1. Definition
Afterload is defined as the pressure that the heart must overcome in order to eject blood during systole.
2. Physiology of Afterload
The afterload exerts a direct influence on cardiac performance, as it determines the force that the ventricles must generate during contraction to overcome end-diastolic aortic and pulmonary pressure. The primary determinants of afterload are systemic vascular resistance (SVR), arterial pressure and arterial compliance. An elevated afterload necessitates a greater cardiac output to maintain effective blood pumping.
3. Pathophysiology
An increased afterload can contribute to the development of various cardiac conditions, such as left ventricular hypertrophy, due to the increased workload imposed on the heart over time. Hypertension and aortic stenosis are two common causes of increased afterload, which in turn leads to structural and functional changes in the heart.
4. Factors Influencing Afterload
- Systemic Blood Pressure
- Arterial Stiffness and Vascular Resistance
- Heart Valve Condition
- Blood volume and viscosity
5. Increase in Afterload
An increase in afterload may occur in response to various factors, including hypertension and aortic valve stenosis. These conditions elevate the resistance encountered by the heart during ejection, contributing to an overall rise in afterload. This can result in a reduction in cardiac output and an increased demand for oxygen by the myocardium, which may ultimately lead to heart failure if left unmanaged.
6. Decrease in Afterload
A reduction in afterload may be achieved through vasodilation, decreased systemic vascular resistance, or the use of certain medications. A reduction in afterload allows for the easier ejection of blood from the heart, thereby improving cardiac output and reducing the heart’s workload.