed in tapered arteries”. Ann Biomed Eng 2008; 36: 2042-2050

3.Javier SP, Mintz GS, Popma JJ, Pichard AD, Kent KM, Satler LF, Leon MB. “Intravascular ultrasound assessment of the magnitude and mechanism of coronary artery and lumen tapering”. Am J Cardiol 1995; 75: 177-180

4.Laird JR, Popma JJ, Knopf WD, Yakubov S, Satler L, White H, Bergelson B, Hennecken J, Lewis S, Parks JM, Holmes DR. “Angiographic and procedural outcome after coronary angioplasty in high-risk subsets using a decremental diameter (tapered) balloon catheter. Tapered Balloon Registry Investigators”. Am J Cardiol 1996; 77: 561-568

5. YONG-QUAN DENG, ZHONG-MIN XIE and SONG  ASSESSMENT OF CORONARY STENT DEPLOYMENT IN TAPERED ARTERIES: IMPACT OF ARTERIAL TAPERING XIANG SHEN*, Journal of Mechanics in Medicine and Biology Vol. 16, No. 8 (2016) 1640015 

Read Full Post »