Exercise-induced cardiac remodeling in farm dogs: A comparative echocardiographic and electrocardiographic study.

Objectives: To compare cardiac structure and function of healthy indoor dogs, healthy active farm dogs, and indoor dogs with structural heart disease, and to investigate whether cardiovascular differences are lifestyle-related. Materials and Methods: Thirty-nine client-owned dogs (1-15 years old) were enrolled between January and March 2026. Dogs were grouped into healthy indoor dogs (n = 10), active farm dogs (n = 14), and indoor dogs with structural heart disease (n = 15). Physical exam, electrocardiography, and transthoracic echocardiography were performed in all dogs. Continuous variables were tested for statistical significance, with p < 0.05 indicating significance. Results: Active farm dogs had significantly reduced resting heart rates in comparison to healthy indoor and diseased indoor dogs (p < 0.05). Echocardiography showed that farm dogs had larger normalized left ventricular inner measurements and smaller relative wall thickness than that in healthy indoor dogs (p < 0.05), indicating eccentric remodeling. However, the farm dogs were also significantly younger and heavier (p < 0.05). Dogs with heart disease had significantly greater left atrial size and differed in functional indices from those in the healthy group (p < 0.05). Cardiac murmurs occurred in all groups. Conclusions: Cardiac morphology and functional features differed among dogs with different lifestyles and disease severity. Active farm dogs showed signs of physiological eccentric remodeling, although this might have been moderated by age, body size, and breed. Echocardiography remains essential for differentiating structural heart disease from physiological variation. Further study is required on the different effects of exercise on cardiac remodeling in dogs.