Feeds:
Posts
Comments

Posts Tagged ‘acs’

T waves attract less  attention in STEMI ,except for the  fact   tall T waves  implies   hyper acute phase of  STEMI.

What is the duration of hyper acute phase ?

  1. Few seconds
  2. Few minutes
  3. An hour
  4. Few hours
  5. Any of the above

Answer

No one exactly knows  .It can  be highly variable .  So , 5  could be  the correct answer .  

 * Most importantly  hyper acute phase  need not occur in all patients with STEMI as suggested in experimental models.

Some  observations in T wave behavior in STEMI

Mechanism of hyper acute  T waves

It is the pottsium channel dynamics.Transient intracellular hyperkalemia  is thought to be responsible.

T wave as marker of  reperfusion

Inverted T wave in precordial leads are a good marker of IRA patency  especially in LAD

Slowly evolving STEMI

This is relatively  new concept . STEMI with a prolonged hyper acute phase  ,  ie ,  T waves ” dilly dallying”  for hours or even few days have been recognised. (This was  refered  to pre-infarction angina in the past )

This sort of T wave behavior makes it difficult to diagnose STEMI.Enzymes will help , still  thrombolytic guidelines  demand us to wait till ST elevation to occur. This is  unfortunate .But as physicians we are  justified to thrombolyse tall T waves with a clinical ACS .The other simple solution is to shift the patient to cath lab to find what exactly is happening in the LAD ! 

Now , what is new about  T waves in STEMI ?

It is  the localizing value  in LAD infarct

A tall persistent  hyper acute T wave  helps us to localise a LAD lesion .This paper from Netherlands ,  clearly  confirms this observation. The study was done from a primary PCI cohort,   a perfect setting to assess the  T wave behavior  in the early minutes /hours of  STEMI .

Other mysteries about T waves in STEMI

Does hyperacute T waves  occur in infero-posterior STEMI ?

I would believe it is very rare .Our CCU has not seen any tall T waves in inferior lead. Further analysis of the  data from the  above study could answer this question .

How often a  hyperacute T waves transform into NSTEMI ?

This again is not clear.Most of the hyper acute T will evolve as STEMI .But  , nothing prevents it to evolve as NSTEMI a well . After all , a hyper acute T   MI can  spontaneously lyse in a lucky few , ( Who has that critical  mass of natural  circulating TPA )  .If  these natural lytic forces are only partially successful , it may evolve into de nova NSTEMI.

Bi-phasic T waves in ACS.

A benign looking T waves with terminal negativity in precordial leads  can some times be a deadly marker of critical LAD disease.This has been notorious to cause deaths in young men which often correlates with the widow maker lesion in LAD.

What is a slowly evolving STEMI ?

Prolonged tall T wave phase  possibly   indicate , the myocardium is relatively resistant to hypoxic damage .

The most bizarre aspect in our understanding about ACS pathophysiology  is the concept of  time window , based on which , all our  ACS therapeutics revolve !

Does all myocardial   cells  have a same ischemic shelf  life ?  Can some patients  be  blessed with  resistant myocardial cells   when confronted with hypoxia or ischemia ?

                                 It is well-known  , in some hearts ,  the  muscles go for necrosis within  30 minutes of  ischemia,  while some hearts can not be infarcted even after 24 hours of occlusion .So , slowly evolving STEMI is a feature of  myocardial ischemic resistance .This is not  a new phenomenon as we have extensively studied about the concept   ischemic preconditioning .

We wonder there is something more to it . . .  the quantum of preconditioning  can be inherited .Further  , we are grossly ignorant about  the molecular secrets of  non ischemic metabolic  preconditioning  .

Final message

                         T waves attract less  attention in STEMI . Cardiologists are often tuned to look only the ST segment , after all ,  ACS  itself is classified based on  the behavior of this segment.(STEMI/NSTEMI) . We need to recognise ,there is a significant subset of ACS   affecting exclusively T waves.  Shall we call T elevation  MI ? ( TEMI )

Do not ignore T waves in STEMI. It has more hidden electrophysiological  treasures that  is waiting to be explored .

