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Posts Tagged ‘stents’

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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Life cycle of PTCA : Let us hope it do not become extinct !

Does PTCA  , a great Innovation for mankind,  is facing a threat of  extinction ?

It seems so . . . the stents  are losing its shine  in most situations. A simple evidence  . . . for that . . . can  be found in answering the following question

What drives the extensive research in biodegradable stents now ?

The simple answer is , we are fed up with the metals inside the coronary  artery. We want to get rid of it !

Too much of knowledge , often blunts our senses . Our track record clearly  reveals this fact. We needed a major study INTERHEART to tell the world   that  ,exercise is good and tobacco is bad for heart  !  Now ,we forgot a  simplest solution for  getting rid of  metal inside the coronary artery ,  which  is  “not to implant  the stent”  at all ! (Instead we do billion dollar research for making  bio – absorbable stents ,  which in the first place may not be required in the majority !

Read the related article . Does POBA has a role now ? in my site

The only situation  , where PCI   may  withstand the test of time could be in ACS (Both in STEMI and high risk NSTEMI !) PCI is cosmetic in most of the chronic coronary syndromes .

Final message

Our fight against human atherosclerosis will have to be , by medical means .PCI at best will  provide  a supportive role in selected patient group. It requires lots of common sense  and   scientific ignorance to achieve this.   Risk reduction ,  prevention , optimal   medical therapy  will have to play a dominant role in the next few decades .  This is something similar to the environmental issues we face in protecting our planet .No amount of green industry  will protect  the earth . It requires better social and  behavioral  ethics  from  mankind   and their  rulers !

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The world of  medical science is  moving in a alarming speed.In any field , speed is always dangerous ! That’s why we have speed breakers , traffic police , speed cameras , etc etc . The medical world  is flooded with new devices, drugs , procedures . Though the mankind is benefited with many of them , a equal number could do the opposite.

How to identify which is causing benefit and which doing harm ?

It is a horrible fact , this is the most difficult exercise  for the  medical academia   . . . Still worse , harm will masquerade as benefit ! Further ,  beneficial concepts are  often buried alive if  it lacks  glamor  or  commercial value (Eg: The Digoxins,)

Lay public (as well as )  the physicians   are fed with half-baked ( Often quarter baked !) medical information .Many  of the medical journals,  guidelines , sponsored  seminars  ,  some times  even text books do a clandestine  campaign  . Even after a completion of major trial,  real truths rarely  come out . Funnily ,  they call them aptly , as blinded study ! Who is blinding whom is a different issue .

So ,  in  this  new millennium , thousands of innovations are on the pipeline. These pipes are often  infested with trivial , duplicate or even  harmful  concepts waiting for a grand release into human domain.

Take the story of coronary stents

In 1977 , Gruntzig mastered the  opening  of  the obstructed coronary  arteries with a simple balloon without any add ons . That patient is still alive  without  angina  . In the next 30 years we have ridiculed (Rather , we were compelled  to ridicule it ! * Read the related article  Is  there a role for  plain balloon angioplasty ?

Technology made  it  possible to introduce a  gamut of intra coronary  devices .We used (?abused ) all sort of anticancer drugs within the tender human coronary arteries .In 2002 , we claimed to  have climbed the summit and conquered  the restenosis with DES. And in 2010 , every one knows  what is happening to DES .

The malaise is  deep rooted  in every specialty . Next  came the  Stem cell fiasco ? and more  recently huge  conflicts of interest exposed  in the  vaccines  against H1NI

Final message

Who is going to regulate the menace ?  Hmm . . . . then  . . . Who will regulate the regulators ?

Is there a way out for our patients ?  or  they  have to suffer with it  along with the disease . The later is  more realistic option !

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Total coronary artery occlusion is a common finding in CAD  especially in chronic stable angina. Normal coronary blood flow is 5 % of cardiac output  that amounts to 250-300ml/mt.At an average  heart rate of  70/mt  , each  beat  injects  about 5cc blood into the coronary circulation.This is shared between two coronary arteries.  This means , only few CC (2-3cc) of blood enters  each coronary artery with each cardiac cycle .

When one of coronary artery is totally occluded what happens to the coronary

blood flow ?

A.Total coronary blood flow  can be be  maintained   normal  at rest  as it  forms  only about 5% of cardiac output  (or it is only  slightly reduced )

B. It is believed , the unobstructed coronary artery  could receive the blood meant for the contralateral coronary artery. This  possibly explains the increased coronary artery diameter in the non obstructed artery.

C. It’s nature’s wish ,  that the  contralateral  coronary artery  shall share  50% of  it’s  blood through  collaterals if available.

D.If collaterals are not formed it , the unobstructed coronary  artery  may be over perfused with double the amount  of blood flow.

E. Some times , the collaterals steal  much more than what  the  obstructed coronary artery  deserves and make the feeding coronary artery ischemic. This is many times observed in  total RCA occlusion with well formed  collaterals  from LAD/LCX.

F.The collateral flow  in CTO also depend on whether flow is directed from LAD system to RCA or from RCA -LAD system. The LAD is better placed to assist RCA than vice versa.This is for two reasons.1.LAD blood flow is higher than RCA so it can share it.2.The driving pressure is more  from LAD -RCA , as RCA can receive  blood flow even during diastole .

