Effect of physiological and pharmacological stress on heart rate, blood pressure, and echocardiographic measurements in healthy Warmblood horses.
Authors: Dufourni Alexander, Buschmann Eva, Vernemmen Ingrid, Van Steenkiste Glenn, van Loon Gunther, Decloedt Annelies
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Stress-induced changes in equine cardiac measurements Echocardiography provides valuable prognostic information in horses, yet the influence of heart rate and blood pressure on these measurements remains incompletely understood—a concern when tracking serial changes over time. Researchers examined 20 healthy Warmbloods across three conditions (rest, physiological stress, and pharmacological challenge using butylscopolammonium bromide and metamizol sodium) whilst recording comprehensive echocardiographic data, blood pressure and ECG simultaneously. Physiological stress (heart rate rising to 46 bpm) modestly enhanced left atrial function and late diastolic wall motion velocity but left most measurements unchanged, whereas pharmacological challenge (reaching 62 bpm) produced more pronounced alterations including reduced left atrial and ventricular diastolic dimensions, increased aortic and pulmonary diameters, and thickened ventricular walls. These findings underscore that even moderate elevations in heart rate substantially alter measurable cardiac dimensions and function, emphasising the importance of standardised resting conditions during echocardiographic examination and caution when comparing studies conducted at different heart rates—a particular consideration for practitioners monitoring chronic conditions or screening performance horses before and after exertion.
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Practical Takeaways
- •Echocardiographic measurements must account for heart rate and blood pressure at time of examination; comparisons between repeated exams are only valid when cardiovascular parameters are similar
- •Mild physiological stress (such as that occurring during routine handling) minimally affects most cardiac dimensions, but pharmacological agents used clinically can substantially alter measurements and should be avoided before cardiac ultrasound when serial comparison is planned
- •When evaluating horses with suspected cardiac disease or monitoring cardiac function over time, standardize examination conditions by obtaining measurements at similar resting heart rates and blood pressures to ensure reliable trend analysis
Key Findings
- •Heart rate increased from 34 bpm at rest to 46 bpm with physiological stress and 62 bpm with pharmacological challenge; systolic blood pressure increased from 86 to 93 and 107 mm Hg respectively
- •Physiological stress significantly increased left atrial fractional area change (34.3% vs 27.3%) and left ventricular late diastolic radial wall motion velocity (13 vs 10 cm/s)
- •Pharmacological challenge resulted in significantly decreased left ventricular internal diameter (10.3 vs 10.7 cm), increased aortic and pulmonary diameters, and increased ventricular wall thickness compared to rest
- •Most echocardiographic variables remained unchanged during physiological stress at mild heart rate elevation, but pharmacological challenge altered cardiac dimensions substantially