Atropine reduces dobutamine-induced side effects in ponies undergoing a pharmacological stress protocol.
Authors: Sandersen C F, Detilleux J, Delguste C, Pierard L, van Loon G, Amory H
Journal: Equine veterinary journal
Summary
# Pharmacological Stress Testing in Equines: Atropine-Modified Dobutamine Protocol Shows Promise Dobutamine stress echocardiography offers a valuable alternative to treadmill exercise testing for evaluating cardiac function under load, yet high-dose protocols carry significant risks of arrhythmias and cardiotoxicity in horses. Researchers investigated whether atropine pretreatment could mitigate these adverse effects whilst maintaining diagnostic utility, testing two dobutamine infusion protocols in 13 Shetland ponies using pulsed-wave Doppler ultrasound to measure heart rate, stroke index and cardiac index at baseline and during incremental drug dosing. Ponies pretreated with atropine (two 25 µg/kg injections) receiving low-dose dobutamine achieved a 2.5-fold increase in cardiac index compared to their resting values, with this improvement driven entirely by increased heart rate whilst stroke index remained stable; notably, this group showed no arrhythmias or excessive restlessness, unlike the untreated group that exhibited marked side effects and variable cardiac responses. The atropine-modified protocol appears to deliver the haemodynamic stress stimulus necessary for cardiac assessment without triggering the autonomic-mediated dysrhythmias and behavioural disturbances that complicate conventional high-dose approaches. For practitioners, this work suggests a safer pathway to pharmacological stress testing in equids, though further investigation of left ventricular wall motion changes and validation in horses (rather than ponies alone) will be essential before widespread clinical adoption.
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Practical Takeaways
- •Low-dose dobutamine stress echocardiography with atropine premedication offers a safer alternative to high-dose protocols for cardiac evaluation in equines without requiring treadmill exercise
- •Atropine pretreatment reduces adverse effects (arrhythmias and behavioral distress) while maintaining diagnostic cardiac response, improving both safety and animal welfare during the procedure
- •This protocol could enable more consistent and reliable cardiac assessment in clinical practice, though further validation in horses is needed before widespread adoption
Key Findings
- •Low-dose dobutamine (2-5 microg/kg bwt/min) with atropine premedication produced 2.5× increase in cardiac index compared to higher-dose dobutamine alone
- •Atropine pretreatment prevented excessive restlessness and cardiac arrhythmias that occurred in the non-pretreated group
- •Cardiac index increase was mediated by heart rate elevation in both groups, but stroke index only decreased significantly without atropine pretreatment
- •Atropine-pretreated ponies showed lower intragroup variability in cardiac response to pharmacological challenge