Certified Emergency Nurse (CEN) Practice Test

How is afterload defined?

1. The pressure required to fill the heart

2. The pressure the heart must eject against

3. The volume of blood the heart pumps per minute

4. The rate of heart contraction

The correct answer is: The pressure the heart must eject against

Afterload refers to the pressure that the heart must overcome to eject blood from the ventricles during systole. This concept is crucial in understanding cardiac physiology and the hemodynamics of heart function. When the ventricle contracts, it creates pressure within the chamber, and this pressure must surpass the systemic vascular resistance and the pressure in the aorta or pulmonary artery depending on whether it is the left or right ventricle, respectively. The correct choice highlights that afterload is fundamentally about the load against which the heart works during contraction to pump blood out. It reflects the resistance the heart faces from the blood vessels, which can be affected by vascular tone and blood viscosity among other factors. Understanding afterload is essential for addressing conditions such as hypertension or heart failure, where elevated afterload can lead to increased cardiac workload and may contribute to the decline in heart function over time. The other options describe different aspects of cardiac physiology. The pressure required to fill the heart pertains more to preload, the volume of blood pumped per minute relates to cardiac output, and the rate of heart contraction is a concept associated with heart rate or contractility, none of which encapsulate the definition of afterload.