: Left atrial (LA) function plays an important role in diastolic dysfunction in cats with hypertrophic cardiomyopathy (HCM). Two-dimensional speckle tracking echocardiography (2D-STE) is a novel technique for assessing LA function. This study aimedto evaluate changes in the LA function inHCM cats compared to normal cats, using 2D-STE. Results: Seventeen client-owned cats affected with HCM and twenty healthy control cats. Conventional echocardiographic and 2D-STE variables were measured and

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... red between groups (the normal and HCM groups). The difference between two groups was compared by using the independent Student's t-test. A p -value less than 0.05 was considered significant. Variability from the 2D-STE variables tests displayed good reproducibility (coefficient of variation ≤15%). The mean value of peak atrial longitudinal strain (PALS) in the HCM group (13.16 ± 8.64) was lower in the control group (28.54 ±10.31) ( p < 0.001). PALS was lowest at the LA roof region. The atrial longitudinal strain of septal and lateral regions was significantly lower in the HCM group than the normal group. PALS correlated with the percentage of the LA fractional shortening (LA-FS) (r=0.538, p =0.001), the percentage of the LA ejection fraction (LA-EF) (r =0.797, p <0.001), and the LA fractional area change (FAC) (r =0.746, p <0.001). Conclusions: PALS can be used to evaluate changes in theLA function in HCM cats. It is a reproducible method for assessing the LA function in cats affected with HCM. Keywords cats; heart; left atrium; strain Background Hypertrophic cardiomyopathy (HCM) is one of the most common myocardial diseases. The prevalence of HCM in cats was approximately 10-15% in cats and increased with age [1,