Read Full Post »

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.

Read Full Post »

Bio-chemical diagnosis of cardiac injury or infarction is  well  documented modality for many decades. Now , acute coronary  syndrome is diagnosed  by a battery of tests  that  detects the  proteins leaking from the  injured  myocardium.

Nephrologists have long been aiming for  such a  marker for ischemic  renal injury  (Not withstanding the fact , they are already blessed with two age-old molecules  creatinine and BUN !)

Neutrophil gelatinase associated Lipocalin (NGAL)

  • This is 25 Dalton molecule  richly secreted within renal  cortical cells in response to ischemic injury .
  • It is released without  modification in the  urine  .High urinary levels  of NGAL  reflect  acute renal  injury.
  • Early experience shows it  is a  promising  investigation and could  become a regular biochemical test in the near future.
  • Urine level of  NGAL >250 ng/ml , 2 hours   after cardiac surgery  predicts impending renal failure  in the next 24-48 hours .The advantage is , it NGAL raises well before serum creatinine.

NGAL After cardiac surgery

http://cjasn.asnjournals.org/cgi/content/full/3/3/665

Lipocalin following PCI

Bachorzewska-Gajewska H et al. Neutrophil-gelatinase-associated lipocalin and renal function after percutaneous coronary interventions. Am J Nephrol 2006; 26: 287-292.

www.ngal.com

References for  NGAL

http://www.ngal.com/literature/popular_reviews_of_the_nature_of_ngal_with_a_focus_on_acute_renal_injury

Final message

  • Cardiologists  and cardiac surgeons  have started  performing  complex    PCIs and  CABGs in  patients with   delicately  and precariously balanced renal function.
  • While ,  cardiologists   challenge  the kidneys with high  osmolar contrast agents ,  the surgeons stress it with extra corporeal circulation.  Many of these patients also  have co- morbid conditions .
  • Often , the cardiac outcome is directly linked to pre /post procedural  renal function .Nephrologists usually  arrive  late  into the filed (Creatinine SOS calls !).By this time the full-blown ATN sets in many.

Now , we have a tool to identify impending ARF , it gives us  little more time and  flexibility in managing the issue .

Read Full Post »

This article is in response to the prevalent belief  about  primary PCI for STEMI   endorsed by world cardiology forums. (Caution: A highly personalized version)

Time window in STEMI

  • Is the window half-opened  or half closed ?
  • Is it open at all ?
  • Or ,does it open only for primary PCI  ,and tend to close down  bluntly for thrombolysis

Modern medicine   grew faster than our thoughts .We have witnessed the audacity of advising  arm-chair treatment  for MI  till later half of   last century . Now we are talking about  air dropping of patients   over the  cath lab  roofs  for primary PCI.

Still ,we have not conquered the STEMI. While ,  we have learnt to “defy  deathin many patients  with cardiogenic shock , we continue to lose patients(“Invite death “)  in  some innocuous forms  of ACS due to procedural  complications  and inappropriate ( rather ignorant !) case selection.

Note : The ignorance  is not in   individual physician mind ,   it is prevalent in the whole cardiology knowledge pool.

The  crux of the issue for modern medicine is ,  how to reduce risk  in patients who are at  high risk and how not to convert a low risk patient into a high risk patient by the frightening medical gadgets.

In other  words ,  arm chair treatment for STEMI was  not (Still it is not !) a dustbin management . It has a potential to save  70 lives  out of 100. What many would  consider it as  ,  nothing but  the natural history of MI .

Medical management of STEMI is ridiculous !

That’s what a section of  cardiologists try to project by distorting the already flawed evidence base in cardiology. Some think it is equal  to no treatment. Here we fail to realise, even doing none has potential to save 70 lifes out of 100 in STEMI who reach the hospital.

Out of the  remaining , 10 lives   are saved by aspirin heparin (ISIS 2) and the concept of coronary  care . Another  7  lives are saved by thrombolysis (GUSTO,GISSI) . PCI  is shown to save saves one more life (PAMI).The remaining 6-7 % will die in CCU  irrespective of what we do .

