Cardiac output equation

Cardiac output equation

• A. CO = HR x SV
• B. CO = SV / HR
• C. CO = EDV - ESV
• D. CO = preload x afterload

Answer: (A)

Cardiac output is the volume of blood the heart pumps per minute, and it is determined by how fast the heart beats and how much blood is ejected with each beat. The correct relation multiplies heart rate by stroke volume: CO = HR × SV. For example, at 70 beats per minute with a stroke volume of about 70 mL per beat, CO ≈ 70 × 70 mL/min = 4,900 mL/min (about 4.9 L/min). The other expressions don’t describe how flow is generated: SV divided by HR isn’t a measure of flow, EDV minus ESV gives stroke volume, and preload and afterload influence stroke volume but do not directly multiply to yield cardiac output.

Cardiac output is the volume of blood the heart pumps per minute, and it is determined by how fast the heart beats and how much blood is ejected with each beat. The correct relation multiplies heart rate by stroke volume: CO = HR × SV. For example, at 70 beats per minute with a stroke volume of about 70 mL per beat, CO ≈ 70 × 70 mL/min = 4,900 mL/min (about 4.9 L/min). The other expressions don’t describe how flow is generated: SV divided by HR isn’t a measure of flow, EDV minus ESV gives stroke volume, and preload and afterload influence stroke volume but do not directly multiply to yield cardiac output.