Cardiac output depends on heart rate and which other factor?

Cardiac output depends on heart rate and which other factor?

• A. Stroke volume
• B. End-diastolic volume
• C. Left atrial pressure
• D. Pulmonary artery pressure

Answer: (A)

Cardiac output is determined by two factors: how often the heart beats and how much blood is pumped with each beat. The amount pumped per beat is stroke volume, so the factor besides heart rate that sets cardiac output is stroke volume. Stroke volume itself depends on preload (captured by end-diastolic volume), contractility, and afterload. End-diastolic volume reflects preload and can influence stroke volume through the Frank-Starling mechanism, but the direct multiplier in the cardiac output equation is stroke volume. Left atrial pressure and pulmonary artery pressure relate to filling and afterload but are not the direct determinant in the CR equation. So the best answer is stroke volume.

Cardiac output is determined by two factors: how often the heart beats and how much blood is pumped with each beat. The amount pumped per beat is stroke volume, so the factor besides heart rate that sets cardiac output is stroke volume. Stroke volume itself depends on preload (captured by end-diastolic volume), contractility, and afterload. End-diastolic volume reflects preload and can influence stroke volume through the Frank-Starling mechanism, but the direct multiplier in the cardiac output equation is stroke volume. Left atrial pressure and pulmonary artery pressure relate to filling and afterload but are not the direct determinant in the CR equation. So the best answer is stroke volume.