Cardiovascular effects of pimobendan in healthy mature horses.

The research explores the effects of a heart failure drug, pimobendan, usually used in dogs, on the cardiovascular system of healthy mature horses. It was found that intravenous pimobendan induced positive changes in heart rate and heart muscle function, suggesting potential benefits for the treatment of heart failure in horses.

Objective and Methodology

• This research was aimed at studying the cardiovascular effects of pimobendan, an inodilator used in dogs, in horses to facilitate the rational usage of this drug.
• The methodology involved a randomized experiment on five mature horses. Each horse was fasted overnight and then administered with intravenous (i.v.) pimobendan, intragastric (i.g.) pimobendan, or an intragastric placebo, with one week of washout period between each administration.
• To measure the effects of drug administration, horses’ right ventricular (RV) pressure, arterial blood pressure, central venous pressure, cardiac output, and heart rate were monitored before and over an 8-hour period after pimobendan administration.

Results

• The study did not observe any adverse effects related to the pimobendan administration.
• The increase in heart rate was significantly greater in horses given pimobendan both i.v. (36 ± 14%) and i.g. (33 ± 4%) compared to those given a placebo (-2 ± 7%).
• Related to RV pressure, there were significant changes observed with i.v. administration of pimobendan as compared to placebo: the maximum rate of increase in RV pressure (35 ± 36%) and the percentage decrease in minimum pressure (47 ± 24%) and end diastolic pressure (34 ± 13%) were significantly greater.
• However, there were no significant differences in other variables measured between the treatment groups.

Conclusion

• The findings demonstrate that iv pimobendan acted as a chronotropics (increasing heart rate) and an inotropic (altering the strength of muscle contraction) positively in healthy mature horses.
• This suggests that pimobendan could be useful in treating heart failure in horses, although further investigations are needed to support this hypothesis.