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Posts Tagged ‘coronary risk factors’

What is a coronary risk factor ?

Right from the days of  Framingham study we have conferred a privileged   place   to  few  cardiac  risk factors.

they are

  • Diabetes mellites
  • Hypertension
  • Hyperlipidemia
  • Smoking
  • Obesity

They are referred to as conventional risk factors .  What is the convention ?  Do they deserve  the  cult  status they enjoy ?

Today we also have a  cluster  of non conventional risk factors like , Lip (a) , low HDL, Homocystenemia , CRP , Apo B etc . Currently ,  in any large cohort of CAD  up to 30 %  do not exhibit even a single conventional risk factor  . This is a huge number .Hence   we tend to give more importance to genetic make up and mental stress etc  .The search is still  on for newer risk factors .

Why some research  findings are difficult to comprehend ?

It is because we are yet to  decode the  intricacies  of  human biology  fully . Our knowledge is so superficial  , as we chase  a pseudo scientific  proofs   for  a  presumed  hypothesis.  The classical example is the concept called good cholesterol (HDL) and reverse cholesterol transport which  is never based on solid scientific foundations.

Take the sorry story of  Torcetrapib

Many consider  low HDL  as an independent CAD risk factor to be a  myth  or else why should we miserably fail  to have any positive effect of  increasing the HDL  levels by pharmacological means . (One argument is physiological  and natural elevation of  HDL  would still be beneficial  . But the issue is still wrapped in a statistical mystery

This  paper from  JAMA   adds further insight into our ignorance about  the  genesis of CAD .

The data is from  NRMI registry.

The statistics  reveal  a stunning fact .In  the overall CAD cohort ,  patients  with no major risk factors  experience  highest mortality and the ones with maximum   risk factors have least mortality ! What a shocker of a study ?

http://jama.ama-assn.org/content/306/19/2120

This  paper  would bring  jitters to the population ,  but in the real sense it sends an important message .

A significant population develop CAD without any  known risk factors.(14.5% in NRMI registry )

If a person develops  a CAD without any major risk factor  ,  it seems  . . . it is not at all a  good news   !  rather we need to introspect , why  without any risk factor he or she has suffered CAD ,

One inference is  their vascular system is more vulnerable ! Some hidden factors are operating . How to manage such  patients  without any target to intervene ?   A diabetic dyslipidemic smoker has a   definite  therapeutic target  .

What about these   lesser  humans  who   develop   CAD without any known risk factors  ? They  tend to suffer more !

Is  CAD  due to DM/SHT  is better than  others  ? This study seems to say so ” Known devils are better than unknown ones ”

Final message

Unlearning is an   “essential and fundamental”  component of   scientific learning .  In this progressive scientific world , this applies  most to   medical profession  than any other field !

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We know diabetes, smoking, hyperlidemia, hypertension are major risk factors for progressive vascular disease. They damage the vascular endothelium either directly or indirectly ,   by aggravating the atheroscelortic process .  Diabetes apart from affecting the medium sized arteries , also affect the microvasculature.  Smoking  has a direct effect on endothelial function .It depletes vascular nitric oxide. High levels of circulating lipids injures the sub endothelial structures and invades the media by entering macrophages .So , all these 4 risk factors either operate independently or interact with each other and result in progressive vascular    disease.

While we  believe  , these risk factors do not have any bias in attacking the human vascular  tree, in the real world it is observed they have their own  behavior pattern and  have unique predilection and a deadly alliance .

For example , in  chronic smokers TAO is the commonest manifestation , thrombo angitis is far too less common to occur in the coronary arteries.

Similarly  hypertension  per se  rarely results in an acute coronary syndrome while it is  the  single  important  cause for cerebro vascular  disease. Diabetes especially in women has very strong predilection for CAD , while diabetic per se is a lesser risk for stroke. Hyperlipedimia may be the one which has fairly even risk throughout the vasculature. Similarly there is  a difference in renal and   carotid arterial involvement with reference to  the conventional  risk factors .

SHT diabetes dyslipidemia coroanry risk factor

Why this apparent difference ?

We are unlikely  to get an answer to this question in the near future .  Left to the youngsters  . . . of tomorrow !

* Note of  clarification

The source for the above chart is collected from various studies and also a huge observational data from our hospital. There could be some geographical variation , a given individual may respond differently to these risk factor depending upon his genetic predisposition and susceptibility . So the above data can be applied to general population and not to a individual.

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