Global longitudinal strain is not only prognostically useful, but can also detect subtle changes in left ventricular systolic function, earlier than traditional measures like ejection fraction (and certainly earlier than fractional shortening!). In cats with hypertrophic cardiomyopathy in particular, blind reliance on ejection fraction can give us a false impression of LV systolic function; assessing longitudinal function is far more revealing.

In our lab, we assess global longitudinal strain (GLS) by calculating the change in length of the endocardial curve, which tracks around the endocardium from the septal mitral annular hinge point, through the apex, and down to the lateral mitral annular hinge point, in a horseshoe shape. With the apex as a fixed point, you can imagine how the overall shortening of the length of the curve during systole is so heavily influenced by the ventricle's longitudinal function.

This method has been validated in humans (Stowell et al., 2024), and is particularly suited to small animals since it eradicates the main barriers to using strain in small animal echocardiography. Traditional ways of calculating GLS by speckle tracking require good image quality, and high frame rates. This can often mean that obese patients are excluded due to suboptimal image quality, and many feline patients or nervous dogs are excluded due to very fast heart rates. Our technique is also vendor-neutral, meaning we can analyse echocardiograms performed on other machines using our software, to track change over time.

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