Effect of atropine-dobutamine stress test on left ventricular echocardiographic parameters in untrained warmblood horses.
Authors: Sandersen Charlotte F, Detilleux Johanne, de Moffarts Brieuc, Van Loon Gunther, Amory Hélène
Journal: Journal of veterinary internal medicine
Summary
Pharmacological stress echocardiography using combined atropine and dobutamine offers a non-exercise method for evaluating cardiac contractility in horses, yet its diagnostic utility remains underdeveloped in equine medicine. Researchers administered incremental dobutamine infusions (2–6 µg/kg/min) following atropine (35 µg/kg IV) to seven untrained warmbloods aged 9–22 years, measuring left ventricular dimensions and function via B- and M-mode echocardiography at baseline and during pharmacological challenge. The protocol successfully stressed the heart, achieving a maximum heart rate of 156.6 ± 12.5 bpm, and elicited robust contractile responses: fractional shortening improved significantly from 35% to 50.6%, whilst wall thickness and interventricular septal thickness increased dose-dependently, with left ventricular internal dimensions decreasing as expected during positive inotropic stimulation. For practitioners, these findings establish baseline echocardiographic parameters during controlled pharmacological stress in healthy horses, creating a reference framework for identifying abnormal contractile responses that might indicate underlying cardiac pathology—particularly valuable for pre-purchase assessment or investigating exercise intolerance when traditional resting echocardiography appears unremarkable. Future work must determine whether blunted or exaggerated responses to this stress protocol correlate with clinical cardiac disease, which would substantially improve early detection of conditions affecting performance.
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Practical Takeaways
- •Atropine-dobutamine stress echocardiography produces reliable, measurable changes in left ventricular function in healthy warmblood horses and may be useful as a diagnostic protocol
- •This pharmacological stress test could potentially differentiate horses with cardiac disease from healthy individuals, but further research is needed to establish clinical utility
- •The protocol achieved adequate heart rate elevation (156.6 bpm) comparable to exercise stress, offering a controlled alternative for horses unable to perform exercise testing
Key Findings
- •Heart rate increased significantly to 156.6 ± 12.5 bpm at maximal dobutamine infusion (6 microg/kg/min)
- •Fractional shortening increased significantly from 34.98 ± 3.82% at baseline to 50.56 ± 3.42% at maximal dobutamine infusion
- •Left ventricular wall thickness (interventricular septum and free wall) increased significantly during pharmacological stress testing
- •Left ventricular internal diameter decreased significantly during dobutamine infusion, indicating positive systolic response to stress