Due to incapacity to close the aortic valve well enough to resist the aortic pressure, blood will leak back into the left ventricle during diastole, imposing increased ventricular volume load. This is the essential problem with AR; the left ventricle must work harder to provide sufficient cardiac output over a prolonged period and is chronically overtaxed. The result of volume overload is that the ventricle becomes dilated. A dilated ventricle will demand more oxygen to perform its task, and the patient will consequently be at higher risk for left ventricular ischemia and angina pectoris.

The volume overload of the ventricle is compensated by dilatation of the heart. With dilatation, mean diastolic pressure remains normal and the state of ventricular growth can easily be ignored in physical exams. It is therefore always important to be suspicious of any diastolic murmurs that is often the only early clue to ventricular overload. 

• In calcific disease AR is often present but usually at a trivial level.
• With bicuspid aortic valve and in rheumatic disease it may the dominant lesion.
• Aortic root diseases can cause chronic AR by dilatation of the valve annulus. (Marfan’s Syndrome, Hypertension and more)
• Acute AR can be caused valvular ruptures or damages secondary to infective endocarditis or aortic dissection.