The acute onset of severe aortic regurgitation (AR, also called aortic insufficiency) is usually a medical emergency due to the inability of the left ventricle to quickly adapt to the rapid increase in end-diastolic volume caused by regurgitant blood. If not surgically corrected, acute severe AR commonly results in cardiogenic shock. In contrast, clinical symptoms are a relatively late feature of chronic AR, since the gradually dilating left ventricle and compensatory mechanisms dampen many of the hemodynamic abnormalities resulting from chronically increased diastolic volumes

The causes of acute aortic regurgitation (AR) with a native aortic valve are limited and include:

●Endocarditis – Endocarditis results in valve destruction and leaflet perforation. In addition, aortic perivalvular abscess may rupture into the left ventricle, resulting in AR, or into the left atrium or right ventricular outflow tract, with a clinical presentation that mimics acute aortic regurgitation.
●Aortic dissection – Aortic dissection can result in AR by four mechanisms: dilation of the sinuses with incomplete coaptation of the leaflets at the center of the valve; involvement of a valve commissure resulting in inadequate leaflet support; direct extension of the dissection into the base of a leaflet, resulting in a flail valve leaflet; and prolapse of the dissection flap across the aortic valve into the left ventricular outflow tract in diastole impeding leaflet closure. Patients with a bicuspid aortic valve are at higher risk of aortic dissection