Posts Tagged ‘ischemic cardiogenic shock’

We know human heart contracts and relaxes in an active manner .Systole happens when calcium is pumped from the cytoplasm into the actin myosin complex and diastole occur when the calcium is  returnded back into the sarcoplasmic reticulam .The rate of calcium reuptake  is detemined by the  molecules calmodulin ,  phospholamban and it’s functional status .

When the heart fails acutely , as in asystolic cardiac arrest , does it fail in systole or diastole ?

The seemingly simple question can never be answered dogmatically.

Pathological studies of post moretm specimens suggest contraction band necrosis is a feature of systolic cardiac arrest .We are not yet sure  yet . . . How a heart will appear when it stops in diastole .In fact , if a heart gets struck in systole it means systole has actually  occured  and  because it fails to relax  it  assumes a  stone like contracture  state .

While  the  molecular basis  are pretty much confusing  , what is clear is we do get number of clinical situations where a acute diastolic dysfunction may occur.

Flash pulmonary edema

The mechanism in the former could be sudden afterload mediated mechanical stunning while in the later ischemia mediated acute contractile and diastolic dysfunction.

In both situations there is severe pulmonary venous HT and class 4 pulmonary edema. The credance to concept  of acute diastolic dysfunction came to light , when  we noticed many of  these patient with acute LVF had preserved EF %   and absence of MR to explain acute pulmonary edema .

*Coronary vasospasm–induced acute diastolic dysfunction in a patient with Raynaud’s phenomenon http://www.springerlink.com/content/g1774g34544q2482/

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Apart from  acute  coronary syndrome,    cardiac  failure is   the most common clinical  presentation of  CAD. Cardiac failure ,  classically present with dyspnea on rest or on exertion , while angina is the dominant presentation in ACS.  

What if  ,  both these  occur together in an acute fashion ?

Yesif it occurs  together it is called ischemic cardiac failure . Fortunately , this is quiet uncommon . It has   an adverse outcome,  especially if it occurs  as a companion of NSTEMI . Let us see how . . .(  Most of the episodes of cardiac failure  in CAD  means only  LV failure )

For cardiac failure to occur , there need to be a mechanical contractile dysfunction or defect . In CAD population , this can  occur in  one of the following way.

  • Loss of LV muscle (Acute  Myocardial infarction as in STEMI)
  • Mechanical defects (Mitral regurgitation/VSR etc)
  • An arrhythmia (Commonly VT or AF / CHB )  can precipitate  cardiac failure

Apart from these three , there is  an important mechanism of acute LVF, namely ischemic stunning of major part of LV resulting in severe mechanical dysfucntion.This is a dangerous form of cardiac failure (Pathologivcclaly it is thought to represent  contraction  band necrosis !) this occurs in global ischemic situations manifested as gross global ST depression.

So,  there are two types of  ischemic LVF  .  STEMI   occuring due to infarct( ± ischemia ) Other  one (NSTEMI)entirely due to ischemia.

Logically ,  one  may n’t   refer  STEMI related LVF as  ischemic LVF at all  , as infarct has already occured. While , NSTEMI related LV could be the ” True ischemic LVF “

What are the differences between cardiac failure that occur in  STEMI and NSTEMI ?

lvf in nstemi stemi

Is post infarct failure  ( The commonly used terminology  , now out of vogue ! )  a type of ischemic LVF ?

In the strict sense , it is not . Here the dead myocardium , is responsible  for the   failure .To label a  LVF , as  ischemic , ongoing ischemia must  be  documented and further it  should  be shown to  contribute   for the  mechanical dysfunction .

This is of vital importance ,   if you wrongly attribute ischemia  as a cause for  the LVF , the patient may be taken up for emergency  revascularisation .It is not going to help much (Infact , it may  worsen !) as  this cardiac failure is not going to be corrected  .What we require ,  here is an  aggressive medical management  protocol .

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