American Board of Internal Medicine (ABIM) Certification Practice Exam

What regurgitant fraction (RF) indicates severe mitral regurgitation?

1. Less than 30%

2. 30%-49%

3. 50% or greater

4. Exactly 40%

The correct answer is: 50% or greater

The regurgitant fraction (RF) is a critical measurement used to assess the severity of mitral regurgitation. It quantifies the proportion of the total stroke volume that is regurgitant flow back through the valve instead of being propelled forward into the systemic circulation. In cases of mitral regurgitation, a regurgitant fraction of 50% or greater indicates severe disease. This threshold is significant because at this level, there is substantial volume overload in the left atrium and left ventricle, leading to noticeable symptoms and requiring close clinical management. Patients with an RF in this range often present with signs of heart failure or have an increased risk of developing complications such as atrial fibrillation or pulmonary hypertension due to the chronic volume overload. Therefore, detecting an RF of 50% or greater is essential for proper diagnosis and therapeutic decisions regarding interventions like surgical repair or valve replacement. Lower regurgitant fractions (like those below 50%) suggest milder forms of mitral regurgitation, which may be managed differently and are less likely to result in immediate or aggressive treatment. This distinction is fundamental when evaluating patients with mitral valve pathology.