Right ventricular function during pharmacological and exercise stress testing in horses.
Authors: Decloedt A, De Clercq D, Ven S, Vera L, van Loon G
Journal: Veterinary journal (London, England : 1997)
Summary
During intense exercise, horses experience a threefold increase in pulmonary artery pressure, which can trigger right ventricular remodelling and potentially compromise cardiac function—a concern shared with human endurance athletes. Decloedt and colleagues compared right ventricular responses in ten healthy horses using two stress protocols: treadmill exercise and pharmacological stress via atropine-dobutamine infusion, measured by echocardiography at peak effort and immediately post-exercise. Although systemic haemodynamics (heart rate, blood pressure, cardiac output) were comparable between the two protocols, pulmonary artery pressures diverged markedly: exercise induced systolic pressures of 121 mmHg compared to only 69 mmHg during pharmacological stress, with post-exercise values remaining elevated at 93 mmHg. Right ventricular function also differed substantially—fractional area change (a key measure of contractility) decreased to 40.5% post-exercise but paradoxically increased to 72.6% during pharmacological stress—indicating that the right ventricle was actually working harder and less efficiently under exercise conditions. For equine professionals involved in conditioning athletic horses or assessing cardiac health, this research underscores that pharmacological stress testing cannot replicate the pulmonary haemodynamic demands of actual exercise; treadmill testing or on-track assessment remains essential for accurately evaluating right ventricular function and identifying horses at risk of exercise-induced pulmonary hypertension and subsequent cardiac compromise.
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Practical Takeaways
- •Exercise-induced pulmonary hypertension in horses causes acute right ventricular changes that pharmacological stress cannot replicate; clinicians should use actual exercise testing when assessing athletic cardiac function
- •Endurance horses show significant transient right ventricular strain post-exercise with reduced contractility; recovery and monitoring protocols should account for this acute stress period
- •Cardiac troponin elevation post-pharmacological stress may indicate myocardial microtrauma; use caution interpreting troponin as a biomarker of exercise-induced cardiac damage without concurrent functional imaging
Key Findings
- •Systolic pulmonary artery pressure was significantly higher during exercise (121±15 mmHg) and post-exercise (93±10 mmHg) compared to pharmacological stress (69±12 mmHg)
- •Right ventricular fractional area change decreased post-exercise (40.5±6.2%) versus increased during pharmacological stress (72.6±7.3%)
- •Right ventricular diameters and systolic right to left ventricular area ratios were higher post-exercise than during pharmacological stress
- •Pharmacological stress testing does not adequately reproduce the cardiovascular effects of exercise in horses and is not suitable for studying right ventricular athletic adaptations