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Posts Tagged ‘des’

Acute coronary syndrome  is primarily a disease of blood vessel , which perfuses  the heart.  It can even be a disorder of blood, often called vulnerable blood which predispose  for intra- coronary thrombus .

Mind you  , heart is an innocent bystander ! to the onslaught of  coronary atherosclerosis !

Hence , we  often use two terminologies .

CAD : Pure vascular (Coronary )  disease without  any structural and functional impairment of heart  ( No Angina, No myocardial damage ) Most of the asymptomatic plaques  , non flow limiting  lesions, incidentally detected by the modern coronary imaging gadgets  fall in this category.

When does  CAD becomes CAHD ?

CAHD : Coronary artery heart disease .Here not only the coronary artery is diseased , but it has it’s mission fulfilled   ie target organ either damaged structurally (STEMI, NSTEMI ) or functionally (EST positive , Chronic stable angina CSA )

Does the heart does any wrong to suffer from Acute coronary  syndrome  ?

No, it is simply not .The fault lies in one or more  of the following   .Generally at-least two these factors are enough to impede blood flow )  . They  combine to produce an ACS.

  • Blood defect
  • Vessel wall defect
  • Slowing of flow (Stasis)

This is called as Virchow’s triad   suggested over 100 years ago . Still valid in the era of per cutaneous  aortic valve implantation.

* The concept of de-linking  disorders of  coronary  vascular disease  from myocardial disease  is vital  in understanding the implications of current modalities of treatment. 

Even though we PCIs target the culprit ie blood vessel , it need to  realised , we  always fall short of real target . . .namely the heart . In coronary interventions  the catheters and wires roam around superficially over the heart  and they never even touch the heart .This is the reason PCIs are struggling to prove it’s  worthiness over medical therapy in many CAHD patients , which can reach deep  into the vessel, heart  and even every individual cells of heart.

Many (or . . . is it most ?)  Interventional  cardiologists have a bad  reputation for ” failing to look  look beyond the lesion” .  It is estimated  a vast  number  of cathlabs  and CABG theaters worldwide  are engaged in futile  attempt to restore coronary artery patency after a target organ damage is done .This is akin to building flyovers  to dead and closed highways .

Salvaging a coronary  artery and reliving a coronary obstruction is an entirely unrelated and futile  exercise to  a patient who has a problem  primarily in  musculature .

The much debated concept of  documenting  myocardial viability  , before revascularisation  died a premature death as the concept  by itself , was not viable commercially . (Viability studies   , tend to tie down the hands of device industry further , some  interventional   cardiologists began to see this concept  as an  interference to their freedom to adventure  )

Of-course , now  we have  other parameters  phenomenon  like  FFR estimation by Doppler , epicardial  -myocardial dissociation, slow  flow , no re-flow are  gaining importance.

Final message

ACS is primarily a disease of blood vessel but it’s impact is huge on heart. We need to look beyond the lesion .Restoring  a blood vessel  patency  to an ailing organ (Heart ) is not synonymous with total  cardiac intervention  and protection . There is lot more to cardiac physiology other than it’s blood flow. Heart muscle is a too complex organ to be controlled by few balloons and wires  which beat around the bush.

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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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Radiation injury to coronary artery  is rarely given a thought , in spite of   prolonged fluro-scopic time  during  many complex angioplasties.While the cardiologists are fully protected the patient’s heart takes on the brunt of the attack.

What happens to the coronary endothelium -metal interface when X -rays pass through it ?

It is well known the radiation delivered to a tissue is many times  amplified if a metal interface is present. Further , the metals can produce heat on exposure to radiation . This absorption and heat varies with different metals .

The radiation injury to coronary endothelium  could be  significantly higher with DES , as the polymer in it absorbs more radiation than the bare metal stent. This could be responsible for late complications of DES.

The above  concept (unproven though !) is  proposed  by  http://circ.ahajournals.org/cgi/content/full/104/5/e23 .In this study Gold coated coronary stents were found to be less safe than conventional stent

It may take many years to know the truths  about  radiation injury caused by  of coronary stents  .

But always remember , unproven concepts are  not synonymous with wrong concepts !

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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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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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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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When  a doctor is confronted by serious  doubt  ,  what will be the outcome for the patient  ?

Can  doubting  be beneficial for a patient ?  . It seems so ,  according to  EBM which  stresses   about statistical outcome at every turn of events in a  patient who  is critically  ill .

Is  something ,  always  better than  nothing   ?   Our  limbic  system tends to think so .  It  may not be true. But  in  dire situations ,   many  things  (Proven , unproven)  need to  be tried  however doubtful it ‘s  efficacy  may be  .This is  akin to an  emergency in an  airplane. Even here there need to be a logic.

Then ,this question  arises . How do we make  sure ,  we have a  dire situation on hand  ?

This is the key issue ,  in  the  decision making  for the   critically ill patients .  It  needs  experience ,  only experience !  Though the principle of uncertainty  is the fundamental rule in medicine ,   EBM  aims to bring some degree of certainty in medical therapeutics.

ebm evidence pci coronary

Benefits of doubting in coronary care unit.

In  a  sinking patient  with cardiogenic  shock  , try  the maximum treatment . Even if , the patient is  in severe shock  , take him to the  cath lab ,  try  open the coronary artery . Give the benefit of doubt  to him even though the chances of reviving him is less than 10%.

Risk of doubting in Coronary care unit.

A.Elderly STEMI  with SHT,(Arriving late ,  with  an unknown time  window  after an MI ) To thrombolyse or not ?  . There is  no benefit of doubt here.  Do not thrombolyse. Here , apply  the benefit of doubt against thrombolysis .

B. Chest pain with  LBBB (Thought to be new onset LBBB ) don’t ever rush to thrombolyse.  Wait for the enzyme result . Don’t try to thrombolyse your doubt , instead  thrombolyse the  confirmed thrombus !

C. Patient with persistent ST elevation following thrombolysis ,in an  otherwise asymptomatic and stable patient. Don’t  pass on  ” your doubt ” of salvaging   at least  some myocardium  by rescue PCI .Rescue  should be done before death. You can not resuscitate  dead myocytes.

Final message

The concept of   giving  the  benefits of doubt  to the patient   is a widely prevalent practice  in medicine .This concept is alive  and popular , not because it has proved effective, but because of the primitive   human perception and cognition  , namely “Something is better than nothing ” !

Common sense and logic would suggest , whenever  there is  a benefit  for doubting there would be a  equal (  or  even  more ) unmeasured  hazards and risks . This  becomes  especially  true ,  when   a   physician makes  a therapeutic move  based on doubting than on conviction .

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