American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the main indicator for determining the severity of aortic regurgitation?

1. Vmax measurement

2. Left ventricular dimensions

3. Mean gradient

4. Regurgitant fraction

The correct answer is: Regurgitant fraction

The severity of aortic regurgitation is primarily determined by the regurgitant fraction, which quantifies the volume of blood that leaks back into the left ventricle during diastole relative to the total stroke volume. A higher regurgitant fraction indicates a greater amount of backflow, which is directly related to the severity of the condition. This measurement reflects both the volume of regurgitated flow as well as the hemodynamic impact on the left ventricle, making it a crucial factor in assessing the progression and potential consequences of aortic regurgitation. While the left ventricular dimensions are important in the overall assessment of the heart's response to aortic regurgitation, they serve more as a consequence of the regurgitation rather than a direct measure of severity. Similarly, the mean gradient across the valve can provide some information about the pressure differences but does not directly reflect the volume of regurgitation like the regurgitant fraction does. The measurement of Vmax (peak velocity) is more commonly associated with stenotic lesions rather than regurgitation severity. In summary, the regurgitant fraction is the key indicator used to evaluate the severity of aortic regurgitation, as it illustrates the extent of the backflow and