Diastole in horses refers to the phase of the cardiac cycle during which the heart muscle relaxes and allows the chambers to fill with blood. This process is essential for maintaining effective circulation and ensuring that oxygenated blood is delivered throughout the horse's body. During diastole, the atria and ventricles of the heart expand as they fill with blood, preparing for the subsequent contraction phase, or systole. Understanding diastolic function in horses is important for assessing cardiac health and diagnosing potential heart conditions. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, assessment methods, and clinical implications of diastolic function in equine cardiovascular health.
Reef VB, Spencer P.Echocardiographic evaluation of 23 horses with aortic insufficiency was performed, using M-mode (n = 23) and 2-dimensional real-time echocardiography (n = 14 of 23). Echocardiograms were evaluated for abnormalities of aortic and mitral valves and alterations in motion of these valves. Changes in left ventricular chamber size and function, as well as aortic root size, were evaluated. The presence of other cardiac disease was also evaluated. Horses with aortic insufficiency had significant increases (P less than 0.01) in mean values of left ventricular chamber size, aortic root diameter, and sho...
Wawrzeńska M.In this paper, the effect of ascorbic acid on motoric activity of the intestines of rabbits, pigs, cows, sheep and horses has been determined, and a possible participation of the adrenogenic system in this mechanism has been shown. In experiments in vitro the motility of the duodeum, jejunum, caecum and colon in the animals mentioned abowe was recorded by the method of Magnus after administration of ascorbic acid. Diastolic reactions were observed in all animals, which were much greater in small intestines than in large ones. To elucidate the diastolic mechanism under the influence of ascorbic...
Parry BW, Anderson GA.Seventeen horses were used to determine the variances associated with blood pressure cuff application (Sp2) and with other inherent errors (So2). Systolic pressure values had Sp2 = 3.9 mmHg and So2 = 5.6 mmHg, while diastolic pressure values had Sp2 = 1.1 mmHg and So2 = 4.4 mmHg. Thus, to be considered different, two blood pressure means (in mmHg), each derived from three readings, had to differ by at least 3.9 for systolic pressure and 3.4 for diastolic pressure when all readings were made without cuff displacement; 6.8 for systolic pressure and 4.6 for diastolic pressure when the cuff was re...
Miller PJ, Holmes JR.A method is described of processing transaortic valve pressures in the horse using the first derivative of the left ventricular pressure to define the beginning and end of each systolic complex. To determine the beginning of each systole three definitions of left ventricular end diastolic pressure (LVEDP), based on a 100, 150 or 200 mmHg/sec rate of left ventricular diastolic pressure rise, were evaluated. These definitions were also evaluated for their ability to determine isovolumic contraction time (ICT) and pulse interval. The best of these, LVEDP 150, was defined as the last point in dias...
Holmes JR, Miller PJ.The paper describes clinical observations in three horses with ruptured mitral valve chordae. Horses with ruptured mitral valve chordae may have a history of sudden onset of acute distress with predominantly respiratory symptoms. On auscultation there will be a widespread pansystolic murmur with an extension of the area of cardiac auscultation. The third heart sound may be very pronounced and unduly prolonged, associated with high volume flow during early ventricular filling in diastole. However, these sounds are not specific for chordal rupture--they are typical of severe mitral regurgitation...
Hamlin RL, Levesque MJ, Kittleson MD.Transmural myocardial blood flow was measured with microspheres in systole and in diastole, along with intramyocardial pressure, in seven anaesthetised horses. Intramyocardial pressures were measured with a miniature manometer implanted in the tip of a 16-gauge needle. Peak systolic intramyocardial pressure decreased from subendocardium to subepicardium and never exceeded intraventricular pressure. Systolic blood flow decreased from epicardium to endocardium where it did not differ from zero. Diastolic blood flow increased from epicardium to subendocardium, but then decreased in the most endoc...
