Stress echocardiography in warmblood horses: comparison of dobutamine/atropine with treadmill exercise as cardiac stressors.
Authors: Gehlen Heidrun, Marnette Silke, Rohn Karl, Stadler Peter
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Stress Echocardiography in Warmblood Horses Evaluating cardiac function during exercise is challenging in equine practice because horses' heart rates drop rapidly after work ceases, leaving only a narrow window for detailed ultrasound assessment. Gehlen and colleagues compared two methods of inducing cardiac stress in ten warmblood horses: treadmill exercise versus pharmacological stress using dobutamine (7.5 µg/kg/min) and atropine (5 µg/kg), measuring electrocardiographic and echocardiographic variables before, during and after each protocol. Treadmill exercise achieved higher peak heart rates (175 ± 10 bpm) but the rapid post-exercise deceleration allowed just one minute for imaging at a mean of 136 ± 8 bpm; by contrast, the drug combination sustained elevated heart rates (141 ± 20 bpm peak, averaging 123 ± 8 bpm) for approximately 7.9 minutes, providing substantially more time for comprehensive measurement. Both stressors produced similar echocardiographic changes—reduced left ventricular dimensions, increased wall thickness and decreased stroke volume—though changes were more pronounced during pharmacological stress. For practitioners performing stress echocardiography, dobutamine and atropine administration offers a practical advantage over exercise by maintaining stable elevated heart rates long enough to obtain detailed cardiac measurements, making it a viable diagnostic tool when assessing suspected cardiac pathology in performance horses.
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Practical Takeaways
- •Pharmacologic stress testing with dobutamine/atropine offers a practical alternative to treadmill exercise for equine cardiac evaluation, particularly when time is limited or exercise conditions are unavailable
- •The prolonged elevated heart rate with drug administration allows veterinarians adequate time to perform detailed ultrasound measurements, unlike the rapid post-exercise heart rate decline
- •Both stress methods identify similar cardiac responses, but dobutamine/atropine may reveal more pronounced abnormalities, potentially improving diagnostic sensitivity for subtle cardiac dysfunction
Key Findings
- •Treadmill exercise achieved higher maximal heart rates (175±10 bpm) compared to dobutamine/atropine (141±20 bpm), but heart rate declined rapidly after exercise
- •Dobutamine/atropine maintained elevated heart rate (123±8 bpm mean) over 7.9 minutes, allowing adequate time for detailed echocardiographic examination
- •Both stressors produced similar echocardiographic changes: decreased LV dimensions, increased LV wall thickness, and reduced stroke volume compared to baseline
- •Dobutamine/atropine combination produced more pronounced echocardiographic changes than treadmill exercise, making it a viable alternative for stress testing in horses