Left atrial strain response to acute preload reduction in healthy dogs using a translational blood donation model

Left atrial function (LAF) is crucial to hemodynamics, but the effects of preload variation on its echocardiographic indices remain unclear. This study aimed to identify preload-independent phasic LA echocardiographic variables and to assess blood donor dogs as a hypovolemia model. Twenty-six healthy, client-owned dogs underwent transthoracic echocardiography before and after standardized blood donation. Phasic LA volumes and strain parameters were assessed, and a subgroup of dogs donating ≥ 10 mL/kg was also analyzed. After blood withdrawal, significant reductions were observed in maximum LA volume (p = 0.0350), LA ejection volume and LA ejection fraction (p = 0.0204), reservoir strain (p = 0.0149), and contractile strain (p = 0.0149), confirming their preload dependency. Conversely, minimum volume (p = 1.0000), pre-atrial contraction volume (p = 0.4373), and conduit strain (p = 0.2156) did not change significantly in the subgroup, indicating lower sensitivity to acute volume variation. These results demonstrate that different LA functional phases respond differently to preload changes and suggest that some parameters may be more stable for clinical interpretation under variable hemodynamic conditions. The blood donation model proved to be a practical and ethically acceptable method for assessing preload-dependent variables in conscious dogs.