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Posts Tagged ‘drug eluting stent’

An atherosclerotic  plaque is termed  vulnerable when it’s  future behavior is unpredictable .A vulnerable  plaque has a  tendency to get occluded at any time.

Anatomically  a  vulnerable  is  present  , if the lipid core is more , fibrous cap is  thin  and  a  large lipid  core hanging eccentrically. A plaque with high temperature (Hot plaques ,febrile plaques)detected by OCT/Raman spectroscopy or thermography

Note the T cells and macrophages wage a losing battle against a metal monster !

What is the best method to calm down these vulnerable , hot ,inflamed plaques ?

A stent which scaffolds a plaque is believed to stabilse it  and  make it less vulnerable to rupture. This is the most optimistic view on coronary stenting .

Here comes  a pessimistic view !

A metal inside a coronary artery covering is  additional  threat .A metal  is   perennially  thrombogenic  ,especially the drug eluting stents which suppress the normal endothelial  function .

What  is the realistic view  ?

A stent should be used cautiously and judiciously in coronary plaques  with   high risk features  .Here  a  stent  in all probability  converts a vulnerable plaque  into a  relatively stable plaque

When stenting is done indiscriminately( without application of mind )  in stable non flow limiting lesions  stability is replaced with vulnerability.

Is it not curious to know  any angina  in a patient  who  had   PCI  for chronic  stable angina  is labeled  as unstable angina. 

Vulnerable stents

Following are typical  clinical scenarios   where stents could  carry a vulnerability  tag . 

  1. Poorly deployed  stents
  2. Properly deployed (but unnecessarily deployed especially in chronic stable angina )
  3. All Bifurcation stents
  4. Distal left main stents
  5. Stents with plaque prolapse
  6. Finally and most importantly all  drug eluting stents are considered  vulnerable ! (That’s why  our patients has to  live at the mercy of dual platelet blockers , life long.  Of course , there is no life time warranty   that  drugs do their  job properly)

And now . . .  you answer my  question !

Can  stenting convert a stable plaque  into vulnerable plaque ?

  • If  “yes’ is your answer your patients are in safe hands .
  • If  ” No”   is  your  answer ,  you are  fit to become a leading  interventional cardiologist !

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Coronary angiogram is probably the commonest invasive cardiac investigation done  world wide. It should run into millions every year. The procedure once thought dangerous  is now performed in few minutes in day care centers . While doing a  coronary angiogram  has become a minuscule task to most cardiologists, interpreting  it correctly remains a huge task !

Many  of the young cardiologists  get fascinated in   doing a coronary  angiogram and hardly spend enough time and mind in interpreting it.

Most of  us  succumb to the popular occulo  coronary reflex and describe a coronary  artery  lesions as though it is a  number game . It is very rarely we use the quantitative angiography tools available  in the machine. We need to meticulously  analyse   the length , morphology , distal flow, thrombus  , collaterals  etc . (FFR a new avatar tries to do some justice )

Calling   atherosclerois   by numbers alone,   such as  50 %  LAD  and 70 %  diagonal    20 % left main  is a huge  insult    to the deadly  & diffuse  disease process of atherosclerosis .We are paying the penalty for it .This is  the fundamental  flaw in our  reporting , that  makes every coronary intervention redundant.We must first  remember  we are looking at the lumen not the wall of coronary  artery.

Coronary  interventions is not about removing obstructions but  regression of  atherosclerosis  load within the coronary artery , prevent progression of it and ultimately reduced cardiac events and improve  survival. It  is obvious, it can not be achieved by wires and catheters alone . At best they can be adjuncts.One can  easily understand  why medical therapy  scores over wires  as it can take care of the overall disease process.

But still  ,  most* of  the  learned cardiology community  considers medical therapy   to be an adjunct to coronary intervention  , which  is  a  gross ignorance at it’s best !

* This is my perception. If  I am proven wrong ,  I am happy our patients  will be benefited !


Final message

Do not reduce  the importance of coronary angiogram   to a  farce  number game !

