Cardiac output depends on which factors?

• A. Stroke Volume and Heart Rate
• B. Heart Rate alone
• C. Stroke Volume alone
• D. Systemic vascular resistance

Answer: (A)

Cardiac output is determined by how fast the heart beats and how much blood is pumped with each beat. In other words, CO equals heart rate times stroke volume (CO = HR × SV). Heart rate is the number of beats per minute, while stroke volume is the amount of blood ejected with each beat. If either increases while the other stays the same, the overall output rises, and both can rise together to meet the body's needs.

Systemic vascular resistance relates to afterload—the pressure the heart must work against to eject blood. It can influence how much blood is ejected per beat, but it is not a direct determinant of cardiac output itself. The primary factors that define CO are heart rate and stroke volume, making the combination of those two the best answer.