Which statement best defines preload and afterload?

Which statement best defines preload and afterload?

• A. Preload is ventricular stretch at end-diastole; afterload is the resistance the left ventricle must overcome to eject blood
• B. Preload is the rate of heart contraction; afterload is diastolic blood pressure
• C. Preload is stroke volume; afterload is central venous pressure
• D. Preload is right ventricular pressure; afterload is pulmonary artery pressure

Answer: (D)

Preload is the filling state of the ventricle at end-diastole, reflected by the end-diastolic pressure. In the right ventricle, this filling pressure is best understood as the right ventricular end-diastolic pressure, which parallels venous return. Afterload is the pressure the ventricle must overcome to eject blood; for the right ventricle, that resistance is the pulmonary artery pressure (pulmonary vascular resistance). So, describing preload as right ventricular pressure and afterload as pulmonary artery pressure fits how the right heart fills and then pumps into the pulmonary circulation. The other formulations mix up preload with contractility, rate of contraction, diastolic BP, or stroke volume, which don’t capture the correct relationships.

Preload is the filling state of the ventricle at end-diastole, reflected by the end-diastolic pressure. In the right ventricle, this filling pressure is best understood as the right ventricular end-diastolic pressure, which parallels venous return. Afterload is the pressure the ventricle must overcome to eject blood; for the right ventricle, that resistance is the pulmonary artery pressure (pulmonary vascular resistance). So, describing preload as right ventricular pressure and afterload as pulmonary artery pressure fits how the right heart fills and then pumps into the pulmonary circulation. The other formulations mix up preload with contractility, rate of contraction, diastolic BP, or stroke volume, which don’t capture the correct relationships.