Which echocardiographic ratio is used as a criterion for Stage B2 MMVR?

• A. LA:Ao ≤ 1.0
• B. LV:Ao ≥ 1.6
• C. RA:Ao ≥ 1.6
• D. LA:Ao ≥ 1.6

Answer: (D)

In myxomatous mitral valve disease, progression to Stage B2 is defined by evidence of left atrial enlargement due to chronic mitral regurgitation. The left atrial size is most usefully tracked as a ratio to the aorta (LA:Ao) because this normalizes for body size and provides a stable internal reference. A LA:Ao ratio of 1.6 or greater indicates significant atrial remodeling consistent with Stage B2, guiding decisions such as initiating pimobendan therapy to slow progression. The other measurements don’t serve as the standard criterion for Stage B2: LV:Ao, RA:Ao, or a normal LA:Ao below 1.0 do not reflect the threshold used to define this stage.