What it means
The heart must create more pressure than the blood vessels hold in order to open the valves and eject blood. Tight, narrow arteries and high blood pressure raise afterload, as does a narrowed aortic valve. A high afterload makes the heart work harder and, over time, can thicken and weaken it. Drugs that widen arteries, such as ACE inhibitors, lower it.
Remember it
Afterload is what the heart pushes against after it starts to squeeze.
Related terms
hypertension
Blood pressure that stays higher than normal, at or above 130/80 mm Hg by current US guidelines.
cardiac output
The amount of blood the heart pumps out in one minute.
preload
How much the heart's ventricles are stretched by the blood filling them just before they squeeze.
mean arterial pressure
The average pressure in the arteries over one heartbeat, used as a measure of how well blood reaches the organs.