Archive for the ‘Blood pressure’ Category

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)



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