The so-called cardiac preload refers to the resistance or load encountered by the heart prior to contraction, often also called volume load. And by afterload, I mean the resistance or load encountered by the heart after contraction, usually called pressure load. What are the factors that affect the preload of the heart? The factor that most often affects it is blood volume, which is the effective amount of blood circulating in the body. For example, massive transfusions, hyperthyroidism, and chronic anemia can cause an increase in blood volume, which can increase the preload of the heart. In contrast, massive bleeding, severe diarrhea, vomiting, etc. cause a decrease in blood volume, which will reduce the preload of the heart. The most common cause of increased afterload in the left ventricle is hypertension, while the most common cause of increased afterload in the right ventricle is pulmonary hypertension.