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antidepressant
Everything is possible  Topics: 66 Posts: 2103 |
ACE inhibitor, reduce the vasoconstrictive effect of angiotensin II and thus decrease afterload.(Goljan) i thought vasodilation will cause incrase blood flow to heart, then how does it reduce afterload? anyone can explain?
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digant
| Forum Newbie  Topics: 7 Posts: 32
ace inhibitors act on both arteries and veins. so by acting on veins(vasodilation)---> it decrease preload(blood flow to heart).. and by acting on arteries, it decrease afterload... so simple....
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antidepressant
| Everything is possible Topics: 66 Posts: 2103
digant thank, but Goljan said , ace inhibitor decrease the vasoconstirctive action of peripheral resistant arterole, and thus decrease afterload, how is that possible, because if there is vasodilation, more blood is supposed to go to the heart, right? if more blood goes to heart, how is afterload reduced?
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NNL
| Awaitin The Unexpected  Topics: 779 Posts: 6613
the preload is the degree to which the myocardium is stretched before it contracts and the afterload is the resistance against which blood is expelled. By dilating the arterioles and arteries the force required to pump the blood from the heart into the aorta is called after load, is greatly reduced and hence causing less work for the heart. Dilation of arteries and veins results in a bit of pooling effect
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antidepressant
| Everything is possible Topics: 66 Posts: 2103
thanks nnl, thanks for clearing this.it totally makes sense,. got it now, about afterload, veins have pooling effect, but arteries dont, right?
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antidepressant
| Everything is possible Topics: 66 Posts: 2103
Another Quiery, want to make sure, i got it right: about HTN In hypertensive patients, they have too much Na in their body, which increases water in ECF, increases plasma volume, increases SV, heart has to work again extra volume, leads to HTN. also, Na goes in smooth muscle of peripheral resistant arteriole, Na opens channel for Calicum, increased Ca in smooth muscle of arteriole, vasoconsctriction, increased TPR( TPR= viscosity/r4), increased TPR keeps more blood in arteriole during diastole when heart is filling up with blood, increased diastolic pressure. (goljan) the quiery is in my underlined part, does it mean, there is not enough blood to pump, so, heart try to pump out all the blood it has, increased SV and increased BP?
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antidepressant
| Everything is possible Topics: 66 Posts: 2103
thanks macintosh, but doesnt it mean if you vasodilate the peripheral resistant arteriole, you decrease TPR, more blood returns to heart ( as in septic shock, high output failure)?
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antidepressant
| Everything is possible Topics: 66 Posts: 2103
antidepressant wrote: if you vasodilate the peripheral resistant arteriole, you decrease TPR, more blood returns to heart thanks, macintosh, i understand afterload and preload( as for now), so there is no confusion about Goljan, is there?
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blacko
| Forum Newbie Topics: 0 Posts: 4
a sample way to see it is to consider after load as the peripheric resistance (the resistance against the cardiac ejection) and preload as the end diastolic volume.
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antidepressant
| Everything is possible Topics: 66 Posts: 2103
thank you, 
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