Cardiac output varies directly with changes in which two factors?

Cardiac output varies directly with changes in which two factors?

• A. Heart rate and stroke volume
• B. Afterload and preload
• C. End-diastolic volume and contractility
• D. Venous return and afterload

Answer: (A)

Cardiac output is the amount of blood the heart pumps each minute, and it is determined by multiplying heart rate by stroke volume. Heart rate is how many times the heart beats per minute, while stroke volume is how much blood is ejected with each beat. So, if either heart rate or stroke volume increases (assuming the other stays the same), cardiac output goes up. The two factors that directly set this output are heart rate and stroke volume. Other factors like preload, afterload, contractility, and venous return influence stroke volume and thus can change cardiac output, but they do so by altering how much blood is ejected per beat, rather than being the direct two factors that determine the output itself.

Cardiac output is the amount of blood the heart pumps each minute, and it is determined by multiplying heart rate by stroke volume. Heart rate is how many times the heart beats per minute, while stroke volume is how much blood is ejected with each beat. So, if either heart rate or stroke volume increases (assuming the other stays the same), cardiac output goes up. The two factors that directly set this output are heart rate and stroke volume.

Other factors like preload, afterload, contractility, and venous return influence stroke volume and thus can change cardiac output, but they do so by altering how much blood is ejected per beat, rather than being the direct two factors that determine the output itself.