Atropine reduces dobutamine-induced side effects in ponies undergoing a pharmacological stress protocol.
BACKGROUND
High-dose dobutamine stress echocardiography has been shown to be cardiotoxic and arrhythmogenic in horses. However, the test may have benefit in practice as a pharmacological challenge of exercise without the treadmill being required.


OBJECTIVE
To investigate the effect of low-dose dobutamine on cardiac performance in ponies previously treated with atropine, in order to develop a pharmacological protocol that allows examination of the equine heart under stimulation.


METHODS
In 13 healthy Shetland ponies, heart rate (HR), stroke index (SI) and cardiac index (CI) were calculated from pulsed-wave Doppler ultrasound measurements performed at rest and during incremental steps of dobutamine infusion. Group 1 (n = 7) received dobutamine infusion at 2 microg/kg bwt/min for 5 mins followed by incremental rates of 5 microg/kg bwt/min every 5 mins, from 5 to 40 microg/kg bwt/min. Group 2 (n = 6) received dobutamine infusion in incremental rates of 1 microg/kg bwt/min, every 5 mins, from 2 microg/kg bwt/min to 5 microg/kg bwt/min, after premedication with 2 injections of 25 microg/kg bwt of atropine 5 mins apart.


RESULTS
The increase in CI during the pharmacological challenge was higher in Group 2 and reached about 2.5 times the resting value. This increase in CI was mediated by a significant increase in HR in both groups, while SI significantly decreased in Group 1 and did not change significantly in Group 2. Ponies of Group 1, but not those of Group 2, showed excessive restlessness and cardiac arrhythmias during the pharmacological challenge and a high intragroup variability in cardiac response.


CONCLUSIONS
The results of this study suggest that a low dose of dobutamine in ponies previously given atropine could be a helpful pharmacological protocol to perform stress echocardiography in equids.


CONCLUSIONS
Further studies should evaluate left ventricular wall motion in horses undergoing low-dose dobutamine protocol after pretreatment with atropine.
Sandersen
C F
CF
Departments of Clinical Sciences, Large Animal Internal Medicine, University Hospital Liège, University of Liège, Liège, Belgium.
Detilleux
J
J
Delguste
C
C
Pierard
L
L
van Loon
G
G
Amory
H
H
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D001285:Atropine / Q000494:pharmacology*; D002316:Cardiotonic Agents / Q000009:adverse effects*; D003327:Coronary Disease / Q000175:diagnosis / Q000662:veterinary*; D003937:Diagnosis, Differential; D004280:Dobutamine / Q000009:adverse effects*; D004305:Dose-Response Relationship, Drug; D004452:Echocardiography / Q000379:methods / Q000662:veterinary; D005080:Exercise Test / Q000379:methods / Q000662:veterinary; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006734:Horse Diseases / Q000175:diagnosis*; D006736:Horses; D008297:Male; D011897:Random Allocation; D013318:Stroke Volume / Q000187:drug effects / Q000502:physiology
D000889:Anti-Arrhythmia Agents; D002316:Cardiotonic Agents; D004280:Dobutamine; D001285:Atropine