Of course , now medical management has vastly improved since those days  .  A  thrombolysed ,  heparinsed ,  aspirinised ,  stanised  with adequately antagonized   adrenergic ,  angiotensin system   and   a proper coronary care ( That takes care electrical  short-circuiting  of heart)   will score  over interventional approach in vast majority of STEMI patients.

Now comes the real challenge . . .

When those 70 patients who are likely to survive  , “even a arm-chair treatment“, and the 20 other patients  who will  do a wonderful recovery with CCU care ,  enter  the cath lab  some times in wee hours of morning  . . .what happens  ?

What are the chances  of   a patient  who would otherwise be saved by an arm-chair treatment be  killed by vagaries of  cath lab  violence  ?(With due apologies ,statistics reveal  for every competent cath-lab   there are at least  10  incompetent  ones  world over !)

In the parlance of criminology , a hard core criminal may escape from  legal or illegal shoot out  but an innocent should  not die in cross fire , similarly ,  a cardiogenic shock patient with recurrent  VF  is  afford to lose his  life , but it is  a major medical crime to  lose a simple branch vessel  STEMI (PDA,OM,RCA )  to die in the cath lab,  whom in all probability  would have survived  the arm chair treatment.

Why this pessimistic view against primary PCI  ?

Yes, because  it  has potential to save  many lives  !

Time and again ,  we have  witnessed  lose of   many lifes  in many  popular hospitals in  India ,  where a   low risk MI  was  immediately  converted  to a high risk MI  after an primary  PCI with number of complications .

I strongly believe I have saved 100s of patients  with  low risk MIs by not  doing  for primary  PCI in the last  two decades.

*The argument that PCI confers better LV function and longterm  beneficial effect is also not very convincing for low risk MIs .This will be addressed separately

The demise of comparative efficacy research.

Primary PCI is superior to thrombolysis  : It is agreed , it may be  fact in academic sense .

Experience has taught us , academics rarely succeeds in the bed side.

“superiority studies can never be equated  with comparable efficacy”

Only the  questions remain . . .

  • Where  is comparative efficacy  studies in STEMI ?(Read NEJM article )
  • Why we have not developed a risk based model  when formulating guidelines for   primary PCI ?
  • Is primary PCI for a PDA /D1/OM infarct worth same as PCI for left main ?
  • Is high volume center guarantee  best outcomes ?

Who is preventing comparative efficacy studies ?

Primary PCI : Still  struggling !

This study from the archives  of internal medicine tells   us , we are still scratching  the tips  of  iceberg (Iceberg  ? or Is it something else ?)  of  primary  PCI

Even a  pessimistic approach can be  more scientific  than a optimistic  !

When WHO can be influenzed and make a pseudo emergency pandemic  and pharma companies  make a quick 10 billion bucks  ,  Realise how easy  it is  for the   smaller ,  mainstream cardiology literature  to be  hijacked and contaminated .

Final message

Why we reverently follow the time window for thrombolysis,  while  we rarely apply it for PCI ?   This is  triumph of glamor over truth . The open artery hypothesis remains   in a  hypothetical state with no solid proof  for over 2o years since it was proposed.

Apply your mind in every  patient , do a conscious decision  to either thrombolyse  ,  PCI or none . All the three are  equally powerful approaches in tackling a STEMI , depending upon the time they present .Remember , the third modality of therapy comes free of cost !

Never think ,   just because  some one  has  an access to a sophisticated cath lab 24/7   , has a iberty to overlook the  concept of time window  !

Remember  you can’t  resuscitate   dead myocytes , however advanced your enthusiasm and   interventions are !

Realise , common sense is the most uncommon sense in this hyped up human infested planet.

Read Full Post »

Once in a while the ACC/AHA comes with knock out articles. Here is a  must read  topic for every cardiologist.

How to diagnose MI in ECG ? Sounds , insulting ?

After reading this you should change the way 12 lead  ECG is looked at . . .

Experts from the article

  • How to make the best of lead AVR  ?  Just invert it and you get a + 30 degree lead which  was hither  to unavailable .A new window of opportunity to diagnose   antero lateral MI .
  • Shuffling  the 12 leads to a have an anatomically contiguous  ECG
  • Know , how to label STEMI  with a  .5mm ST elevation  (Minimal STEMI ?)

