The mechanism of aortic insufficiency (AI), comprises the pressure in the left ventricle falling below the pressure in the aorta, the aortic valve is not able to completely close. This causes a leaking of blood from the aorta into the left ventricle. This means that some of the blood that was already ejected from the heart is "regurgitating" back into the heart. The percentage of blood that regurgitates back through the aortic valve due to AI is known as the regurgitant fraction. This regurgitant flow causes a decrease in the diastolic blood pressure in the aorta, and therefore an increase in the pulse pressure. Since some of the blood that is ejected during systole regurgitates back into the left ventricle during diastole, "there is decreased effective forward flow in AI".