Afterload is the hemodynamic parameter that reflects the force that the left ventricle has to overcome to eject blood through the aortic valve.
The most common pathologic process that increases afterload is systemic hypertension. Other situations that increase afterload include aortic stenosis (including subvalvular and supravalvular), aortic regurgitation and coarctation of the aorta.
The afterload can be decreased by any process that lowers blood pressure. Mitral regurgitation also decreases afterload since blood has two directions to leave the left ventricle.
Chronic elevation of the afterload leads to pathologic cardiac structural changes including left ventricular hypertrophy. Eventually this results in diastolic dysfunction and symptoms of diastolic congestive heart failure.