Left ventricular function in horses pertains to the performance of the left ventricle, a chamber of the heart responsible for pumping oxygenated blood to the body. This aspect of cardiac function is vital for maintaining circulatory efficiency and overall cardiovascular health in equines. Parameters such as stroke volume, cardiac output, and ejection fraction are commonly assessed to evaluate left ventricular function. Variations in these parameters can indicate underlying cardiac conditions or the impact of exercise and training on equine athletes. This page compiles peer-reviewed research studies and scholarly articles that explore the assessment, physiological mechanisms, and clinical implications of left ventricular function in horses.
Gehlen H, Fisch J, Merle R, Trachsel DS.Pituitary pars intermedia dysfunction (PPID), a neurodegenerative disease leading to reduced dopamine production, is a common disease in aged horses. The treatment is based on administration of the dopamine agonist pergolide. This drug has been related to valvular fibrosis in humans, but the cardiovascular effect of this drug has not yet been investigated in horses. Objective: To determine whether pergolide induces valvular disease in horses or affects the cardiac function. Methods: Standard, tissue Doppler (TDE) and two-dimensional speckle tracking (STE) echocardiography were performed in hor...
Decloedt A, Verheyen T, Sys S, De Clercq D, Bijnens B, van Loon G.The influence of atrioventricular (AV) interaction on mitral valve closure (MVC) and left ventricular (LV) isovolumic contraction is not fully clarified. We investigated the relationship among AV delay, MVC, and LV isovolumic contraction using a horse model because of the low heart rate and physiologically long AV delay. Results: Six horses were evaluated during sinus rhythm, right ventricular pacing without preceding atrial contraction, and dual-chamber pacing at AV delays of 150 to 350 ms, programmed at a constant rate. Right parasternal 4-chamber views were recorded for simultaneous measure...
Imhasly A, Tschudi PR, Lombard CW, Gerber V.The clinical and echocardiographic characteristics of 108 horses with echocardiographically confirmed mild mitral valve regurgitation (MR) were investigated along with its clinical progression. Follow-up consisted of a re-examination of 28 horses and questionnaires were used to obtain information on a further 43 cases. Thirty-seven horses with mild MR were lost to follow-up. Horses with mild MR were re-examined between 2 and 9 years (3.8+/-1.8 years) following first presentation, with mild MR still present and a small, but statistically significant (P=0.049) increase of left ventricular diamet...
Sandersen C, Detilleux J, Art T, Amory H.Stress echocardiography could be a useful diagnostic test in horses suspected to suffer from exercise-induced myocardial dysfunction as a cause of exercise intolerance. Objective: To evaluate the effect of treadmill exercise and pharmacological stress test on left ventricular echocardiographic parameters. Methods: Echocardiography was performed in 2 groups of 5 healthy horses, either immediately after a near-maximal treadmill exercise (Group EXE) or during a pharmacological challenge (Group DOB) consisting of 35 microg/kg atropine, followed by incremental dobutamine infusion rates of 2-6 micro...
Sandersen CF, Detilleux J, de Moffarts B, Van Loon G, Amory H.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 challen...
Gehlen H, Marnette S, Rohn K, Kreienbrock L, Stadler P.Echocardiographic measurements have to be reliable and reproducible with only a low day to day variability for detecting pathological changes of left ventricular myocardial function in horses. The day dependent fluctuation margin represents an important indicator for the reproducibility of a method. To find out the day to day variability of echocardiographic parameter in healthy warmblood horses, in the present study repeated echocardiographic measurements at three consecutive days were carried out (at the same time and by the same examiner) at 11 untrained and 7 trained warmblood horses. The ...
Young LE, Blissitt KJ, Clutton RE, Molony V.To evaluate the hemodynamic effects of a 60-minute infusion of dopexamine in horses anesthetized with halothane. Methods: 7 adult Thoroughbreds. Methods: Measurements of left ventricular function obtained by transesophageal Doppler echocardiography and cardiac catheterization. Results: Infusion of dopexamine (4 micrograms/kg of body weight/min) significantly increased heart rate, cardiac output, maximal rates of increase and decrease of left ventricular pressure, and maximal acceleration and maximal velocity of aortic blood flow. Left ventricular ejection time significantly increased, and pre-...
Young LE, Blissitt KJ, Clutton RE, Molony V, Darke PG.Transoesophageal Doppler echocardiography was performed in 7 Thoroughbred horses anaesthetised with halothane. The procedure was performed on 4 occasions under standard conditions. On one occasion dobutamine hydrochloride was infused at 4 micrograms/kg/min for 20 min. Recordings of aortic blood velocity, obtained using high pulsed repetition frequency Doppler echocardiography (HPRF), were used to derive maximum acceleration (dv/dtmax), maximum velocity (Vmax), left ventricular ejection time (ET), pre-ejection period (PEP), velocity time integral (VTI) and cardiac output (CO). The coefficient o...