Brown CM, Holmes JR.The paper describes observations on 8 horses at rest using catheter-mounted microtransducers to record intracavity pressures. In 5 of them records were obtained from both left and right sides and in 3 horses from the right heart only. Twelve indices were measured. Variations in left ventricular end-diastolic pressure seemed to influence the results on many of the parameters. It is suggested that left ventricular end-diastolic pressure itself may be a useful guide to left ventricular functional efficiency but more work is necessary to further evaluate these indices as possible measures of myoca...
Rumberger JA, Nerem RM, Muir WW.Measurements of the pressure waveform development and the wave transmission characteristics in the left extramural coronary arteries of the horse have been carried out. Near the ostium the left coronary pressure waveforms are seen to be virtually identical to the corresponding aortic root waveforms; however, the present of low frequency, relatively large amplitude pressure oscillations (on the order of 5 to 10 Hz) gradually become the dominant diastolic feature as one proceeds distally from the left ostium, and these eventually completely mask the incisura. In a limited number of experiments, ...
Brown CM, Holmes JR.The paper describes observations during individual cardiac cycles on the changing pressures and sounds recorded from the various chambers of the heart and aorta, related to phonocardiograms from an external microphone hand-held over the cardiac area. The majority of the first sound appears to arise from the left side of the heart after the AV valves have closed and the second sound is a consequence of sudden deceleration of blood against already closed semilunar valves. Systolic murmurs at the aortic root may be benign from increased flow and turbulence at the peak of ejection but these may no...
Vanselow B, McCarthy M, Gay CC.The occurrence and timing of heart sounds were examined from phonocardiograms taken from the mitral, aortic and tricupsid recording areas in each of 18 horses. 10 sound events could be identified with each cardiac cycle. Atrial contraction produced up to 3 sound events. The first heart sound consisted of 4 components whereas the second sound was single. Two sound events were associated with the 3rd heart sound in early diastole. The occurrence of third and fourth heart sound components varied between horses and between recording areas. The mitral recording area was considered most satisfactory...
Hörnicke H, von Engelhardt W, Ehrlein HJ.Carotid loops were prepared in 3 horses several months prior to the experiments. Systemic blood pressure was recorded at rest and during exercise by insertion of a plastic cannula into the carotid artery. The pressure transducer was fixed at the neck of the animal. The blood pressure signal was transmitted by telemetry. When the horses were standing under the rider, the following results were obtained: heart rate 38 +/- 5 beats-min-1, systolic pressure 115 +/- 15, disstolic pressure 83 +/- 10, mean pressure 97 +/- 12, and pulse pressure 32 +/- 9 mm Hg. During steady gallop at a mean speed of 5...
Pipers FS, Hamlin RL.Echocardiograms were obtained from 25 standing, clinically normal horses, using an ultrasonic recording device. The echobeam penetrated the right thoracic wall in the area of the 4th to 5th intercostal space, with a frequency of 2.5 mHz. Measurements of left ventricular wall thickness generated a mean value of 3.2 +/- 0.18 (SEM)cm, whereas the left ventricular chamber diameter in diastole was 9.3 +/- 0.30 cm and in systole was 5.7 +/- 0.23 cm. The aortic root dimensions had a mean of 7.7 cm, with a SEM of 0.16. Mitral valve closing slope (E-F) was calculated to be 17.7 +/- 0.87 mm/second, and ...
Gay CC, McCarthy M, Reynolds WT, Carter J.A method using the Doppler ultrasound principle for indirect determination of arterial blood pressure in the horse is described. The method is simple and suitable for field situations. Validation studies show that systolic and diastolic blood pressure measurements bear a close relationship to true values obtained by direct measurement.
