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Cardiac Output (Stroke Volume)


Cardiac output is defined as the amount of blood the heart pumps throughout the circulatory system per minute. It is the product of stroke volume and heart rate. 

Stroke volume is the volume of blood pumped out by the left ventricle of the heart during each systolic cardiac contraction. It is calculated by deducting the end-systolic volume from the end-diastolic volume. It is controlled by “mechanical events” and are hence heavily regulated by inotropic influences (changes in the body that alter the force or energy of the heart's muscular contraction). 


Digoxin is a type of positive inotrope which increases the amount of calcium in myocytes (calcium stimulates the heart to contract). It may be given to patients who have had a recent heart attack, or to those whose hearts have been weakened after heart surgery.


Beta-blockers, calcium channel blockers, and anti-arrhythmic medicines are negative inotropes which help the heart pump less blood per heart beat. This slows the nerve impulses that travel through the heart. Consequently, the heart does not have to work as hard because it needs less blood and oxygen.


Sources:

https://www.deltexmedical.com/decision_tree/stroke-volume-and-cardiac-output/#:~:text=Stroke%20Volume%20(SV)%20is%20the,end%20systolic%20volume%20(ESV).

https://www.ncbi.nlm.nih.gov/books/NBK547686/

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