F.During exertion , the coronary hemodynamics become further complex.The collateral’s are traditionally thought to be less than adequate during times of exercise.But it is more of a perception than solid scientific data.This rule  may be applicable in only certain group of patients. We know CTO patients with very good exercise tolerance who have documented collateral’s.

G.Collaterals can be either  visible or invisible by CAG. The strength of collateral circulation is not in it’s visibility but it’s capacity to dilate and  respond to neuro humoral mediators at times of  demand.  Currently  , there is lot to be desired  regarding  our knowledge about  the physiology  of visible collaterals , no need to  mention about invisible collaterals !

Final message

The above statements  are based  on logics and observations .

Is it not a  irony  in cardiac literature ,  where  thousands of articles  are coming out every month  to tackle  totally occluded coronary artery(CTOs) ,  there is  very little data   regarding the coronary hemodynamics in chronic total occlusion .   How  does a patient with CTO can manage a active life with only one functioning  coronary artery ?

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Coronary stents have revolutionised the management of CAD. Stents are metallic scaffolding devices that help keep the atherosclerotic plaque  plastered within the coronary arterial wall.Thus it gained the name angioplasty. Stents have aradial strength that  exerts a constant force on  the plaque . Since metals are unfriendly partners for coronary artery , we need to have minimum metal within the coronary artery.The stent struts weave around the lumen generally the stento/ artery area ratio should be as less as possible (15%).

But this has a trade off .The uncovered area of plaque tend to project into the lumen .This is many times not significant.But can be a problem if the plaque is very soft and bulk of the lipid core may reenter the lumen.this event is called plaque prolapse.

plaque-prolapse

What is the time taken for plaque to prolapse ?

Generally it is late event.But it can happen immediately after the procedure also.

Which type of lesions are more likely to have plaque prolapse ?

Eccentric and complex lesions especially with overhanging edges are prone for prolapse

What is the sequale ?

It can be benign.If there is a erosion due to stent struts can precipitate an ACS.It progresses into instent restnosis in many.

What is the angiographic appearnce ?

Angiographically it often appears as luminal  irregularity withi stented segment .

Many times , it may appear as a filling defect also.

Is there any specific issues in plaque prolapse in drug eluting stents ?

Coornary artery is not drugged uniformly by the drug eluting stents.In fact contact  lines of metalic struts  , through it’s micropore oozes the drug with polymer.Pathological studies have revelaed non homogenous drug penetration and resultant irregularity on the plaque surface.This could amplify the plaque penetration preferentially in few areas.

How to manage plaque prolapse ?

It should be managed as any other instent restenosis.Plaque resection with atherectomy devices has not solved the problem to the desired levels.A second stent is the most common approach advocated by the cardiologists.(Whic is not ideal though !)

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                                                    Drugs are poisons , whenever it is administered without valid purpose. it can enter human body  in many ways (Oral, intravenous, percutaneous etc ) And now we have another route namely intracoronary !

                                                   In quest for prevention of restenosis, many of the anti cancer drugs are now delivered directly inside the coronary arteries .These drugs are secreted  like a sustained release  tablet from the drug coated stents.These drugs are expected to prevent restenosis within the stented segment.But, after years of  intense debate and research  , we realised that ,  drugs  eluted from the stent  could damage the distal coronary vascular bed and coronary microcirculation.( And thus came the epidemic of acute stent thrombosis ! )

                                                The tender and sensitive coronary microvasculature  is constantly exposed to  these  powerful anticancer and immmunosuppresive  drugs .It is a great surprise , no body thought of  this dangerous drug -coronary artery interaction ! It required the genius of Renu virmani and others to point out this.

But still , the cardiology community by and large , fails to consider  this an important issue.This is proven by the fact, usage of DES is  still increasing  and used mainly as an off label indication.

Read this land mark article from circulation

picture1

http://circ.ahajournals.org/cgi/content/full/115/8/1051?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=1&author1=renu+virmani&andorexacttitle=and&andorexacttitleabs=and&andorexactfulltext=and&searchid=1&FIRSTINDEX=0&sortspec=relevance&fdate=1/1/2007&tdate=12/31/2007&resourcetype=HWCIT

 

Questions that need to be answered

  • What is the long term effects of drugging a coronary artery ?
  • Is no reflow or slow flow  more common after DES , because of the adverse drug reaction in the distal vascular bed ?
  • If a patient  with  DES  undergoes a CABG later what  would be  the impact of the  drug on the graft ? Will the functional vasodilatation   affected ?

Final message

                                  A drug , to get a legal clearance it has to undergo  hundreds of rigorous tests . Finally it is cleared for that  specific indication for which it is tested  .Just because a drug is cleared for one purpose ( Paclitaxel for malignancy ) it does not mean it is safe to use for any other  purpose for which it is deemed to be useful . Exactly the  opposite is happening   in the  the field of interventional cardiology . No body wondered to think what would be the effect of these drugs on the normal coronary endothelial cells and vasculature.Is it not a crime ,  without analysing this particular issue  , dozens of drug eluting stents have been released in the market . And now,  sounds of crying  foul is heard world wide !

Let us thank  , the so called negative forces in cardiology  for making this an  issue . In science ,  the watch dogs should bark  at  times of danger not wag the tail !

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