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Hello world
I want to ask something about Guyton's curves
I'm confused about the right atrial pressure in these curves
In the steady state, cardiac output and venous return are, by definition, equal at the point of intersection. Why then do the cardiac and vascular function curves go in opposite directions and why do they have opposite relationships with right atrial pressure?
The answers lie in the way the two curves are determined. The cardiac function curve is determined as follows: as right atrial pressure and end-diastolic volume are increased, there is increased ventricular fiber length, which leads to increased stroke volume and cardiac output. The higher the right atrial pressure, the higher the cardiac outputthis is the Frank-Starling relationship for the heart.
The vascular function curve is determined as follows: as right atrial pressure is decreased, venous return increases because of the greater pressure gradient driving blood flow back to the heart. The lower the right atrial pressure, the higher the venous return.
so what is the right atrial pressure at which the two curves intersect?is it the right atrial pressure before bringing venous return in the venous return curve or right atrial pressure after bringing venous return and increasing the CVP and EDV in the cardiac function curve?
for a steady state:
1-venous return must equal cardiac output
2-right atrial pressure for the heart to bring its venous return equals that of right atrium to pump its output
I don't understand the second condition
I hope my question is clear sorry for posting this before in allopathic but I get better responses here
thanks in advance
I want to ask something about Guyton's curves
I'm confused about the right atrial pressure in these curves
In the steady state, cardiac output and venous return are, by definition, equal at the point of intersection. Why then do the cardiac and vascular function curves go in opposite directions and why do they have opposite relationships with right atrial pressure?
The answers lie in the way the two curves are determined. The cardiac function curve is determined as follows: as right atrial pressure and end-diastolic volume are increased, there is increased ventricular fiber length, which leads to increased stroke volume and cardiac output. The higher the right atrial pressure, the higher the cardiac outputthis is the Frank-Starling relationship for the heart.
The vascular function curve is determined as follows: as right atrial pressure is decreased, venous return increases because of the greater pressure gradient driving blood flow back to the heart. The lower the right atrial pressure, the higher the venous return.
so what is the right atrial pressure at which the two curves intersect?is it the right atrial pressure before bringing venous return in the venous return curve or right atrial pressure after bringing venous return and increasing the CVP and EDV in the cardiac function curve?
for a steady state:
1-venous return must equal cardiac output
2-right atrial pressure for the heart to bring its venous return equals that of right atrium to pump its output
I don't understand the second condition
I hope my question is clear sorry for posting this before in allopathic but I get better responses here
thanks in advance