Skarda RT, Muir WW, Milne DW, Gabel AA.Five healthy, mature, previously trained Standardbred horses were given no exercise (left in a stall) for 4 months, then jogged (slow exercise) for 3 weeks, and placed in a 6-week training period. Cardiac variables were measured at the beginning of training and after 14, 20, 35, and 42 days of training before and at 10, 15, 20, 25, and 30 minutes after a 1.8-km (in 3:12 +/- 2 seconds) standard, submaximal exercise test on a deep 0.53-km track. There was no significant change during the 6-week conditioning period in the following variables at rest or at any of the times observed during recovery...
Johnson JH, Garner HE, Hutcheson DP.Indirect systolic and diastolic arterial pressure measurements of 456 Thoroughbred horses of various ages and sex stabled at 9 different race tracks were measured with an ultrasonic-Doppler device interfaced with a sphygmomanometer cuff. The mean systolic pressure was 111.8 +/- 13.3 mmHg and the mean diastolic pressure was 69.6 +/- 13.8 mmHg in this population.
Holmes JR.The paper describes the spatial vector changes during ventricular depolarisation in 190 horses using a semi-orthogonal ECG lead system. The replacement of planar vector loops by a plot of 3 parameters to depict the changing spatial vector, with a time base on the X axis, is described and illustrated. Some horses with diastolic murmurs and some with a history of respiratory problems formed 2 distinct groups. As a result of these findings a possible relationship between the vector changes and the anatomical siting of the ventricles is suggested and discussed. Attention is drawn to certain measur...
Bishop SP, Cole CR, Smetzer DL.Twelve horses and 3 mules with grade II or louder prolonged diastolic murmurs were selected for functional and histopathologic study. Aortic insufficiency was demonstrated in all mules and in all except two horses on the basis of murmurs, jet lesions and/or pathologic and incompetent valve cusps. In 15 control animals lesions resulting in aortic insufficiency were not found.
A thick fibrous band was present on all aortic valve cusps judged to be definitely insufficient. This band occurred at the line of valvular closure, parallel to the free edge, and allowed eversion of the peripheral portio...
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...
Pipers FS, Hamlin RL.Echocardiograms were obtained from 25 standing, clinically normal horses, using an ultrasonic recording device. The echobeam penetrated the right thoracic wall in the area of the 4th to 5th intercostal space, with a frequency of 2.5 mHz. Measurements of left ventricular wall thickness generated a mean value of 3.2 +/- 0.18 (SEM)cm, whereas the left ventricular chamber diameter in diastole was 9.3 +/- 0.30 cm and in systole was 5.7 +/- 0.23 cm. The aortic root dimensions had a mean of 7.7 cm, with a SEM of 0.16. Mitral valve closing slope (E-F) was calculated to be 17.7 +/- 0.87 mm/second, and ...
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 ...
Hiraga A, Hobo S, Birks EK, Takahashi T, Hada T, Smith BL, Carr EA, Pascoe JR, Jones JH.Three mature Thoroughbred horses were prepared surgically with ultrasonic sonomicrometer crystals affixed to their ventricular pericardia. Signals from crystals recorded dimensions of axes across the left ventricle. Cubic algorithms were fitted to dimensional data to generate volume estimates that matched stroke volumes simultaneously measured using the Fick principle. As horses stood at rest or exercised at various intensities (approx 7, 12, 24, 47 and 100% maximal rate of O2 consumption VO2max[), left ventricular dimensions were recorded and 20 consecutive diastolic and systolic volumes calc...
Holmes JR, Miller PJ.The paper describes clinical observations in three horses with ruptured mitral valve chordae. Horses with ruptured mitral valve chordae may have a history of sudden onset of acute distress with predominantly respiratory symptoms. On auscultation there will be a widespread pansystolic murmur with an extension of the area of cardiac auscultation. The third heart sound may be very pronounced and unduly prolonged, associated with high volume flow during early ventricular filling in diastole. However, these sounds are not specific for chordal rupture--they are typical of severe mitral regurgitation...
