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Learning from the “Dead” and “Dying” : Coronary care unit secrets !

Posted Feb 14 2010 9:37am

STEMI is the commonest cardiac emergency . Many believe we  are close to  conquering  it .  It is hardly the truth .

  • The  mortality is  up to  30 % out of hospital and another 6-8  % within CCU  and another 2 %   at  30 days due to recurrent ACS   .This  is followed by an   annual attrition rate OF 25  due to progressive LV failure  .
  • The commonest mode of death is electrical,  ie primary VF.
  • Mechanical deaths are also equally important. Free wall rupture carries 100% mortality . Ischemic MRVentricular  septal rupture (VSR ) may also result in deaths.

Here is a case history and ECG of a  patient with STEMI .

After thrombolysis the paradox happened . ST elevation  increased by 4mm and soon the patient became restless with worsening pain and became silent instantaneously ,  with monitor showing EMD and asystole .A diagnosis of free wall rupture was made.

What we used refer  in our CCU (Madras medical college Chennai .One of the oldest CCU in  South Asia )

as   “Action pontentialisation”  of surface ECG . This ECG finding has  great  clinical significance .

Here is a zoomed up view of a qrs complex of  the patient which is very

closely resembles an action potential

Picture courtesey  http://ocw.tufts.edu/Content/50/lecturenotes/634488/634591

Pathological basis of  “Action potenial”  Like ECG

  • When the ST elevation is huge and wide it mimics  an action potential .
  • Myocyte action potentials are normally recorded epicardially in physiology lab where a  micro electrode with glass pipettes directly enter the myocyte.
  • A giant ST elevation and a sustained dome indicate the quantum of  electrical injury is  very large and the  ECG electrodes is picking up the myocyte electrical events like that of a intra cellular electrode.
  • It is to be recognised  ,  ST elevation in chest leads is substantially taller than limb leads   because the exploring electrode  is located just above the myocardium . But,    when a  huge  ST elevation  is recorded  over a limb lead (as in this patient )  one can imagine   how intense the electrical  charge  of  the myocardium  should  have been  !

This heavy downpour of electrical energy that  emanate from the myocardium   means two things

  • The area of infarct is very substantial
  • The tissue in question is  very unstable .

Clinical correlates of  action potential ECG

  1. Damage is transmural the   infarcted area is softfriable and often hemorrhagic .
  2. The pericardium is also  likely to get involved in the injury process .
  3. The myocardium is  rupture prone or already torn .
  4. Even minor hemodynamic stress can be fatal in these patients
  5. An episode of vomitinga fall in blood pressure,   an episode of  LVF or a short run of VT is suffice  to result in a fatality.

The death happens by a sudden rupture ,  EMD and asystole .

Can a life be saved  by the much fancied Emergency PCI  ?

Not really. The PCI  can not reverse the myocardial damage so it’s role is little . But any way it should be done and it will  be done to give the benefit of doubt (Of course the risk of doubt !)

What is the risk  of  PCI in these situation ?

The infarct related artery * if opened up can convert a bland infarct into a  “angry red”  hemorrhagic  infarct .This   is as good as  giving  the patient ,  a  farewell  party for his journey to heaven !

Note : Primary PCI  definitely  saves life in STMI . The  * is applicable only in persistent ST elevation late after an acute MI.

Final message

When the ECG  assumes  a shape of an  action potential ,  it is often a sign of  imminent  death  . Even though it may sound a pessimistic  view  it is often the truth  . Of course an  emrgency PCI or   CABG are  the only options available we have  to be remember the above truth  ,   as we   play  those sophisticated  games  within their coronary arteries.

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