Posts Tagged ‘pulmonary edema’

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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Humans have roughly 5 to 6 liters of blood at any given time in their  body  . Out of  this*

50% (2500ml)  is located in the systemic venous compartment.
18% is within the pulmonary circulation participating in the vital oxygenation
12% (500-600ml) is within the cardiac chambers.
8%  is in the arterial tree of  the body.
5%  is  within the  capillaries.
2%  is in the aorta.
* Source : Best & Taylor Physiological basis of  medical practice 1966, 8th edition

What is the implication of this predominantly venous distribution of blood  at rest ?

  • A competent venous tone is essential  for the human beings to maintain the erect posture.
  • Bulk of the cause of syncope in humans is due to peripheral  mechanism like loss of vascular tone and resultant venous pooling.
  • The  concept of venous reservoir is so important in emergency situations like  hypotension  as  simple elevation of legs  is equivalent to  infusing 500 -800 ml of intravenous saline .
  • Similarly during acute left ventricular failure trunk elevation and legs dangling down can reduce the pulmonary congestion very significantly and reduce pulmonary capillary wedge pressure (LVEDP)

 Autonomic dysfunction and venous insufficiency

 Autonomic dysfunction and resultant  orthostatic hypotension is directly related  to venous reservoir dysfunction.Increasing effective circulatory volume by elastic stockings or administration of mineralocorticosteroids like fludrocortisone (.5mg/day ) can be useful in this condition

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