Cardiac Output

Definition

Cardiac output is the volume of blood pumped by the heart per minute, which is a crucial measure of the heart's pumping ability and a key indicator of cardiovascular function. It is the product of heart rate and stroke volume, and it plays a central role in the delivery of oxygenated blood to the body's tissues.

5 Must Know Facts For Your Next Test

1. Cardiac output is calculated as the product of heart rate (beats per minute) and stroke volume (volume of blood pumped per beat).
2. Factors that influence cardiac output include preload (venous return), afterload (resistance to blood flow), and contractility of the heart muscle.
3. Cardiac output is a key determinant of blood pressure and tissue perfusion, as it governs the delivery of oxygenated blood to the body's cells.
4. Abnormal cardiac output, either too high (high-output failure) or too low (low-output failure), can indicate underlying cardiovascular or respiratory problems.
5. During pregnancy, cardiac output increases to support the growing fetus and placenta, reaching a peak during the third trimester.

Review Questions

• Explain how cardiac output is calculated and the factors that influence it.
  • Cardiac output is calculated as the product of heart rate (beats per minute) and stroke volume (volume of blood pumped per beat). The factors that influence cardiac output include preload (the volume of blood returning to the heart), afterload (the resistance to blood flow), and the contractility of the heart muscle. Preload affects the filling of the ventricles, afterload determines the pressure the heart must overcome to eject blood, and contractility influences the heart's ability to generate force and pump blood efficiently.
• Describe the role of cardiac output in the delivery of oxygenated blood to the body's tissues and its importance for overall cardiovascular function.
  • Cardiac output is a critical determinant of blood pressure and tissue perfusion, as it governs the delivery of oxygenated blood to the body's cells. A sufficient cardiac output ensures that the body's tissues receive an adequate supply of oxygen and nutrients to support their metabolic needs. Abnormal cardiac output, either too high (high-output failure) or too low (low-output failure), can indicate underlying cardiovascular or respiratory problems and lead to various health complications. Maintaining a healthy cardiac output is essential for overall cardiovascular function and the body's ability to meet its oxygen and nutrient demands.
• Explain how cardiac output changes during pregnancy and the physiological adaptations that occur to support the growing fetus and placenta.
  • During pregnancy, cardiac output increases to support the growing fetus and placenta. This is achieved through a combination of factors, including an increase in heart rate, stroke volume, and blood volume. The placenta, which acts as the fetus's respiratory and excretory organ, requires a significant amount of blood flow to facilitate the exchange of gases, nutrients, and waste products. To meet this increased demand, the mother's cardiovascular system undergoes various adaptations, such as vasodilation, decreased peripheral resistance, and an increase in blood volume. These changes allow for a greater cardiac output to be delivered to the placenta and other maternal tissues, ensuring the fetus receives the necessary oxygen and nutrients for proper development.

Related terms

Stroke Volume:

The volume of blood pumped from the ventricles with each heartbeat, which is influenced by preload, afterload, and contractility of the heart muscle.

Heart Rate:

The number of times the heart beats per minute, which is regulated by the autonomic nervous system and can be affected by various factors such as physical activity, stress, and age.

Cardiac Cycle:

The sequence of events that occur during a single heartbeat, including ventricular diastole (filling) and systole (contraction), which determine the heart's pumping efficiency.