Which parameter is used to define Stage B2 on echocardiography?

• A. LA:Ao ratio
• B. LV wall thickness
• C. Aortic diameter
• D. Right atrial size

Answer: (A)

Stage B2 reflects left-sided remodeling from mitral valve disease in dogs that are asymptomatic. The measurement that defines this stage on echocardiography is the left atrial to aortic root diameter ratio. This ratio directly shows how enlarged the left atrium is relative to a stable reference (the aorta), and when it crosses about 1.6, it indicates significant atrial dilation consistent with remodeling. Other options don’t specifically capture the left atrial enlargement that marks progression to this stage: LV wall thickness can vary by breed and isn’t a direct indicator of this remodeling stage; the aortic diameter alone doesn’t reflect atrial size; right atrial size points to right-sided changes rather than the left-sided remodeling central to this stage.