And lot more exciting  tips  !

If you  think ,  all these are new stuff in cardiology you are grossly mistaken .These concepts are more than 10 years old (In Sweden it is 25 years old ! )

When  European heart journal published  the article   “Myocardial Infarction redefined ”  in year 2000 many missed out the importance . For those who missed it (just  10 short  years have gone by )    ,  Let us update ourself  at least  in 2010 !

Thanks to ACC and JACC.

Click on the link

For PDF article click on the Image

Read Full Post »

Human body is  now  approached by many of the physicians as  collection of  multiple  organs . This is  the price we pay for modernity in medical science. The era  of great physicians  in general medicine has gone . Now, a  super specialist  of one organ  is  rarely concerned about what is happening to the patient’s  other organ ,  it is  considered    foreign to him  ! While ,  this is the dominant thinking pattern of   modern-day specialist

Let us  travel intime  and  go to the year 1954 . . .

Three  physicians from Michigan ,USA  published  one of greatest observation in clinical sciences , namely the ECG changes in various forms of stroke .

Now , a shrewd physician  , will  suspect a subarachnoid hemorrhage (SAH) by looking at the ECG when the clinical situation demands . But , what we need is every one should develop that skill . We have seen errors happening  even in big institutions (or is it because it is big ?)  when  an elderly person comes with deep T  inversions with or without  altered sensorium being rushed into  CCUs  & cath labs instead of  neurology units.

We  need to teach  our junior  colleagues  . . .  That ,  ECGs of patients with  acute neurological syndromes  (ANS)  can mimic as acute coronary syndromes (ACS) ( especially in elderly ) .

The following ECG changes * are observed during stroke

  • Deep  T wave inversion –   Sub arachnoid hemorrhage
  • Cerebral thrombosis   –      Prolonged QT interval, U WAVES
  • Cerebral hemorrhage –      ST segment  shifts /T inversion

 

The ECG changes tend to occur very early after CNS injury.May last up to 1 week. They are not useful to identify the type of stroke. But , deep T wave inversions strongly suggest SAH rather than ICH or thrombotic stroke.

What is the mechanism of these ECG changes ? 

It is a clear proof that heart and brain are interconnected by neural network. All the noted changes occur during myocardial repolarisation . (ie ST segment )  The current thinking is  (Ofcourse , it is same as our thinking  in 1950s !)  it is mediated by adreneergic surge  initiated by CNS insult  transmitted to  myocardium by the sympathetic system.

Why should SAH produce more  ECG changes than others ?

It is possible the net adrenegic drive from the brainstem and spinal cord will be greater in SAH as it  spreads the entire CNS  through the cerbro spinal fluid. While localised ICH and infarct is  likely to generate less adrenergic impulse. 

Reference

Read the link to circulation 1964 .With courtesey to circualtionaha.com

http://circ.ahajournals.org/cgi/reprint/9/5/719.pdf

This came 50  years  ago , we still quote their work and no one has improved their work . 

Final message

If  only  we make the  clinical bed side teaching as a  regualr habit ,  we  do  justice to   our  great  physicians of the past ,   who enriched  our  life  with their  clinical  skills  and  passion for knowledge  sharing .

Read Full Post »

Myocardial infarction (STEMI)  occurs in two distinct arterial  territories .The anterior LAD circulation and postero- inferior RCA/LCX circulation.The incidence is equally shared.

There has been some  learned and unlearned perceptions about Inferior MI.

Inferior MI is less dangerous than anterior MI.  True or false ?

Answer: Essentially true in most situations.

Reasons.

