Moderate to severe MR typically results in dilation of which structures?

Moderate to severe MR typically results in dilation of which structures?

• A. Right ventricle
• B. Left atrium only
• C. Left ventricles and left atrium
• D. Right atrium

Answer: (C)

Moderate to severe mitral regurgitation causes volume overload on the left heart. During systole, some blood leaks back into the left atrium, so the left atrium receives more blood than normal and enlarges over time. At the same time, the left ventricle must handle the normal forward flow plus the regurgitated volume, increasing its end-diastolic volume and leading to LV dilation as an adaptive response. This combination—enlargement of both the left atrium and left ventricle—is characteristic of significant MR. Right-sided chambers are not typically dilated from MR alone unless there is later development of pulmonary hypertension or other right-heart disease.

Moderate to severe mitral regurgitation causes volume overload on the left heart. During systole, some blood leaks back into the left atrium, so the left atrium receives more blood than normal and enlarges over time. At the same time, the left ventricle must handle the normal forward flow plus the regurgitated volume, increasing its end-diastolic volume and leading to LV dilation as an adaptive response. This combination—enlargement of both the left atrium and left ventricle—is characteristic of significant MR. Right-sided chambers are not typically dilated from MR alone unless there is later development of pulmonary hypertension or other right-heart disease.