Santos MM, Ramos GV, de Figueiredo IM, Silva TCBV, Lacerda-Neto JC.Cardiac adaptation to conditioning in horses was evaluated after empirical training based on trainers' experience. Twelve purebred Arabian horses, aged (mean ± SD) 28.42 ± 3.75 months, which did not perform any type of exercise prior to the research, were submitted to treadmill conditioning for six weeks. The conditioning program was based on the velocity run by the horse at which the blood lactate concentration, determined in an incremental exercise test (IET), reached 2 mmol/L (V). The velocity at which the blood lactate concentration reached 4 mmol/L (V) was also determined. The echocardi...
Parry BW, Anderson GA.Seventeen horses were used to determine the variances associated with blood pressure cuff application (Sp2) and with other inherent errors (So2). Systolic pressure values had Sp2 = 3.9 mmHg and So2 = 5.6 mmHg, while diastolic pressure values had Sp2 = 1.1 mmHg and So2 = 4.4 mmHg. Thus, to be considered different, two blood pressure means (in mmHg), each derived from three readings, had to differ by at least 3.9 for systolic pressure and 3.4 for diastolic pressure when all readings were made without cuff displacement; 6.8 for systolic pressure and 4.6 for diastolic pressure when the cuff was re...
Johnson JH, Garner HE, Hutcheson DP.Indirect systolic and diastolic arterial pressure measurements of 456 Thoroughbred horses of various ages and sex stabled at 9 different race tracks were measured with an ultrasonic-Doppler device interfaced with a sphygmomanometer cuff. The mean systolic pressure was 111.8 +/- 13.3 mmHg and the mean diastolic pressure was 69.6 +/- 13.8 mmHg in this population.
Vanselow B, McCarthy M, Gay CC.The occurrence and timing of heart sounds were examined from phonocardiograms taken from the mitral, aortic and tricupsid recording areas in each of 18 horses. 10 sound events could be identified with each cardiac cycle. Atrial contraction produced up to 3 sound events. The first heart sound consisted of 4 components whereas the second sound was single. Two sound events were associated with the 3rd heart sound in early diastole. The occurrence of third and fourth heart sound components varied between horses and between recording areas. The mitral recording area was considered most satisfactory...
Brown CM, Holmes JR.The paper describes observations on 8 horses at rest using catheter-mounted microtransducers to record intracavity pressures. In 5 of them records were obtained from both left and right sides and in 3 horses from the right heart only. Twelve indices were measured. Variations in left ventricular end-diastolic pressure seemed to influence the results on many of the parameters. It is suggested that left ventricular end-diastolic pressure itself may be a useful guide to left ventricular functional efficiency but more work is necessary to further evaluate these indices as possible measures of myoca...
Brown CM, Holmes JR.The paper describes observations during individual cardiac cycles on the changing pressures and sounds recorded from the various chambers of the heart and aorta, related to phonocardiograms from an external microphone hand-held over the cardiac area. The majority of the first sound appears to arise from the left side of the heart after the AV valves have closed and the second sound is a consequence of sudden deceleration of blood against already closed semilunar valves. Systolic murmurs at the aortic root may be benign from increased flow and turbulence at the peak of ejection but these may no...
Sepulveda MF, Perkins JD, Bowen IM, Marr CM.Doppler tissue imaging (DTI) is a novel noninvasive method by which myocardial velocity can be assessed directly and it allows regional, rather than global, cardiac function to be evaluated. Objective: That regional differences in myocardial velocities exist within the equine ventricle. Objective: To develop a repeatable examination technique for DTI in horses, describe DTI findings in various regions of the normal equine ventricle, compare colour (CDTI) and spectral (SDTI) techniques of DTI, and document regional differences in myocardial velocity. Methods: Five regions of the ventricles (rig...