Do not get excited  by visualizing your patient’s  coronary artery. It may make you richer by few thousands. Realise , what you are seeing in a CAG is a fraction of coronary  circulation.

It is estimated coronary  circulation we visualize  daily in cath lab as epicardial coronary arteries  is less than  2  % of entire cross section of coronary  circulation.

This means we are 98 % blind ! ( or  2 % wise  !) .Spend  adequate  time and  mind to interpret it correctly  , so that logical and useful  ( non ) interventions can  be done .This only can make you a  true cardiac professional and your patients will respect you.


//

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Ever since coronary stents were introduced   metal market is having a  good time within human coronary arteries.The search  for the the elusive , ideal metal is still on   . . .  Nickel , stainless steel  , platinum  etc .

Some body thought , why not gold ?

For long ,  gold is known to be a good bio -compatible metal .

Two Gold stents were tried  .

  • Inflow dynamics  – AG Germany
  • Boston scientific –  NIR stent

Surprisingly , both showed   increased reactivity  with  coronary endothlium . The verdict  was  clear . Gold coated stent  was not good enough.

http://circ.ahajournals.org/cgi/content/abstract/101/21/2478?ijkey=f03f3c40dc4c5b2673d783f91c19f5ea685ed514&keytype2=tf_ipsecsha

Gold allergy

http://onlinelibrary.wiley.com/doi/10.1111/j.0105-1873.2005.00522.x/abstract

Final message

With the advent of DES ,  gold coating of stents lost it’s popularity  .Unless  new innovations happen in gold metallurgy , the  future looks bleak  for this precious metal  , at-least  in  the human coronary arteries.

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Drug eluting stents are liberally used  worldover .

It is very unfortunate ,while the jury is still confused about the role of DES  “even”  in chronic coronary syndrome ,

There has been widespread use of DES in  the   potentially hazardous    thrombotic milieu  of STEMI  . It is well known  the DES ( polymer and drug)   has a dangerous liaison  with the thrombus.

Even as the evidence base was about to accumulate against the DES in STEMI , there was  an undue haste in the use of  this stent in STEMI .

Now in 2010 the results are out the DEDICATION trial

  • The culprit is out
  • The truth exposed
  • DES kills more life than bare metal stents   during primary PCI

Read this article  ,just released in Atlanta 2010

http://www.cardiosource.com/clinicaltrials/trial.asp?trialID=1618

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First and foremost is

Avoid the procedure if  not really indicated.A lesion which  has more thrombus load  than a plaque and it is ,  subcritical and not limiting the flow  , PCI may be inappropriate  especially if the ACS is stabilised.

  • Adequate anticoagulation  along with  2b 3a blockers should be used
  • Predilatation should be minimally used or to avoided.Direct stenting preferred.
  • In primary PCI suction devices (Export etc may be useful)
  • Distal protective devices  are  “hyped up devices” rarely useful in an occasional patient with good distal vessel diameter.
  • Pseudo stent approximati(fig 1) may occur. A Layer of thrombus may get plastered between stent and the vessel wall.In the post PCI  phase , with intense anticoagulation and antiplatelet regimen this layer may get dissolved and stent  may lose it’s grip and may dislodge or migrate.Another possibility is the dead space  beneath the stent  becomes a potential site for future  thrombus and ACS.

thrombus-and-pci

Fig 1

  • To prevent this complication , high pressure inflations and Post procedure IVUS (Intra vascualr ultraound may be done to ascertain lack of thromus between stent/vessel wal  interface)
  • Drug eluting stent evoked a special concern , when used in thrombotic milleu.This , has now been  proven to be  safe

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Stents are mechanical  devices like  a  spring ,  used to  keep an artery open after a PTCA or PCI.

des-why4

                                Bare metal stents(BMS) were found to have restenois rate of about 25%.  So it was perceived a stent should have it’s own protective coat , so that it won’t get restenosed.For this the researchers thought  anti cancer drugs are ideal as they block cell proliferation and thus neovascualrisation and restenosis.Alas, they were found dismally wrong ,  after all , neointiaml proliferation is only a part of the problem of restenosis  and simple blocking of cell growth is insufficient . The issue doesn’t stop with that, the anti cancer drugs incorporated within the stent simply can not differentiate normal from abnormal cells and

DES effectively blocks the normal endothelisation over the stents and make this highly vulnerable for acute stent thrombosis .

