A comparison of dobutamine infusion to exercise as a cardiac stress test in healthy horses.
This study was done to determine whether administration of dobutamine would produce echocardiographic and electrocardiographic alterations comparable to those induced by treadmill exercise in healthy horses. Fourteen horses received maximal treadmill exercise and, separately, intravenous dobutamine infusion up to a maximum rate of 50 microg/kg/min. Ten of the 14 horses were euthanized, and the myocardial tissues were examined grossly and histopathologically. No significant differences were found in the chronotropic effects of dobutamine and exercise (P = .905). Dobutamine induced greater interventricular septal thickening during systole (dobutamine = 4.78 cm, exercise = 4.03 cm; P = .004). and greater left ventricular diameters during diastole (dobutamine = 9.73 cm, exercise = 9.26 cm; P = .037), than did exercise treatment. Horses exhibited transient signs of sweating and restlessness during infusion of moderate to maximum doses of dobutamine. Ventricular ectopy seen in 11 of 14 horses was attributed to the arrhythmogenic properties of dobutamine, as well as to increased vagal tone present at low dobutamine doses. Myocardial lesions characteristic of catecholamine myotoxicity were present in 2 of the 10 horses examined. Although dobutamine induces chronotropic and inotropic changes similar to those induced by exercise, the use of high-dose dobutamine as a cardiac stressor in horses cannot be advocated because of potential development of arrhythmias or myotoxicity.
Frye
M A
MA
Department of Clinical Sciences, Colorado State University, Fort Collins, CO, USA. melinda.frye@uchsc.edu
Bright
J M
JM
Dargatz
D A
DA
Fettman
M J
MJ
Frisbie
D D
DD
Baker
D C
DC
Traub-Dargatz
J L
JL
D000318:Adrenergic beta-Agonists / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000139:chemically induced / Q000662:veterinary; D004280:Dobutamine / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography; D005080:Exercise Test; D006262:Health; D006321:Heart / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology; D006331:Heart Diseases / Q000139:chemically induced / Q000662:veterinary; D006339:Heart Rate / Q000187:drug effects; D006734:Horse Diseases / Q000139:chemically induced; D006736:Horses / Q000502:physiology*; D010805:Physical Conditioning, Animal / Q000502:physiology*
D000318:Adrenergic beta-Agonists; D004280:Dobutamine