# Monoplane Simpson’s Method Is Reliable for Left Atrial Volume Assessment in Small Dogs with Myxomatous Mitral Valve Disease

## TL;DR

This study finds that the monoplane Simpson’s method is a reliable and practical way to measure left atrial volume in small dogs with heart disease.

## Contribution

The study demonstrates the clinical utility and practicality of the monoplane Simpson’s method for left atrial volume assessment in small dogs.

## Key findings

- Both monoplane Simpson’s and biplane area–length methods effectively distinguish dogs with cardiac remodeling.
- The two methods are not interchangeable, with differing cutoff values for left atrial volume assessment.
- The monoplane Simpson’s method is recommended for routine clinical use due to its simplicity and practicality.

## Abstract

Left atrial enlargement is a key sign of heart disease progression in dogs with myxomatous mitral valve disease. This study compared two echocardiographic techniques—the monoplane Simpson’s method, which uses a single image view, and the biplane area–length method—to measure left atrial volume in small-breed dogs. Both methods effectively distinguished dogs with cardiac remodeling, but the results were not interchangeable, and their cutoff values differed. The monoplane Simpson’s method is straightforward and practical for routine veterinary use. Consistently applying one method and using the given cutoff values can help veterinarians monitor disease and support treatment decisions in daily practice.

Left atrial enlargement is a key marker of disease progression and prognosis in dogs with myxomatous mitral valve disease. Echocardiographic assessment of left atrial volume provides a more comprehensive measure than linear dimensions, yet different two-dimensional methods may yield variable results. This study aimed to compare the monoplane Simpson’s method of discs and the biplane area–length method for estimating left atrial volume indexed to body weight in dogs across different stages of disease. Dogs were prospectively evaluated with transthoracic echocardiography, and left atrial volumes were calculated using both techniques. Both indices clearly distinguished dogs with enlarged atria from controls and stage B1 patients. However, the two methods were not interchangeable, regardless of atrial size, as demonstrated by the Bland–Altman analysis. In conclusion, both techniques are clinically useful for assessing left atrial remodeling, but because they are not interchangeable, clinicians should consistently use one method. The monoplane Simpson’s method may be particularly practical for routine clinical application due to its convenience.