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Archive for August, 2012

That’s how  one of   the patient  presented  to our hospital .  An echo documented  severe aortic stenosis with a  peak aortic gradient of 80mmhg  and  a  bounding  systolic blood pressure of  180 mmhg . Is that an exception ?

I recall the early days of medical school when  we are fervently   taught  that  systolic  blood pressure is primarily determined by stroke volume and LV contractility .

The above example clearly proves this  is  explicitly wrong  .

Now , we understand  systolic blood pressure have many determinants   . Stroke volume is  just one of them .

The tone  , distensibility  of major blood vessels arising from aorta determine how a pressure wave is going to get amplified .

If you  say stroke volume is not  major determinate of systolic blood pressure   . . . .  does it  imply ,   the antique  bed side cardiac sign  Pulsus parvus  et- tardus  a myth ?

No ,  it still holds good . But it is not a hard sign .  We realise now , a patient with a well felt carotid can have a severe Aortic stenosis .

  • Pre- existing systemic hypertension is a  valid explanation.
  • The other popular explanation for  loss of systolic decapitation due to associated  aortic  regurgitation   may be  acceptable . (Not really proven though ! )

What will be the central aortic  pressure  in critical Aortic stenosis ?

It is definitely lower than brachial cuff pressure .This will explain the systolic blood pressure is actually an amplified signal .

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Rescue PCI rescues

  1. Myocardium
  2. Patient’s life
  3. Both
  4. None
  5. Cardiologist pride

Answer:

All of the above can be a correct response in varying situations.

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Which is  the most important factor that determines thrombolysis failure in STEMI  ?

  1. Thrombus load .
  2. Drug efficiency
  3. Time delay
  4. Presence of a mechanical lesion
  5. Hemodynamic instability

Answer : 3 .(Though all 5 factors operate )

Failed thrmbolysis occur in about 40-50% after streptokinase and slightly less with TPA   and TNK-TPA . Delayed arrival and late thrombolysis are  most common cause of failed thrombolysis. As the time flies , the  myocardium gets damaged and the intra coronary  thrombus gets organised .Both these processes make delayed thrombolysis a futile exercise.

               Not all STEMI patients have large thrombus burden. There need to be a critical load of thrombus for thrombolytic to be effective

Some may have a major mechanical lesion in the form of plaque fissure, prolapse and it simply blocks the coronary artery mechanically like a boulder on the road  . The poor  streptokinse  or the rich Tenekteplace !  nothing can move this boulder .The only option here is emergency PCI .

How will you know when the patient  arrives in ER with STEMI whether his/ her coronary artery is blocked with soft thrombus or hard mechanical boulder ?

It is impossible to know.That’s why primary PCI has a huge advantage.  But still thrombolysis is useful as some amount of thrombus will be there in all patients with STEMI.Lysing this will provide at least a  trickle of  blood flow that will jeep the myocardium viable and enable us to take for early PCI.

Final message

The commonest cause for thrombolytic failure is the time of administration and the degree of underlying mechanical lesion  . So  it does not make sense  to blame  streptokinase always !

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The right to left shunt  in TOF  occurs by  which of the the following route ?

  1. RV- VSD- LV -Aorta

  2. RV-  Aorta

  3. RV – VSD- Aorta

  4. All of the above can occur

    Answer : 2   Most shunting occur by direct streaming of RV blood into Aorta . If the aortic  override  is near 50 %  it need not even cross the VSD in it’s  circuit. (Although theoretically all of the above can occur)

     

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The last rites for routine   Swan Ganz catheterisation ( In STEMI ) was  performed  by a  land mark JAMA article  in 1996 .

Now . . .  is the turn for intra aortic balloon counter pulsation (IABP) .

A conceptually attractive concept  was laid to rest in Munich ,West Germany , this week at annual  European society of cardiology ,  Scientific Sessions  .August 2012 .

What a crash for a great  hemo-dynamic  principle    in acute MI which ruled the roost for over three  decades !
Just Imagine ,   how many man hours , millions of  worth of consumables  wasted  . . .  better  not to talk about  associated   aortic injuries .

This is what we call   premature evidence based harm”

I  wonder  . . .  whether  I am  justified in making this extreme comment .

Please read for yourself  , this early online release alert  from  NEJM .

http://www.nejm.org/doi/pdf/10.1056/NEJMoa1208410

Reference

Connors A, Speroff T, Dawson N, Thomas C, Harrell FE Jr, Wagner D, etal. The effectiveness of right heart catheterization in the initial care of critically ill patients. JAMA 1996;276:  889-97.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2352214/pdf/bmj00561-0005.pdf

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The principles of pre-discharge EST  

This concept came about 20 years ago (1980s) to risk stratify patients following  ACS to triage early coronary angiogram and revascualrisation. Generally patients are discharged by 5-7 days after an MI  (May be  3-5 days in some hospitals)  . Doing an exercise stress test  early within  2 weeks has not been very popular with many cardiologist even though it was recommended by many guidelines.The type of stress recommended  here  , is heart rate limited sub maximal 70% of  THR (Usually around  140 /mt )  is performed . This is due fear of precipitation another ACS.

Still,  there are definite  advantages for  pre-discharge EST .It help us  identify  high risk  subsets of  STEMI and reduce the  intermediate term mortality .More importantly it  gives  us an opportunity  to  exclude  inappropriate  revascualriations  even without an angiogram . (The well known coronary dogma  ie  if a post STEMI patient performs > 10  METS ,  his  heart carries little  risk  for  future events  still holds good  !)

With the advent of liberal usage of CAG and improved techniques of revascularistion ,  most  patients  directly undergo pre-discharge CAG rather than EST !

Further reading

Does any cardiologist have guts to do a pre- discharge EST after  a successful primary PCI ?

Read a related article in this blog .

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An awkward  argument for routine EST following primary PCI

Please remember,  primary PCI is not the end of the management of STEMI. Primary PCI is an IRA focused intervention. We need to study other lesions and their the flow pattern as well. Logically we need to do a test for adequacy of  baseline vascularity and the current revascularisation . Simple deployment of  a stent in IRA (without documentation of good flow during exertion ) is not acceptable to believers of  scientific medicine  . Resting TIMI 3 flow conveys no meaning for a patient who is going to be ambulant and active. A stress test will come in handy .

The micro-vascular integrity and resistance following an extensive STEMI is best studied by the adequacy of exercise induced  coronary hyperemia (This is physiologically equivalent to the much fancied FFR in cath lab ) . One can consider EST following a primary PCI as an non invasive substitute for the collective FFR of all three vessels including the IRA that is stented .

Does any cardiologist have guts to do a pre- discharge EST after a successful primary PCI ?

Typical responses would be

  • Why the hell I should do it ?
  • Do you know how risky it is to do a EST early after a primary PCI ?
  • If at all I have any doubt , I would prefer a non invasive PET or Thallium to study the adequacy of revascularisation.

If you think , it is too risky to exert a successfully revascularised patient early after a STEMI . . .   at the same time   argue  to do it in non revascularised patient routinely .  Do we not see a huge irony here ?

Other inference could be . . . we are still suspecting the quality of our revascularisation during PCI !

If  EST is contraindicated after a primary PCI , are we going to advice  these patients against indulging in any activity requiring moderate exertion fearing a stent occlusion ?

. . . What a way to interpret the aftermath  of a   ‘state of the art ‘ procedure called primary PCI !

In science ,  correctness is more important than politeness !

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