Effect of Atropine-dobutamine Stress Test on Left Ventricular Echocardiographic Parameters in Untrained Warmblood Horses

Abstract

The aim of this study was to investigate the effect of combined atropine low-dose dobutamine stress test on left ventricular parameters in adult warmblood horses, to establish a potential protocol for pharmacological stress echocardiography. Seven healthy untrained warmblood horses aged 9 to 22 years were used. Heart rate (HR) and left ventricular B- and M-mode dimensions were recorded at baseline and during stress testing with 35 microg/kg atropine IV followed by incremental dobutamine infusion of 2 to 6 microg/kg/min. HR increased significantly (P < .05) during the pharmacological challenge, and a maximal HR of 156.6 +/- 12.5 bpm was reached at maximal dobutamine infusion rate. Systolic and diastolic interventricular septum thickness, systolic and diastolic left ventricular free wall thickness, and fractional shortening increased significantly and reached a maximum at the highest infusion rate (mean +/- SD: 4.51 +/- 0.27 versus 5.65 +/- 0.31 cm, 2.89 +/- 0.19 versus 3.78 +/- 0.10 cm, 3.72 +/- 0.34 versus 4.77 +/- 0.18 cm, 2.44 +/- 0.28 versus 3.11 +/- 0.34 cm, 34.98 +/- 3.82 versus 50.56 +/- 3.42%, respectively). Systolic and diastolic left ventricular internal diameter decreased significantly during dobutamine infusion. Left ventricular external and internal area were significantly lower at a dobutamine infusion rate of 2 microg/kg/min but no further decrease was observed during the subsequent steps. Systolic and diastolic myocardial area was significantly lower after the administration of dobutamine but not significantly different during dobutamine infusion, when compared to baseline values. This pharmacological stress test induced significant changes in left ventricular echocardiographic parameters in adult warmblood horses. Additional research should evaluate the value of this stress test in horses suffering from cardiac disease.

Effect of physiological and pharmacological stress on heart rate, blood pressure, and echocardiographic measurements in healthy Warmblood horses

“…Pharmacological challenge with NBBM, a parasympatholytic agent with anticholinergic and antimuscarinic properties, caused similar echocardiographic effects as classical pharmacological stress testing, with decreased left ventricular dimensions and stroke volume and increased relative ventricular wall and interventricular septum thicknesses. 18 , 20 , 23 , 27 Cardiovascular effects of NBBM on HR and BP were visible within 2 minutes after IV administration of NBBM with a gradual reduction to baseline which occurred beyond image acquisition, similar to the findings of Morton et al, 28 who showed significant peak effects on HR and BP within 2 minutes after IV administration of NBB. Peak HR elevation occurred in the study of Morton et al 5 minutes post administration of NBB and persisted 25 minutes for DAP, MAP, and SAP and 50 minutes for HR with a gradual return to baseline.…”

“… 11 , 12 , 13 , 14 , 15 Cardiac dimensions and function were also altered during physiological (treadmill exercise, lunging exercise) or pharmacological stress testing with atropine (parasympatholytic drug), or dobutamine (sympathomimetic drug), with high HR above 80 bpm and important increases in BP. 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 Postexercise evaluation of cardiac variables and pharmacological stress testing demonstrated decreases in left ventricular dimensions with increases in interventricular septum and left ventricular free wall thicknesses as well as an increased left ventricular fractional shortening (FS). 18 , 19 , 20 , 23 , 24 , 25 , 26 , 27 However, the influence of slight changes within the normal physiological range of HR on echocardiographic variables of cardiac function has not been investigated yet.…”

“… 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 Postexercise evaluation of cardiac variables and pharmacological stress testing demonstrated decreases in left ventricular dimensions with increases in interventricular septum and left ventricular free wall thicknesses as well as an increased left ventricular fractional shortening (FS). 18 , 19 , 20 , 23 , 24 , 25 , 26 , 27 However, the influence of slight changes within the normal physiological range of HR on echocardiographic variables of cardiac function has not been investigated yet. Heart rate and BP might vary during the echocardiographic exam as a result of stress because of an unknown environment.…”

Quantitative Analysis of Stress Echocardiograms in Healthy Horses with 2-Dimensional (2D) Echocardiography, Anatomical M-Mode, Tissue Doppler Imaging, and 2D Speckle Tracking

“…It has been achieved by manual tracking of endocardial motion and subjective evaluation of regional wall motion. 4,12,13 However, truly quantitative approaches have not been established in horses.…”

Equine echocardiography: Can dobutamine infusion correct alterations due to sedation with alpha-2 agonists?

“…To prevent the rapid heart rate decline post-exercise, pharmacological stress protocols have been developed [ 14 ]. Infusion of dobutamine provokes an increase in LV and IVS wall thickness and a decrease in LVID both in systole and diastole [ 9 , 11 ].…”