Rugh KS, Garner HE, Sprouse RF, Hatfield DG.Systemic arterial hypertension is associated with equine laminitis, a disease precipitated by gross over-ingestion of carbohydrates. We examined the hearts from nine chronically hypertensive (161 +/- 11/99 +/- 6 mmHg) laminitic ponies and nine normotensive (128 +/- 2/76 +/- 3 mmHg) ponies postmortem for signs of left ventricular hypertrophy. The hypertensive ponies had hearts which were significantly larger (7.77 +/- 0.26 g/kg bodyweight (BW) vs. 5.67 +/- 0.22 g/kg BW), as well as increased combined left ventricle and septum weight (4.99 +/- 0.21 g/kg BW vs. 3.67 +/- 0.20 g/kg BW) and left ven...
O'Callaghan MW.This study was initiated to determine the accuracy of M-mode echocardiography in measuring left ventricular dimensions and estimating heart weights in horses. Left ventricular free wall and interventricular septal thickness and left ventricular external and internal diameters were measured and heart weights estimated from the echocardiograms of 47 horses. Autopsy measurements of the same parameters were then recorded. Statistical comparison of the data demonstrated: (1) Systolic measurements of wall thickness more closely resembled the heart in death than the diastolic measurements; (2) good c...
Rawlings CA, Bisgard GE, Dufek JH, Buss DD, Will JA, Birnbaum ML, Chopra PS, Kahn DR.Prolonged extracorporeal membrane oxygenation (PEMO) was performed in 6 adult ponies with the membrane oxygenator in vein-to-artery bypass circuit. A flow rate equal to 46 per cent of control cardiac output was diverted through the PEMO circuit of 10 to 24 hours. Three of the 6 ponies were perfused for at least 20 hours and developed no complications. Immediately following initiation of PEMO, left ventricular output decreased; however, in the interval between 6 and 24 hours, left ventricular output was increased above control levels. Aortic pressure and left ventricular work were markedly elev...
HOLT JP, RHODE EA, PEOPLES SA, KINES H.Studies of left ventricular volume and pressure have been carried out in the control state in four classes of intact anesthetized mammals (horses, cattle, swine, and dogs), body weights of which varied 54-fold. On the basis of these studies of both large and small hearts, extending over a wide range, a pattern of function for the left ventricle of all mammals has been described. Mathematical equations are given describing the interrelationships between left ventricular end-diastolic volume and end-systolic volume, stroke volume, cardiac output, stroke-work, heart rate, and total peripheral res...
HOLT JP, RHODE EA, PEOPLES SA, KINES H.Studies of left ventricular volume and pressure have been carried out in the control state in four classes of intact anesthetized mammals (horses, cattle, swine, and dogs), body weights of which varied 54-fold. On the basis of these studies of both large and small hearts, extending over a wide range, a pattern of function for the left ventricle of all mammals has been described. Mathematical equations are given describing the interrelationships between left ventricular end-diastolic volume and end-systolic volume, stroke volume, cardiac output, stroke-work, heart rate, and total peripheral res...
Sandersen C, Detilleux J, Art T, Amory H.Stress echocardiography could be a useful diagnostic test in horses suspected to suffer from exercise-induced myocardial dysfunction as a cause of exercise intolerance. Objective: To evaluate the effect of treadmill exercise and pharmacological stress test on left ventricular echocardiographic parameters. Methods: Echocardiography was performed in 2 groups of 5 healthy horses, either immediately after a near-maximal treadmill exercise (Group EXE) or during a pharmacological challenge (Group DOB) consisting of 35 microg/kg atropine, followed by incremental dobutamine infusion rates of 2-6 micro...
Rugh KS, Garner HE, Sprouse RF, Hatfield DG.Systemic arterial hypertension is associated with equine laminitis, a disease precipitated by gross over-ingestion of carbohydrates. We examined the hearts from nine chronically hypertensive (161 +/- 11/99 +/- 6 mmHg) laminitic ponies and nine normotensive (128 +/- 2/76 +/- 3 mmHg) ponies postmortem for signs of left ventricular hypertrophy. The hypertensive ponies had hearts which were significantly larger (7.77 +/- 0.26 g/kg bodyweight (BW) vs. 5.67 +/- 0.22 g/kg BW), as well as increased combined left ventricle and septum weight (4.99 +/- 0.21 g/kg BW vs. 3.67 +/- 0.20 g/kg BW) and left ven...