Inferior wall of the heart (strictly speaking there is no walls for heart , only surfaces , which blends with adjacent areas)  inferior wall  is formed by diaphragmatic surface and posterior surface.Inferior MI can occur by either RCA or LCX obstruction.The outcome of inferior MI is determined by mainly by  the extent  of   LV myocardial   damage it inflicts.To  quantitate this  we need to know , how much of LV is supplied by RCA , or LCX or combination of both ? This depend on the coronary dominance .It is estimated , the bulk of the LV is supplied ( up to 75%  ) by LCA. This becomes further high in left dominant circulations . In fact , it is believed LV can never get involved in non dominant RCA occlusions. This has brought in a new terminology  called “Small inferior MI”.Inferior STEMI due to PDA  occlusion or in a co -dominant circulation is not yet studied

Apart from the above  anatomical considerations the following clinical observations  have  been made regarding inferior MI.

  • When thrombolysis was introduced , many studies  suggested the the ST elevation in inferior  leads toched the isolectric levels  in most situations even without thrombolysis.Technically, this implies spontaneous , successful thrombolysis are more common in RCA. Among the thrombolysed ,persistent ST elvation is a rare phenomenon.
  • The well known difference in the conduction defect between anterior and inferior MI  is an important contibutor for better outcome in the later.(AV blocks in inferior MI , are often transient, non progressive, supra hisian location rarely require permanent pacemakers)
  • During acute phase cardiogenic shock occurs in a minority (That too , only if RV shock is included )
  • Even in the follow up the ejection fraction in inferior MI is  almost always above  40%. In many EF is not affected at all.
  • Progressive adverse remodelling of LV is rare

When can Inferior MI be dangerous ?

Anatomical factors

Inspite of the  above  factors  inferior MI can not be taken lightly . Especially when it  extend into posterior, lateral , (Rarely anterior) segments.

While  posterior extension  is often  tolerated , lateral extension is very poorly tolerated .This is probably explained as  the extension involves the vital free wall of LV and the laplace forces could precipitate LVF. Free wall rupture is also common in this situation.

Posterior extension , predominantly involves the surface of RV which is less important hemodynamically. Of course incidence of MR  due to it’s effect on posterior mitral leaflet can be trouble some.

inferior MI ECG

High risk clinical catagories.

Out of hospital STEMI  are at  equal  risk irrespective of the territories involved  .This is because,  primary VF does not differentiate , whether  ischemia comes from RCA or LAD .

  1. In elderly , dibetics and co existing medical condtions  the the established  benign   character  of  inferior MI disappear, as  any  muscle loss  in LV has equally adverse outcome.
  2. Even though  inferior MIs are immune  to cardiogenic shock  , a equally worrisome  prolonged hypotension due to high vagal tone, bradycardia, plus or minus RVMI can create trouble. Fortunately , they respond better to  treatment. Except a few with extensive transmural RVMI outcome is good.
  3. Presence of  mechanical complications of  ventricular septal rupture , ischemic MR can bring  the mortality on par with large anterior MI.

How different is the clinical outcome of infero-posterior  MI with reference  to the  site of  coronary arterial  obstruction   ?

The sequence of  outcome  From  best to worse  : Non dominant RCA* → Dominant RCA but distal to RV branch → LCX dominant with large OMs

* It is believed   an  acute proximal  obstruction of a  non dominant RCA may not be mechanically significant, but can be electrically significant as it retains the risk of primary VF and SA nodal ischemia. The ECG changes  can be very minimal or  some times simple bradycardia is the only clue. One should be able to recognise this entity (Non dominant  RCA STEMI)  as the outcome is  excellent and these patients  would never require procedure like primary  PCI

** A inferior MI due to a dominant LCX and a large OMs have comparable outcome as that of extensive anterior MI. The ECG will reveal ST elevation in both inferior and lateral leads.

***In patients with prior CAD  and collateral dependent  multivessel disease  the  inferior anterior sub classification does not make much sense as  entire coronary circulation can be mutually interdependent.

Final message

Inferior STEMI  generally lacks the vigor  to cause extensive damage to myocardium in most situations .Further they respond better to treatment. Risk stratification of STEMI based on the location of MI has not been popular among mainstream cardiologists. This issue needs some introspection as  the costly and complex treatment modalities like primary PCI  is unwarranted in most of the low risk inferior MIs.

Related posts in my blog:

1.Why thrombolysis is more effective in RCA?

Read Full Post »

Older Posts »