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#1
07-27-2016
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Q.Explanation for conditions that inc & dec pulse pressure?

Q. Why pulse pressure increases in hyperthyroidism, aoric regurgitation,arteriosclerosis, obstructive sleep apnea, aoric stiffening and in exericse?Can anybody explain how pulse pressure increases in each of these conditions?
Also, what is the reason for decreased Pulse pressure in aortic stenosis?

#2
08-08-2016
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hyperthyroidism, aoric regurgitation,arteriosclerosis, obstructive sleep apnea, aoric stiffening and in exericse

Hi there,

Blood pressure =cardiac output x vessel resistance.
Poiseuille's equation for resistance is R=8Lη/πr^4. (L: length, η:viscosity,r:radius)
Cardiac output= stroke volume x heart rate.
For BP to increase, either cardiac output or vessel resistance has to increase.
In arteriosclerosis, the affected arteries' radius reduces, leading to increased resistance to blood flow and thus increased BP. Aortic stiffening is another word for arteriosclerosis.
In hyperthyroidism, aortic valve regurgitation and during exercise, you get increased cardiac output and thus BP. During exercise, muscles need more blood; both heart rate and stroke volume increase. Hyperthyroidism is a case of hyperdynamic circulation: increased metabolic rate leads to increased heat production and peripheral vasodilation, which your body counteracts by increasing cardiac output. Hyperdynamic circulation is established in cases of aortic valve regurgitation, too: during ventricular diastole, blood flows back into the left ventricle, through the abnormally open aortic valve, which leads to increased end-diastolic volume and thus increased stroke volume and cardiac output.

In severe aortic valve stenosis, when the opening is not big enough, stroke volume decreases and thus BP decreases as well (this can lead to syncope, particularly during exercise when more blood flow is needed).

Hope this helps.
 The above post was thanked by: Sam imkeyim (08-12-2016)
#3
08-10-2016
 USMLE Forums Newbie Steps History: Not yet Posts: 2 Threads: 0 Thanked 0 Times in 0 Posts Reputation: 10

Quote:
 Originally Posted by Chloe_WH hyperthyroidism, aoric regurgitation,arteriosclerosis, obstructive sleep apnea, aoric stiffening and in exericse Hi there, Blood pressure =cardiac output x vessel resistance. Poiseuille's equation for resistance is R=8Lη/πr^4. (L: length, η:viscosity,r:radius) Cardiac output= stroke volume x heart rate. For BP to increase, either cardiac output or vessel resistance has to increase. In arteriosclerosis, the affected arteries' radius reduces, leading to increased resistance to blood flow and thus increased BP. Aortic stiffening is another word for arteriosclerosis. In hyperthyroidism, aortic valve regurgitation and during exercise, you get increased cardiac output and thus BP. During exercise, muscles need more blood; both heart rate and stroke volume increase. Hyperthyroidism is a case of hyperdynamic circulation: increased metabolic rate leads to increased heat production and peripheral vasodilation, which your body counteracts by increasing cardiac output. Hyperdynamic circulation is established in cases of aortic valve regurgitation, too: during ventricular diastole, blood flows back into the left ventricle, through the abnormally open aortic valve, which leads to increased end-diastolic volume and thus increased stroke volume and cardiac output. In severe aortic valve stenosis, when the opening is not big enough, stroke volume decreases and thus BP decreases as well (this can lead to syncope, particularly during exercise when more blood flow is needed). Hope this helps.
Superb explanation! I was so confused with this! Thanks a ton

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