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Posts Tagged ‘DCM’

This seemingly straight forward question is often asked in cardiology boards.

The answer to this question is  important in the bedside as well ! Ironically ,  with  sophisticated  diagnostic modalities the complexities  has  also multiplied .

The following table attempts to simplify it. ( Mostly written with a personal knowledge and ignorance !)

Please click on the table to visualise a high resolution  image.

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Human heart is a compact elastic organ .  We know elasticity is lost when it is stretched beyond a point.This is what happens in dilated  cardiomyopathy .When the heart muscle fibers stretch  too long from the baseline  it loses its ability to contract and relax   efficiently.In fact  , after a cut of point even if it comes the original length the elastic fibers are fractured and suffer from irreversible damage.

Among  the systolic vs diastolic dimension it is the diastolic dimension that becomes important in defining dilatation.

When do you say a ventricle is dilated?

  1. When the EDD (End diastolic dimension) > 60mm
  2. EDD > 56mm
  3. EDD > 10 % from baseline
  4. EDD > 25 %  from baseline

Any of the above can be right.

The normal human ventricle measures  between 35 to 55mm in diastole .

Currently accepted  definition for enlargement of heart is EDD  of 56 mm and above. Some believe  in a more strict criteria of 60mm.

Consider the following situation

A man with 35mm EDD   can increase 20mm ( ie 60 % )  from of his baseline  and still be  labeled as  normal LV  dimension ! . If the above patient  is  destined to develop dilated cardiomyopathy    his  heart  would  begin  its  final  journey  slowly but   surely ( from 35 mm  ! ) . So ,  according to current criteria  we can diagnose  DCM only after it travels the half way towards hell .   What a way to define DCM  ! Be cautious LV dimensions can fool  you  . . .

If the EF is low and symptoms develop early ,  one may recognise  the above  entity ( at least erroneously !) as non dilated cardiomyopathy or RCM.

If  the patient is relatively asymptomatic and   if we   overlook  the  baseline  LV parameters ,  we are likely  to miss  most of the early  DCMs

Final message

We need to stress the importance of baseline LV dimension in defining DCM  . It is proposed  from this  site ,  an increase of 25 %   and above from baseline  can be   included as an   additional  criteria  for  LV dilatation . This  could  help us understand   the early muscle dynamics in DCM.

Un-Answered questions

  1. How to diagnose  early DCM ?
  2. When does the EF begins to decline in DCM ?
  3. What is the relation between EDD and EF %?
  4. Is HF with preserved LV function ( previously called diastolic dysfunction ) is the earliest point in the natural history of  DCM
  5. Is there a overlap  between non dilated cardiomyopathy , RCM and early phase of DCM ?

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Dilated cardiomyopathy (DCM )  is the commonest  cardiac muscle disease .Diagnosis is simple and straight forward. All that we  require is,   documentation of LV dilatation and contractile dysfunction.The nomenclature of cardiomyopathy has remained a difficult exercise .This   is primarily  due to   iatrogenic  & intellectual confusion  among  cardiologists . They mixed up etiological and morphological entities together ,   later on  they  wanted to de-link  etiology from morphology  ,  ultimately they realised  when illness strikes the heart ,   it   can not differentiate the  morphology, etiology and pathology as we would want to   . So , whenever possible we have to label  cardiomyopathy with all components (Dilated cardiomyopathy due to alcohol with some restrictive features.)

This article  tries to evoke  some thoughts    about  why  LV dilatation  is central to the understanding of cardiomyopathy.

DCM is the prototype where LV dilates with global hypokinesia.The upper limit of   LV diameter is generally considered to be 56mm in diastole.  (Range 35 -56mm) .This cut off  point is too empirical  for the simple reason, the  left ventricle can dilate   up to  50 %  from it’s basal diameter and still technically  be within normal limits.( A 3.5 cm LV ( end diastolic diameter ) can dilate to 5.6 cm ,i e  a 50 % dilatation , still LV  has not reached the upper limit of normal  )

Even as we do not have a clear  answer to the above issue , we  recognise  left ventricle muscle can hypertrophy, progressively  dilate , transiently dilate, fail to  dilate ,  regressively  dilate  or  hypotrophy .These changes can be dynamic and heavily influenced by hemodynamic and local pathologic factors like fibrois, interstitial proliferation etc. Meanwhile , the pharmacological ,   surgical /catheter injuries we  inflict    , modifies  the muscle behavior in a positive or negative manner.

In this back ground ,  we have found a new entity called NDCM .

Apart from  DCM, a newer form of  cardiomyopathy  is being recognized  .This is often referred to as NDCM (Non dilated cardiomyopathy)  .Global  systolic LV dysfunction  with normal  LV dimension.This a similar to the terminology MDCM (Minimally/Mildly  dilated  cardiomyopathy  where LV dimension  do not  increase  beyond   15 %  upper limit of normal  ) .

This is seen in CKD and diabetic individuals.Atria may be enlarged .Diastolic dysfunction may co exist.  It is no surprise,  this entity closely mimics RCM. But in RCM LV systolic function  is not greatly compromised till the  late stages , while NDCM it begins with systolic dysfunction. This is the only difference .There can be overlaps .