Imhasly A, Tschudi PR, Lombard CW, Gerber V.The clinical and echocardiographic characteristics of 108 horses with echocardiographically confirmed mild mitral valve regurgitation (MR) were investigated along with its clinical progression. Follow-up consisted of a re-examination of 28 horses and questionnaires were used to obtain information on a further 43 cases. Thirty-seven horses with mild MR were lost to follow-up. Horses with mild MR were re-examined between 2 and 9 years (3.8+/-1.8 years) following first presentation, with mild MR still present and a small, but statistically significant (P=0.049) increase of left ventricular diamet...
O'Callaghan MW.This study was initiated to determine the accuracy of M-mode echocardiography in measuring left ventricular dimensions and estimating heart weights in horses. Left ventricular free wall and interventricular septal thickness and left ventricular external and internal diameters were measured and heart weights estimated from the echocardiograms of 47 horses. Autopsy measurements of the same parameters were then recorded. Statistical comparison of the data demonstrated: (1) Systolic measurements of wall thickness more closely resembled the heart in death than the diastolic measurements; (2) good c...
Decloedt A, Verheyen T, Sys S, De Clercq D, Bijnens B, van Loon G.The influence of atrioventricular (AV) interaction on mitral valve closure (MVC) and left ventricular (LV) isovolumic contraction is not fully clarified. We investigated the relationship among AV delay, MVC, and LV isovolumic contraction using a horse model because of the low heart rate and physiologically long AV delay. Results: Six horses were evaluated during sinus rhythm, right ventricular pacing without preceding atrial contraction, and dual-chamber pacing at AV delays of 150 to 350 ms, programmed at a constant rate. Right parasternal 4-chamber views were recorded for simultaneous measure...
Gehlen H, Marnette S, Rohn K, Kreienbrock L, Stadler P.Echocardiographic measurements have to be reliable and reproducible with only a low day to day variability for detecting pathological changes of left ventricular myocardial function in horses. The day dependent fluctuation margin represents an important indicator for the reproducibility of a method. To find out the day to day variability of echocardiographic parameter in healthy warmblood horses, in the present study repeated echocardiographic measurements at three consecutive days were carried out (at the same time and by the same examiner) at 11 untrained and 7 trained warmblood horses. The ...
Rawlings CA, Bisgard GE, Dufek JH, Buss DD, Will JA, Birnbaum ML, Chopra PS, Kahn DR.Prolonged extracorporeal membrane oxygenation (PEMO) was performed in 6 adult ponies with the membrane oxygenator in vein-to-artery bypass circuit. A flow rate equal to 46 per cent of control cardiac output was diverted through the PEMO circuit of 10 to 24 hours. Three of the 6 ponies were perfused for at least 20 hours and developed no complications. Immediately following initiation of PEMO, left ventricular output decreased; however, in the interval between 6 and 24 hours, left ventricular output was increased above control levels. Aortic pressure and left ventricular work were markedly elev...
Young LE, Blissitt KJ, Clutton RE, Molony V.To evaluate the hemodynamic effects of a 60-minute infusion of dopexamine in horses anesthetized with halothane. Methods: 7 adult Thoroughbreds. Methods: Measurements of left ventricular function obtained by transesophageal Doppler echocardiography and cardiac catheterization. Results: Infusion of dopexamine (4 micrograms/kg of body weight/min) significantly increased heart rate, cardiac output, maximal rates of increase and decrease of left ventricular pressure, and maximal acceleration and maximal velocity of aortic blood flow. Left ventricular ejection time significantly increased, and pre-...
Gehlen H, Fisch J, Merle R, Trachsel DS.Pituitary pars intermedia dysfunction (PPID), a neurodegenerative disease leading to reduced dopamine production, is a common disease in aged horses. The treatment is based on administration of the dopamine agonist pergolide. This drug has been related to valvular fibrosis in humans, but the cardiovascular effect of this drug has not yet been investigated in horses. Objective: To determine whether pergolide induces valvular disease in horses or affects the cardiac function. Methods: Standard, tissue Doppler (TDE) and two-dimensional speckle tracking (STE) echocardiography were performed in hor...
Young LE, Blissitt KJ, Clutton RE, Molony V, Darke PG.Transoesophageal Doppler echocardiography was performed in 7 Thoroughbred horses anaesthetised with halothane. The procedure was performed on 4 occasions under standard conditions. On one occasion dobutamine hydrochloride was infused at 4 micrograms/kg/min for 20 min. Recordings of aortic blood velocity, obtained using high pulsed repetition frequency Doppler echocardiography (HPRF), were used to derive maximum acceleration (dv/dtmax), maximum velocity (Vmax), left ventricular ejection time (ET), pre-ejection period (PEP), velocity time integral (VTI) and cardiac output (CO). The coefficient o...
Sandersen CF, Detilleux J, de Moffarts B, Van Loon G, Amory H.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 challen...
