Stroke Volume and Epinephrine

[erythrocyte666]

---

Members do not see this ad.

Does epinephrine increase/decrease/not affect the stroke volume?

 

[amy_k]

Ephinephrine increases the contractile force in cardiac muscle which increases stroke volume.

 

[erythrocyte666]

Ephinephrine increases the contractile force in cardiac muscle which increases stroke volume.

I thought when epinephrine increases the heart's contractile force, it decreases the end systolic volume.
But epinephrine also increases heart rate, which decreases end diastolic volume (since ventricles do not get enough time to completely fill with blood).
And since stroke volume is the difference between the end diastolic and systolic volumes, I was leaning towards the no change in stroke volume.
Can you please clarify?

 

[Cawolf]

Sympathetic stimulation will initially increase the cardiac output by increased contractile force.

The decreased filling does not become evident until a much higher, unsustainable heart rate (or a sustained tachycardia for an extended period).

This is why dysrythmias such as SVT are dangerous, there is not enough filling time and the overall CO decreases to a subphysiological value.

So you are right, but the ionotropic effects are much more appreciable than the chronotropic effects - unless it goes on for too long, or the rate gets too high.