MDCM was reported in 1990  . Keren gave a excellent insight about the condition  ,  It is unfortunate it failed to take off as a popular  clinical entity .  Cardiologists are argued to use this term liberally in their clinical practice .

Final message

Cardiology is not  that  simple as one would like to ! The two components of cardiomyopathy ie   LV dilatation and LV dysfunction can be temporally dissociated  one may precede the other. To  complicate the matter further, one of them may not manifest at all !

Few ,  still consider many of the RCMs and NDCM are one and the same entities that present in different time frames in their natural history.

So the simplified  concept  to decode the cardiomyopathy conundrum  could be

  • When both  dilatation and dysfunction occur it is classical DCM
  • When dysfunction  alone occur without dilatation it is NDCM
  • When both dysfunction  and dilatation are less it is RCM*(Relaxyl dysfunction must)
  • When dilatation is mild and dysfunction is severe it  is MDCM

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As the name suggests   dilated cardiomyopathy  would imply  cardiac chambers will dilate , at least some time in the course of the disease .It can be minimal, mild or massive. A new entity called  non dilated cardiomyopathy is also gaining wider acceptance . (That will be dealt seperately )

Logic would suggest , the first chamber to dilate in DCM  should be the left ventricle because it is  facing the direct load of systemic blood. But we also know , whenever  LV is stressed , left atrium comes to it’s assistance .

Left atrium does this    by total self sacrifice ( by all  means!)  increases  it’s  force of contraction, elevating it’s  mean pressure or even increasing it’s rate (AF) .

Like most  other critical questions in cardiology  ,  the factors that determine LV dilatation in DCM ,  is  also poorly understood !

  1. Is it the after load ?
  2. Is it the  muscle mass ? or it’s turgid  or flabbiness ?
  3. Is it the interstitial integrity?
  4. Is it the blood volume ?(LVEDV ,  LV residual volume )

When the issue is complex , it is  usual  to  make the   the unknown  genetic defects  ,  the scapegoat !

As of now the most important determinant of LV dilatation  could be  the behavior of the desmins, the gap junctions and myosins the titins etc

If  the LV of a DCM patient  refuses  or  resists  dilatation what  might happen ? Is it good or bad for the patient ?

Here is a catch .  A  LV  that does not dilate  obviously should be  be good for the patient  is in’t ? Medicine is not that simple.

When   LV  fails to  dilate  it means it has become  too  stiff and rigid    and pass on the  burden to  to LA which  faces the music. And in the process it dilates.This is the reason , we  observe  diastolic dysfunction in vast number of DCM patients.( Currently it is estimated > 75% DCM will have significant diastolic dysfunction )

So , now we can imagine how complex the sequence of hemodynamic stress in DCM that determine the chamber enlargement.( RA, RV  dimension in DCM is a separate issue !)

So now answer this question :  Which chamber dilates first in DCM ?

  1. Left ventricle
  2. Left Atrium
  3. Any of the above
  4. Both of the above dilate simultaneously

The answer must be 3 .

Why  recognising this sequence of  chamber enlargement  in DCM   is important ?

  • It gives us an opportunity to assess the dominant mechanism of LV dysfunction.There are reports , where some  DCMs  have more diastolic dysfunction than systolic dysfunction  .This will have important therapeutic implication.Further , many of the infiltrative   disorders of LV can have features of both DCM & RCM .
  • When a RCM begins to dilate it is usually  a harbinger of terminal heart failure. But,  it need not be always true .  A small restrictive LV  , when  dilates ,   may acquire a  slightly improved diastolic properties , as the  LV becomes more placid . And ,  if it happens the LA size may regress.
  • The role of LV restriction devices like, Acron mesh, Dor procedure, plication  in refractory  DCM is not well defined. All these   modalities actually  adds  a small dose of diastolic dysfunction in these patients who have grossly dilated ventricles. This fact is  very important  , as presence of any preexisting  significant diastolic dysfunction in DCM makes  the role of LV restrictive devices and surgery a big question mark !

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The term cardiomyopathy generally denotes a  progressive disease  in clinical cardiology.There was a time   diagnosis  of dilated cardiomyopathy (DCM )  was synonymous with a  delayed death sentence !  Of course , the situation has vastly improved over the years  with the availability of  new medical , interventional and surgical management. Still ,  there is no denying the  fact  ,  DCM continues to  have a grave outcome  especially when it occurs without any identifiable cause .

While we have  variety of aggressive DCMs , we also  have  patients with relatively benign forms of   dilated and dysfunctional hearts  which recover totally .

This reversible forms of DCM is observed in  the following  situations.

Hypertensive dilated cardiomyopathy . The left ventricle  in  some of the  patients with severe SHT  respond to the stress (Increased  after load) by dilatation rather than hypertrophy. This is especially common after an episode of LVF.  If we do an acute echocardiogram the LV function is severely impaired and the LV may  also be dilated. With good control of BP and fluid management the ventricle promptly return  to it’s baseline dimension. The recovery is complete in many . (The mechansim of LV dysfunction acute severe Hypertension is referred to as Pre-load /After load mismatch) Link to concept of Pre load mismatch .

