Sea_gull
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Please revise CVS physiology in step I ,you will get the answer.
GL
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| study_ing
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remeber the systolic pressure is more dependant on Cardiac output, whilst diastolic pressure --> systemic vascular resistence.
usually what happens is that for a given stroke volume, the elastic arteries expand during systole to 'accomodate' it whilst in diastole, this stored blood is 'released' ..this helps maintain diastolic pressure and reduces systolic ones.
in PDA, the low pressure pulmonary circuit is linked to systemic circuit. during diastole blood wud rapidly empty out into this system.
thus DBP is low.
y the high SBP? well the heart has to increase its cardiac output to meet systemic demands as a significant amount is now shunted via the pda.
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| study_ing
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well, while we r on the topic, just wanted to mention one additional point..
with old age, elastic arteries become more rigid. hence sbps are higher.
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| som
Forum Guru
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gud expln. and DOC for isolated sysolic HTN is thiazides
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| tolito
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thanks study_ing. same principle goes for AV fistulas.
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| nadiabarati
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thanks a lot study-ing. you are a great teacher.
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| nadiabarati
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actually I thought during systole there would be a fall in pressure because of shunting blood into pulmonary circulation...so increased pulse pressure!!
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| nadiabarati
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sorrry I meant decreased pulse pressure.
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| study_ing
Forum Fanatic
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well that cud be a possibility. however remember aortic regurg is a similar situation.
low resistence outflow= lowers systole
High output of heart=systole higher
the final systolic pressure wud depend on the net effect i guess.
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