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Posts Tagged ‘coronary risk factor’

Is hypertension really a major risk factor for CAD ?

    1. Yes it is !
    2. No . . . it is not !
    3. May be !
    4. I don’t think so !

Ans : Any of the above can be a  right response , depending upon our basal and perceived  level of knowledge .

Answer analysis

  1. SHT  is  one of the risk factor for CAD  agreed ,  but definitely not a major one , as SHT per-se rarely precipitate a STEMI
  2. Unless SHT occurs with dyslipidemia, smoking or diabetes it is  rare to cause ACS.
  3. The only  adverse effect of SHT  is  , it has a potential  to aggravate atherosclerosis  by promoting epithelial injury and dysfunction.
  4. Hypertension is a well known  major risk factor for cerebro vascular disease while it is minor risk factor for CAD !
  5. We do not know yet why cerebral vessels are intolerant to high blood pressure while coronaries are pretty happy  with it !

Final comment

SHT is not a major risk factor  for CAD ! At worst , it can propagate chronic CAD. This sort of reasoning  may be considered a huge controversy  . . .but it is really not !

  • One evidence for the above observation is  , we  have  been struggling hard  for over a half a century  to prove a elusive  point that controlling blood pressure  to optimal levels  would  dramatically reduce  cardiac   events !
  • Further,HT’s  relationship with acute coronary syndrome especially STEMI  is vague , it is very rare for patients with accelerated hypertension or malignant hypertension to  present with STEMI *

* Caution :Young doctors should not get confused with this seemingly  controversial observation .This write-up , tries  to convey  a point  , SHT may not be that bad for coronary arteries when compared to cerebral arteries . However BP control remains  vital in  all patients who have  developed a cardiac  event or in patients with multiple risk factors .

Please note ** SHT is still  a powerful risk factor for cardiac failure.(Acute LVF to be precise ) ***SHT can aggravate unstable angina , but very  rare to precipitate unstable angina.**** SHT ./High intra-coronary  pressure can theoretically  dissect or fissure a plaque . (The fact that , HT is so prevalent in a community  but spontaneous  coronary  dissections are not !  should make us think further !)

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It is well-known sexual arousal and activity is a powerful hemodynamic stress .In the healthy persons it is never an issue .In fact there is data to suggest sexually active men and women live longer.

But , in patients with cardiac risk factors or an established coronary event unrestricted  sex can be a risk factor for CAD.

There needs to be a distinction  between a coronary risk factor and a coronary  trigger .Trigger is an  immediate switch  for a coronary event in a  patient with  baseline risk profile .It is highly unlikely triggers alone can  cause an ACS .There need to be risky substrate.

Extra marital sex could be such a trigger in some .(Both male and female)

  • The sexual activity performed with guilt  has  more powerful risk.
  • First time offenders
  • New  partners
  • New environment

All of the above are  supposed to increase  the risk .

The mechanism  attributable is  a   sudden adrenergic  surge  which inappropriately high when compared to marital sex . In conservative societies , the effort taken to hide the illicit relationship   is much more stressful than the event itself. And hence these men and women carry on their new-found coronary risk for longer periods.

Reference

http://www.ncbi.nlm.nih.gov/pubmed/20382352

http://drwes.blogspot.com/2010/04/extramarital-affairs-and-heart.html

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                                     Hypertension is considered a major cardiovascular risk factor.Hypertension  can have multiple physiological and pathological effects on heart . The common response to  raised arterial pressure is the hypertrophy of the left ventricle ( LVH). This can increase the risk of heart failure in few ( Mainly diastolic failure)  It is a leading cause for stroke  and   less often a  coronary event.

What links Hypertension and  coronary artery disease

                                           Coronary artery disease is almost synonymous with atherosclerosis. There is no separate entity called hypertensive coronary artery disease. But HT can accelerate the process of atherosclerosis. It is widely understood, hypertension can cause  physical endothelial damage and functional impairment of endothelial function.The physical damage ie enothelial disruption , or erosion is a very uncommon phenomenon . So currently  there is sufficient clinical experience  HT is considered dangerous for coronary artery only if it is with the  company of diabetes and hyperlipidemia. (This will seem controversial as it is against the findings of iconic Framingham trial!)

What the medical community refers to hypertension , may not be really so inside  for the coronary arteries.

                                             The relationship between brachial cuff blood pressure and the intra coronary pressure has very little linear relationship. So one should recognise it is the intra coronary hypertension that has a immediate impact on the coronary events. Now only , we are beginning to understand the complexities  of the relationship between HT and CAD. If we analyse a series of individuals HT per se is not a very serious risk factor for CAD* , but it is a number one risk factor for stroke. 

Why HT in isolation  often result in stroke , rather than a MI ?

While HT  is notoriously common to result  intracerebral hemorrhage, the same HT  would not cause  intramyocardial bleeds . Why ?

What is protecting the myocardium against this complication ?

                                      The exact mechanism  is not clear.Acute surges of blood pressure can increase the risk of stroke many times  but  rarely precipitate  a coronary event(  But may cause a LVF) . The reasons could be the coronary endothelial shearing stress is less than the cerebral blood vessels.Both cerebral and coronary circulation has  auto regulatory mechanism . The coronary auto regulation is more robust in that it does not allow  intra coronary pressures to reach critical levels .There is no clinically relevant intra myocardial hemorrhage reported  even during malignant hypertension.

*But a  high intra coronary pressure can sometimes  result in spontaneous coronary dissection and plaque fissure .Lipid mediated injury is vey much facilitated in a high pressure environment.

Has Controlling blood pressure  to optimal levels  , reduced the overall CAD morbidity and mortality ?

                    The answer is yes, ( But not an emphatic yes ! ) Some studies had been equivocal. It is very difficult to say , how much benefit is attributable to BP reduction  per se  and   how much is attributable to indirect effect on atherosclerosis prevention.

Hypertension during ACS

                            High blood pressure during an episode of unstable angina or STEMI can increase the myocardial oxygen demand and worsen the ischemia. It requires optimal control with nitroglycerine ( Preferably ) or beta blocker and ACE inhibitors.Even though HT is commonly associated  with ACS,  one can not be sure the ACS is preciptated by HT. Many times the sympathetic surge during an ACS keeps the blood pressure high.It is a common experience the blood pressure suddenly dropping to normal or hypotensive levels once the pain and anxiety is controlled.

Hypertension during thrombolysis

                           High blood pressure is a relative contraindication for thrombolysis.It need to be emphasised here, It is the  the fear of stroke that make  it contraindicated .The heart can tolerate  thrombolytic agents delivered at high BP .In fact logically ,  hemodynamically and also  practically it is obseved , thrombolytic agents administered at relatively high blood pressure (140-160 systolic) has better thrombolysis than a patient who is lysed at 100mmhg.

                       The coronary pressure head which contain the thrombolytic agent (streptokinase and others ) need to have pressure jet effect on the thrombus.So the  mean coronary perfusion pressure becomes  a critical determinant of success of thrombolysis.

                            It is a paradox of sorts , very high blood pressures are a relative contraindication for thrombolysis and at the same time normal pressure patients fare less well to thrombolysis.

 Final  message

                        Hypertension continues to be a major cardiovascular risk factor.It has direct and indirect effects on the heart.Generally HT is more of a risk factor for stroke than CAD.A slightly high BP ( Just around the  upper limits of normal or just above it ) has a hemodynamic advantage during thrombolysis.(Class C evidence )

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