Effect of atropine-dobutamine stress test on left ventricular echocardiographic parameters in untrained warmblood horses.

The research paper evaluates the impact of a combined atropine low-dose dobutamine stress test on the left ventricular parameters of adult warmblood horses. The test induced significant changes in various cardiac parameters and the paper suggests further studies to analyze its value for horses with cardiac diseases.

Objective of the Research

• The primary objective of this study was to understand the impact of a combined atropine low-dose dobutamine stress test on the left ventricular parameters in adult warmblood horses. This was done with a view to establishing a possible pharmacological stress echocardiography protocol.

Methodology and Subjects

• Seven healthy untrained warmblood horses aged between 9 to 22 years were used in this study.
• The heart rate and left ventricular B- and M-mode dimensions were recorded at baseline and during the stress test which involved 35 microg/kg intravenous atropine followed by an incremental dobutamine infusion of 2 to 6 microg/kg/min.

Results and Findings

• The heart rate significantly increased during the pharmacological challenge, reaching a maximal average rate of 156.6 +/- 12.5 beats per minute at the highest dobutamine infusion rate.
• Both systolic (contracting state of the heart) and diastolic (relaxing state of the heart) measurements of the interventricular septum thickness, left ventricular free wall thickness, along with fractional shortening, also significantly increased peaking at the highest infusion rate.
• In contrast, the left ventricular internal diameter decreased significantly during dobutamine infusion.
• At a dobutamine infusion rate of 2 microg/kg/min, left ventricular external and internal area were significantly lower, but no further decrease was observed during subsequent steps. However, the systolic and diastolic myocardial area was significantly lower post the administration of dobutamine but remained statistically constant during further dobutamine infusion.

Conclusion and Further Research

• The aforementioned pharmacological stress test led to significant changes in the left ventricular echocardiographic parameters in adult warmblood horses.
• However, the study recommends additional research to assess the utility of this stress test in horses suffering from cardiac diseases.