* Note in the past these entities were not called as  cardiomyopathy .

Peri partum cardiomyopathy.

This is a serious disorder of cardiac muscles that occur during pregnancy  few months before  or few months after delivery  . There is correlation between PIH and this entity. Prognosis varies between very bad to excellent. Very few cardiac entities  have a  natural history like this one disease of women.Most of the pregnant women regain their original cardiac status within  year or so. It should be recalled there is high chances of recurrence in next pregnancy.

Alcoholic cardiomyopathy.

The toxic response to alcohol or the additive cobalt can result in DCM .There is overlap  between holiday heart syndrome and alcoholic DCM , where atrial fibrillation is the major problem. Wet Beri beri is the advamced form of clinical DCM that respond to vitamin B therapy.

Tachycardic cardiomyopathy.

This is also a common entity that occur during persistent sinus tachycardia or AF , thyrotoxicosis.Beta blockers are  of great use here.  Recovery is usual if the primary cause is correctable.

Toxic and drug related  reversible LV dysfunction

Adriamycin cardiomyopathy

Tako -Subot  Cardiomyopathy canbe termed as classic form of reversible  stress cardiomyopathy

Miscellaneous conditions

Diabetes and chronic kidney disorders are known to have a reversible form of cardiomyopathy

Some rare toxins  , scorpion envenomation , selenium deficiency can result in reversible DCM

**Ischemic DCM are partially  correctable in many , still  we don’t include it as cause for reversible DCM

*** Many episodes of acute myocarditis can have transient or short term LV dialtation and  dysfunction.they are classified as myocarditis .But there is little  difference (Except acadmeic . . .)  between chronic myocarditis with LV dysfucntion  and cardiomyopathy.

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How will you refer to a ventricle which is not dilated but still has severe global contractile dysfunction ?

Traditionally cardiomyopathy is classified as

  • Dilated (DCM)
  • Hypertrophic(HCM)
  • Restrictive (RCM)

But there is large group of pateints who do not show any of the above features and still have global hypokinesia  contractile dysfunction. this group has been largely ignored .It could constitute up to 25%of all cardiomyopathy.there can be some overlap between non dialted cardiomyopathy and RCM.

We report our experience here with

non dilated cardiomyopathy click to download PPT

non dilated  cardiomyopathy

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                                    Competence of mitral valve is vital  for proper hemodynamics of  heart .A trivial mitral regurgitation ,is observed in nearly 10-20% of normal population detected by doppler echocardiograpgy .This is other wise clinically insignificant. In fact , it is expected  , the sonographers do not report this,  as it might increase the patient anxiety.

Can a mildly incompetent mitral valve be a hemodynamic advantage ?

Left ventricle , physiologically can have only one exit, namely LVOT and aortic valve.If there is normal  impedance , at this level (LV after load )  it  is refered to as  physiological .In disease states , as in cardiac failure there is raised after load or LV wall stress.this makes the LV struggle to pump blood into aorta.The more the dilatation the more the wall stress (Laplace law). more the wall stress more the after load.

 The  main principle of management of cardiac failure  for decades  has been promoting  LV inotropism .Now we have realised this is fundamentally a wrong concept, (Except in acute heart failure). Hence the main option available now is to reduce the after load , ACEI do that most effectively and proven to improve survival.

What is the effect of  trivial or mild MR on LV after load  ?

It is a hemodynamic fact for MR  to increase LV contractility  and Dp/Dt  due to a relative reduction of after load.

In patients with cardiac failure , even a mild improvement in LV contractility can give a  symptomatic improvement .

 

09tmr1

Can mitral valve act as controlled safety valve allowing only a trivial or mild MR ?

This may be difficult . But it happens naturally in many of our patents in cardiac failure .

Probably , these are same  patients who come under the 20% incidence of physiological  doppler  MR .Other group could  form the  functional MR*

We have found, patients with  DCM  with mild mitral regurgitation tolerate excercise better than patients who have very competent and rigid mitral valve.It is presumed a mitral valve which gives in a little bit , decompresses the LV with a symptomatic benefit.But if the MR , is occurs in an eccentric path or it results in significant volume burden the potential advantage becomes a liability.

Related issues

*Functional mitral regurgitation. Functional MR is said to occur , when patients with cardiac failure, and resultant dilatation of mitral annular ring, and lack of opposition of leaflets

While milder forms of MR are well tolerarted  , when it occurs  acutely ( even if it is mild) ,  it can be dangerous and result in sudden pulmonary edema  .This usually happens in acute MI or infective endocarditis etc.

 Final message

  • Minimal or mild  mitral regurgitation without any significant volume overloding  in some of the patients with dilated cardiomyopathy  could bring  a hemodynamic advantage .
  • So one may not unduly worry about , a mild MR (central jet) in patients with DCM.It could be after all a safety exit for overstrained LV

We will report the results of the ongoing study about the impact of presence /absence    of  mild MR on the 6 minute walk test in patients with dilated cardiomyopathy.

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