What is afterload?

• A. The pressure the ventricle must overcome to eject blood (arterial pressure/impedance)
• B. The volume of blood ejected per beat
• C. The time between two heartbeats
• D. The heart rate

Answer: (A)

Afterload is the pressure the ventricle must overcome to eject blood into the arterial system during systole. It reflects the arterial pressure and the resistance (impedance) the heart faces as it pumps, so higher arterial pressure, stiffer arteries, or increased vascular resistance raise afterload. This is why conditions like hypertension or aortic stenosis make the heart work harder to push blood out. It’s not about how much blood is ejected per beat (that’s stroke volume), nor about the time between beats or the heart rate. When afterload goes up and the ventricle can’t increase its force enough, stroke volume tends to decrease because ejection becomes harder. Conversely, lower afterload makes ejection easier.