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Difference b/w early vs. late changes in cardiac muscle:

a. incresed number of myocytes and sustained EF vs. decreased EF
b. decreased HR and sustained EF vs. increased HR decreased EF
c. increase sarcomeres per myocyte and sustained EF vs. relpacement with fetal proteins and decreased EF
d. incresed O2 demand vs. decreased 02 demand


I go with B.




increased O2 demand and decreased O2 demand


that makes an idiot. more work early to maintain CO, until failure.


Could you just explain that q?- early or late chage in cardiac muscle-what is that in reference to eg. kids versing adults, early and late Histologic M.I. changes, early and late gross M.I. changes, early and late chages of a cardiac cycle-please explain.[usmle will be Very specific and concise with those qs.]???


I think it means this:

early change=concentric hypertrophy; effective frank-starling law, and an increase in cardiac contractility, due to the heart trying to maintain CO, in the face of some stressor (increased afterload, etc).

late change=dilational hypertrophy; frank-starling law no longer effective, and a decrease in the ability of the heart to maintain CO.

O2 demand correlates with cardiac work. More work is actually being done in the early stage of CHF than in the late stage.

AM I close?


Almost... answer is C , increase in sarcomeres per myocyte is the defenition of hypertrophy, thats the early adoptation of the heart muscle as it is trying to compensate for increased load. Later though, instead if adult proteins, fetal variant are starting to be expressed, those are much stiffer, and elasticity of the heart goes up and contractility goes down.This is where ACE inf are working, theya are somehow interfere with expression of fetal proteins thus prolonging survival with CHF.
Hope it helps.


I would like to see a source on is the first time I have heard it. Thanks.


Id like to see a reference for that q also,not necessarily BRS. :?:


I wish I had the books with me. If I ll remember the author, I ll let you guys know. I have everything in my notes, with which I verify facts, but no refferences to authors, sorry. It might have come through my professors.


as far as question goes: 1. Thats hyperplasia, which does not occur in card muscle.
2. The earliest response is increased HR, not decreased.
4. O2 demand increases in both early and late CHF.

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