Langsetmo I, Weigle GE, Erickson HH, Fedde MR.Exercising horses have extremely high right and left atrial pressures. Limitation in ventricular function (i.e. relaxation) may play a role in these high pressures. We studied relaxation characteristics of the right ventricular myocardium and the impact of frusemide (2.0 mg/kg bwt i.v.) on these characteristics in horses exercising at 8, 10, 12 and 14 m/s. Exercise tests were performed 4 h after administration of frusemide. Right ventricular (RV) pressure was analysed using Fast Fourier Transform techniques to remove non cardiac components of the pressure signal. Mean right atrial (RA) pressur...
Wawrzeńska M.In this paper, the effect of ascorbic acid on motoric activity of the intestines of rabbits, pigs, cows, sheep and horses has been determined, and a possible participation of the adrenogenic system in this mechanism has been shown. In experiments in vitro the motility of the duodeum, jejunum, caecum and colon in the animals mentioned abowe was recorded by the method of Magnus after administration of ascorbic acid. Diastolic reactions were observed in all animals, which were much greater in small intestines than in large ones. To elucidate the diastolic mechanism under the influence of ascorbic...
Marr CM, Bright JM, Marlin DJ, Harris PA, Roberts CA.We hypothesised that exercise in a hot and humid environment would affect echocardiographic indices of cardiac dimensions and function more than exercise in a cool environment. M-mode echocardiograms were obtained in 5 clinically normal horses before, and at 0, 10, 30 and 60 min after a treadmill exercise test. The test was performed in a controlled environment at 20 degrees C/40% relative humidity (RH) and again at 30 degrees C/80% RH. All the horses completed the exercise test in cool conditions, but only one horse completed the exercise test in the hot/humid environment. The relaxation time...
Tavanaeimanesh H, Dezfouli MR, Vajhi A, Rostam A, Akbarinejad V, Sadeghian Chaleshtori S, Corley KT.The cardiovascular effects and duration of action of hypertonic saline are not yet fully understood in the horse. Objective: To determine the effects of hypertonic saline on cardiac measurements derived from echocardiography over a period of 90 min after infusion in euvolaemic and healthy horses. Methods: Experimental study. Methods: Five healthy conscious euvolaemic horses were infused with 5 ml/kg bwt hypertonic saline via a jugular catheter over 1 h. Immediately prior to infusion and at 0, 20, 40, 60 and 90 min after the completion of the infusion, echocardiographic images were obtained fro...
Miller PJ, Holmes JR.A method is described of processing transaortic valve pressures in the horse using the first derivative of the left ventricular pressure to define the beginning and end of each systolic complex. To determine the beginning of each systole three definitions of left ventricular end diastolic pressure (LVEDP), based on a 100, 150 or 200 mmHg/sec rate of left ventricular diastolic pressure rise, were evaluated. These definitions were also evaluated for their ability to determine isovolumic contraction time (ICT) and pulse interval. The best of these, LVEDP 150, was defined as the last point in dias...
Stadler P, Rewel A, Deegen E.Heart structures of 45 warmblooded horses were measured by M-mode-echocardiography. The current training level of 15 dressage horses (group I) and 15 show-jumping horses (group II) was category "S". In the third group were 15 untrained horses. Four standardized transducer positions were determined for the m-mode echobeam, calibrated according to the two-dimensional real time technique. End systolic and end diastolic diameters of left ventricle, right ventricle, aortic root, interventricular septum and left ventricular wall, as well as motion pattern of heart wall, mitral valve and aortic valve...
Chompoosan C, Pongthaisong P, Kenchaiwong W, Pontaema T, Lerdweeraphon W.Pregnancy affects maternal hemodynamics. The changes in autonomic nervous system activity for hemodynamics adaptation in pregnant horses are still unclear. Thus, this study aimed to examine the effect of pregnancy on electrocardiographic, vasovagal tonus index, and echocardiographic variables in horses. Unassigned: A total of 23 Thai native crossbred mares without any cardiac abnormalities were included in this study. The animals were assigned into two groups, a non-pregnant mare group (n =12) and a pregnant mare group (n = 11). Electrocardiogram recordings (paper speed = 25 mm/s and calibrati...
