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What is dfference between successful thrombolysis and successful reperfusion in STEMI ?

Posted May 27 2009 10:51pm

Thrombolytic therapy ,  has been  the specific treatment  for STEMI for  many decades. Primary PCI*  is  shown to be  superior  than  thrombolysis  if   performed   early  by an experienced  team in a dedicated facility. (*Conditions apply). It is estimated ,   currently only a  a fraction  STEMI  population get primary PCI (<5%) in ideal conditions . Another fraction , get  primary PCI by inexperienced cardiologists  in low volume centres.

So , thrombolysis   remains, and  would continue to remain ,   the    primary  mode of therapy for STEMI  in the  present and near  future !

How do you assess the successful  thrombolysis ?

It should be recognised ,  there is a fundametal flaw in this  question !

The aim of thrombolytic therapy is  not  to   lyse  the thrombus  , but also  to restore the coronary blood flow to the  myocardium – also called reperfusion . One may wonder , why the term ,  thrombolysis  should ‘t be  used interchangeably with reperfusion. 

A successful thrombolysis  never guarantees  a good reperfusion , for the simple reason ,  distal blood flow in an  obstructed coronary artery  is dependent on ,  many factors  other than relief of obstruction.

Apart from the potency of drug,     other   important factors  that determine  successful  lysis &  reperfusion are  . . .

  • Timing of opening of artery , if the thrombolysis is delayed  ,  the distal myocardium is dead , and   it won’t allow blood flow to enter the mycardium.
  • Microvascular integrity is as vital as epicardial vessels.
  • Distal microvascualture  plugging by the thrombotic debri . This is called”no reflow “

So , we should  primarily assess myocardial reperfusion rather than epicardial thrombolyis ! following thrombolysis .

What are the parameters available to assess successful reperfusion /thrombolyis?

  1. Clinical : Relief from chest  pain. Angina relief  , though subjective is an indication for adequate reperfusion of ischemic myocardium.
  2. ECG-ST segment regression > 50%
  3. Cardiac enzymes: Early flushing of  intra myocytic CPK into systemic circulation and hence early peaking of CPK MB (<1ohours instead of 24h)
  4. Reperfusion arrhythmias(AIVR-Less specific) .Primary VF is now thought to be reperfusion related.
  5. Infract related artery(IRA) patency by coronary angiogram
  6. Distal TIMI flow/ myocardial blush score/ TIMI frame count

ECG ST regression,  is a direct indicator  myocardial reperfusion   as the ST segment shifts  towards baseline ,  implies  of infarct current of injury . ST regression almost always correlate with good  recovery of LV function  in STEMI .

IRA patency, is an epicardial index , it  does not give information about myocardial blood flow . But ,  a good  distal TIMI flow generally indicates good reperfusion.This  again ,  is  not a fool proof  index,  as even many of the TIMI 3 flow patients  have severely damaged myocardium by echocardiography .

Final message

For the above reasons, one should always  make a distinction between successful lysis and successful reperfusion . Surprisingly ,  ECG  is  the gold standard for assessing successful reperfusion of myocardium ,  while CAG tell us  about epicardial patency and possibly reperfusion also.

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