This complication is unique to DES and can result in SCD.Further ,during the last 6 years of DES , we recognised the restenosis rate has increased form the much hyped O % to almost 15% and it’s still growing . These  complications  has made a huge question mark over the future of drug eluting stents !

des-coverage

The concept of DES may not die , but which drug it should elute should be answered ! This  again is  going to be a long battle. So it is currently   adviced,  based  on common sense ( With due respects to  those RCTs  funded by industry )

Whenever you encounter a block within the coronary artery* Ask the following  questions in sequence  ,

  • Whether we can leave it alone  with medical therapy  ,  if the answer is no , proceed  to the next step !
  • Is there a possibility for plain balloon angioplasty in a given vessel (POBA, Yes !  the concept is not dead yet !)
  • If you decide a stent is required , Will  the  bare metal  do the job ?
  • In multivessel CAD  , Did the issue of increased metal load on the  long term outcome was considered ?
  • If lesions appear complex,  should we  not strongly consider CABG as an option ?

However  if we  have the habit of  ask ing the following  question  you are likely to deviate from scientific approach  

Is it possible to put a stent  across  the block ?

Yes , will be the answer most of the time ,and the patient will invariably get one or more stents  and carry a life long  stent related problems.

*The rule does not apply in Acute coronary syndromes

Also read this letter  posted by the author published in  British medical journal

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                                Coronary artery  by pass graft surgery has become the most common cardiac surgery done world over ever since it was first introduced by Favalaro in 1969.The common indications  are, triple vessel disease and left main disease in any of the following situationsE.

Elective CABG(Non emergent)

1.Chronic stable angina

Either emergent or elective

1.Unstable angina

Emergency CABG*

1.Acute myocardial infarction.-Cardiogenic shock

2.Failed thrombolysis

3.Failed primary PCI

4.Complications during routine PCI(Cath lab crashes !  etc)

5.As an associate procedure after a  mechanical complication during MI (Septal rupture, Acute MR etc)

*In emergency situations even a single vessel disease would require a  CABG

Hybrid CABG

Combining CABG and PCI in the same patient is followed in very few centres .(Example LAD graft and RCA angioplasty)This is done in patients who have co morbid conditions who can not tolerate prolonged surgical times.Further there can be situations  one lesion is very ideal for PCI  while for other grafting is the only solution.

Controversial CABG

1.CABG as a primary revascularisation  in STEMI*

(Rarely done now , almost obsolete , primary PCI has almost replaced it  . . . but it is still  useful if performed within 6 hours of MI )

2.Incidentally detected CAD*  following routine coronary angiogram.

( *CABG for incidentally detected asymptomatic CAD is  increasing in many parts of world )

Inappropriate CABG

         If it’s triple vessel disese it must be CABG -CASS study (1980s)

                       Coronary artery surgery study (CASS) still has considerable influence among the  cardiology  community in the decision making process  for CABG , even though it is many decades old .There has been a phenomenal development in both medical as well as interventional techniques since  CASS . (Thrombolysis, Statins, ACEI, PCI  DES to name a few) .

                     When CASS study was done many decades ago,it was believed triple vessel disese constitute a  homogeneous population and  carry  the same clinical significance . For example a 90% proximal LAD , 50% RCA and 50% OM technically qualify for a CABG and unfortunately , some of them are  subjected to it even in  2008 !  Now we clearly know, it is not the number of diseased vessels  that is important, but it’s location, severity , LV function, presence or absence of diabetes . Finally , the presence of revascularisation eligible myocardium must be documented in all post MI patients . (Technically referred to viable & ischemic myocardium ).              

              Currently , with the  PCI  & medical management has grown so much, CABG should be reserved only for, critical triple vessel disese , with at least one proximally located lesion (Mostly  LAD  or Left main ), especially in diabetic individuals.

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