Posts Tagged ‘sub maximal stress test’

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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Sustaining a STEMI  may be a  pathological  end  point  for  coronary  artery disease. But ,  from the  management point of view it is  actually  a starting point for CAD evaluation  .Strategies to prevent further   cardiac  events   must be formulated .

How do you manage a asymptomatic  un-complicated  post  STEMI   patient*  at discharge ?

  1. Do a sub- maximal symptom limited EST and then discharge.
  2. Advised  to come back after 2 months for a  stress test or Perfusion imaging
  3. Continue  with intensive  medical management without EST or  CAG and monitor only the symptoms
  4. Advice coronary angiogram   in all and decide depending upon the lesions (Pre -discharge CAG )
  5. I am a modern day cardiologist  . This question does not arise . . .  as I do only primary angioplasty for all my cases !

( *Please note ,  this forms the bulk of  STEMI population (up to 60 %  )

Answer : Your guess is the correct answer!

Why we need to risk stratify STEMI at discharge ?

The  morality and outcome in STEMI  though appears  to be a   continuously falling  curve ,  the slope is not linear.

The classical   mortality till discharge is about 6-8  %. Between discharge and 3oth day there is 1-2 % additional mortality

At end of first year there is  further   2 % mortality. From  second year onwards there is an annual attrition rate up to 3 %.

The aim of doing  a pre-discharge  EST is to do identify  ” patient  subset ” who are destined to die  within 30 days of STEMI.  If you schedule the   EST  after 6-8  weeks  one can not prevent these two deaths out of 100 !

( Of course ,  we assume   a prompt revascularisation in those vulnerable would prevent this !).  By doing so , we can avoid the bulk of unnecessary PCIs  that  happen  with  routine CAG following STEMI.

Pre discharge EST can be done safely  within 5-7 days  with  a symptom  limited test (70 % of  THR or up to HR of  120 /mt ) This  simple test if it is negative can virtually R/O  a  critical proximal  lesion with near 100% sensitivity.

Should we  risk stratify patients  who have undergone pPCI as well ?

Most of us  would love to believe ,   once  pPCI is  done to the  patient , he  reaches  a therapeutic end  point. But  it is not the truth . It is  the degree of  LV dysfunction ,  extent of contrary coronary lesion  ,   co existing risk   factors  and  the  intensity of medical treatment  only  would  determine the long term outcome.

It is very important to  realise  the pPCI is aimed at opening the IRA  and other lesions are  often left alone. So never  believe  pPCI   per se  would confer total risk reduction following a STEMI  .  There is considerable evidence to suggest  the opposite may be true at least in high high risk pPCI  ,where  metals are   placed  in  complex ,   vulnerable thrombotic milieu.  Hence it  seems logical  to risk  stratify  all patients   after primary PCI   (In fact, this population require  more vigilance )  .

When will you advice an  EST following  pPCI ?

It is usually not needed in the immediate discharge phase in single vessel disease which  would have been  tackled during pPCI.In multi-vessel CAD , where  only the IRA was tackled during pPCI  ,the same guidelines that of  thromolysed  STEMI shall apply  .Since we know the coronary anatomy already ,  EST helps us to evaluate the hemodynamic status of non IRA lesions if  there are any  . While ,  this is a  logical debate , logics has a rare place in medicine . It is ironical ,  stress test   is rarely  done  even after 6months following pPCI  in most centers.

Final message

It is  a  pity  ,  anatomical risk stratification  has squarely beaten  the scheme of   physiological risk stratification in most cardiology centers . A pre -discharge EST* was a  good concept that gave us an idea about the coronary reserve  after the ACS.  It was a collective wisdom of cardiologists  that has hanged this useful concept.  It is still more shocking ,  to note even the  scheduled  6 week   EST is  dropped from the  post MI work up in some  institutions.

* Many would consider  ordering an early EST in STEMI is an act of bravery ! The fear seems to be genuine   and most will agree with that.  But , please remember a physiological test  (Cheapest and simple is EST or a  Nuclear perfusion )  should precede  CAG  in all  asymptomatic  post STEMI  population  whenever possible . If  EST could not be done  prior to CAG for some reason   , at least do it following the CAG . It  will have  an  important impact  on the downstream decision making  which is often an  inappropriate  PCI  !

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