What do cardiac preload and afterload mean?

Cardiac preload and afterload are two loads that affect the strength and speed of the heart's contractions.

Cardiac preload is the resistance to blood flow from the veins of the body back to the heart, also known as diastolic load. It is the pressure that the heart needs to overcome to push venous blood flow back. Systemic changes in blood volume, such as large amounts of fluid in a short period of time, hyperthyroidism, chronic anemia, etc., can increase preload.

Cardiac afterload is the pressure that the heart needs to drive blood through the systemic circulation and counter arterial rebound, also known as systolic load. When cardiac afterload increases, the heart needs more force to overcome these resistances, resulting in greater systolic pressure.