Age is a major risk factor for cardiovascular disease, yet quantitative data on age-related myocardial changes in dogs using two-dimensional speckle tracking echocardiography (2D-STE) remain limited. This study aimed to establish preliminary reference data for myocardial strain (St) and strain rate (SR) using 2D-STE in healthy dogs and to compare these parameters between young adult and old dogs. Ten young adult and ten old clinically healthy dogs underwent conventional echocardiography and 2D-STE. Peak systolic St, peak systolic SR, early diastolic SR, and late diastolic SR were measured in radial, circumferential, and global longitudinal directions. Standard echocardiographic parameters, including left ventricular dimensions, fractional shortening, and tissue Doppler-derived early diastolic velocity, did not differ significantly between groups. However, the E/A ratio and late diastolic tissue velocity (Am) were significantly lower in old dogs. In 2D-STE analysis, systolic St and SR across all directions did not differ between groups. In contrast, early diastolic radial, circumferential, and global longitudinal SR were significantly reduced in old dogs, while late diastolic radial SR was higher in selected segments. These findings indicate that while systolic myocardial deformation remains preserved with age, diastolic deformation parameters exhibit significant age-related alterations. This study provides age-specific preliminary reference data for left ventricular myocardial deformation using 2D-STE in healthy dogs.

Abstract
INTRODUCTION
MATERIALS AND METHODS
    Animals
    Conventional echocardiography
    Speckle tracking echocardiography
    Statistical analysis
RESULTS
    Conventional echocardiography
    Segmental radial and circumferential deformationwithin groups
    Comparison between young and elderly dogs
DISCUSSION
REFERENCES

• Chang-Ho Shin(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, South Korea)
• Tae Sung Hwang(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, South Korea)
• Hee Chun Lee(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, South Korea) Corresponding author