Exercise and pharmacological stress echocardiography in healthy horses.

The research article focuses on the use of stress echocardiography in horses, comparing the effects of exercise and pharmacological stress tests on the left ventricular parameters of the heart. It suggests that the pharmacological stress test may be a more useful diagnostic tool for identifying exercise-induced myocardial dysfunction.

Objective and Methods of the Study

• The goal of the study was to evaluate how treadmill exercise and pharmacological stress tests influenced the echocardiographic parameters of the left ventricle in horses.
• The researchers performed echocardiography on two groups of five healthy horses. One group was assessed immediately after intense treadmill exercise (Group EXE). The other group underwent a pharmacological stress test (Group DOB) consisting of a 35 microg/kg atropine dose, followed by increasing dobutamine infusion rates for a 5 minute duration each, cumulating to a total dobutamine dose of 100 microg/kg.
• The left ventricular M-mode echocardiographic parameters were compared before and after the stimulus in both groups. The heart rates considered for comparison were 80, 100, 110, 120 130, and 140 beats per minute.

Findings from the Study

• Echocardiographic measurements couldn’t be made at heart rates of 140 and 130 beats/minute in two horses from the Exercise group, as their heart rates fell too rapidly post-exercise. In the remaining horses of the same group, some had issues with image quality at these high heart rates.
• Values for systolic left ventricular parameters and fractional shortening measured at heart rates of 130 and 140 beats/minute in the Exercise group differed significantly from measurements taken at lower heart rates.
• Horses in the Dobutamine group reached target heart rates of 80 and 100 beats/minute after atropine administration, and during a dobutamine infusion rate of 2 microg/kg body weight per minute. Target heart rates of 110, 120, 130, and 140 beats/minute were achieved at mean dobutamine infusion rates of 2.8 +/- 0.4, 3.2 +/- 0.4, 4.0 +/- 0.7, 5 +/- 0.7 microg/kg body weight per minute, respectively.
• The left ventricular parameters and fractional shortening values at higher heart rates in the Dobutamine group were also significantly different from those at lower heart rates.

Conclusions of the Study

• The study concluded that the pharmacological stress test led to changes in ventricular dimensions with increasing heart rates. This test made obtaining good quality images easier at higher heart rates, as compared to the post-exercise echocardiography where image quality posed considerable difficulty.
• This suggests that pharmacological stress echocardiography might be more viable for consistent use in routine clinical settings.
• Furthermore, more studies are needed to confirm the viability of the pharmacological stress test as an effective diagnostic in identifying horses with exercise-induced myocardial dysfunction.