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Posts Tagged ‘blood pressure’

What happens to diastolic blood pressure in severe Aortic stenosis ?

Traditional answer: The diastolic BP remain unchanged. Only systolic BP falls as it is related to LV  stroke volume .(What we refer to as systolic decapitation of BP  )

Reasoning :Diastolic BP is related to peripheral vascular resistance , hence aortic stenosis has  little impact on diastolic BP .

 Further analysis

If we assume only the systolic blood pressure  is bound to decrease in  AS , at one  critical point of time*  systolic BP  should  approach  the diastolic pressure and pulse pressure should approach zero .This can not happen , hence at that point  diastolic pressure will also fall.

*What is that  point ?

No one really knows !

Correct answer

In severe aortic stenosis  both systolic and diastolic pressure falls , but the fall in systolic BP is more striking .

* Though it is customary for clinicians  to discuss them in isolation both systolic and diastolic  blood pressure are closely coupled parameters..In the absence of peripheral run off one of the  strong determinant of diastolic BP  is . . .  systolic BP !

Complex concepts

1. What happens in combined aortic stenosis and regurgitation ?

In  combined AS and AR   we get  pulsus bisferiens. implying  AR will  elevate the systolic blood pressure in spite of obstruction.

2.What happens in associated systemic Hypertension  and aortic stenosis . (Which is very common combo in elderly )

Since HT will increase the  aortic pressure , the LV-Aorta gradient tend to fall.

However ,this  does not happen always as if the original cause for HT was  dependent  more on the stroke volume rather than peripheral mechanisms .

3. Aortic stenosis with aortic  atherosclerosis .

A stiff aorta augments the percussion wave amplifying the symbolic BP and blunting the  classical anacrotic pulse of AS.

4.What happens to BP  during exercise in  severe AS ?

Exercise demands raise in systolic BP and temporary reduction in diastolic BP due to peripheral  vaso dilatation in exercising muscles.

If a fixed  crtical AS does not allow the systolic BP to raise  as required , diastolic continue to fall pulse pressure should still become wide .

Excercise testing is a tricky business in AS. Some have attempted it to assess the functional capacity.(Read below)

Reference

 

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                    circulatory                                                                            A normally  functioning  circulatory system is vital for our survival . We have about 6000 ml of  blood, circulating  all over the  body in an  approximate time of 15-20 seconds.The pressure at which this blood moves across the body is called the blood pressure . Hypertension  or simply , high blood pressure is an undesirable  hemodynamic disturbance  in human circulatory system.Systemic hypertension is the most common type of hypertension. The blood pressure is primarily  dependent  on the status of the blood vessel(vascular resistance)  and cardiac contractility. This regulation is under  many neural and hormonal factors.Further  the blood pressure varies depending  upon the blood vessel calibre, and the local milieu.There is a progressive drop in blood pressure from major arteries to the small arteries .The pressure drop is maximum  across the arterioles to reach the venules .The venous circulation has the lowest pressure, it ends up at right atrium with a mean pressure of 0- 5mmhg.

Importance of regional variation of blood pressure.

It should be realised  ,  each organ has it’s own regulated blood pressure.The brain  perfuses by the  intracerebral pressure .The lungs decide how much should be the pulmonary arterial pressure.The kidney not only controls it’s own pressure but also  has a major regulatory role in  systemic pressure by rennin angiotensin system.The examples are numerous, portal system has it’s unique pressure controlling hepatic hemodynamics. The  retinal blood vessels regulate  intra ocular pressure. While the human  circulatory system has a wide variation of blood pressure  across the breadth and length of vascular system,  it is ironical a single snap shot BP with a brachial cuff is used  to define the normality and if it is normal every thing is thought to be  hunky dory !

 

 

It is widely acknowledged now , aging of humanity  is nothing but aging of our vascular system

                                    So we should have new parameters to assess individual organ’s vascular health as well as the currently popular systemic vascular health.The single important factor that determine coronary endothelial damage is the intra coronary pressure.It is never taken into account in any of the cardivascular mortality studies. This is the prime reason for  the widely prevalent conflict in the cardiology literature , namely : Controlling systemic  blood pressure has poor correlation with  cardiovascular outcome. Many of the so called normotensive individuals  have serious hemodynamic injury in their  coronary arteries.This was made apparent in the  ASCOT LLA  study , in which patients with  near normal blood pressure also benefited from statin therapy , implying  endothelial damage could occur at any level of systemic blood pressure.

What is the normal intracoronary pressure  ? When do you diagnose intracoonary hypertension?

The normal intracoronary pressure is around 40mmhg . Intra coronary hypertension as a clinical entity  is yet to be  recognised . There is no defintion available for intracoronary HT  , intracerebral hypertension as well. 

It’s still a  long way to  go , for the cardiology and neurology  community to assess non invasively  intracoronary pressures and  intra cerebral arterial pressure to prevent  coronary events ant strokes.

Final message

Simple risk prediction using brachial cuff blood pressure is a grossly unscientific method (Sorry, i really mean it ) to assess one’s vascular health.There has been  few attempts like vascular endothelial health assessment by fore arm blood  flow , central aortic pressure (Instead of brachial cuff pressure) as an  index for risk predictment and  assessment for hypertension is suggested.

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