Topic:Aorta
The aorta is the main artery in horses, responsible for transporting oxygenated blood from the left ventricle of the heart to the rest of the body. It is a large, elastic blood vessel that withstands high pressure and plays a vital role in the circulatory system. The structure and function of the equine aorta can be affected by various conditions, including aneurysms, rupture, and degenerative changes, which may impact a horse's health and performance. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, pathologies, and clinical implications of aortic health in horses.
Tracheobronchial perfusion during exercise in ponies. Tracheobronchial circulation during exercise has previously not been examined. Therefore blood flow to the trachea and bronchi (up to 7th generation of branching) was studied in seven healthy adult ponies at rest and during the 3rd and 10th min of exercise performed at a treadmill speed setting of 25 km/h. The ambient air temperature varied from 19 to 20 degrees C and humidity from 35 to 45%. To determine blood flow radionuclide-labeled 15-microns-diameter microspheres were injected into the left ventricle via a catheter advanced from the left carotid artery (exposed using local anesthesia), a...
Technique for transrectal ultrasonography of the cranial mesenteric artery of the horse. Transrectal ultrasonography was successfully used to image the cranial mesenteric artery and its branches in 23 adult horses. The artery could be imaged from its origin at the aorta distally to identify several bifurcations. The method for transrectal imaging of the cranial mesenteric artery and its major branches required 3 distinct transducer positions. One position was used to locate the cranial mesenteric artery by imaging the caudal portion of the aorta from the aortic bifurcation cranially to the level of the cranial mesenteric artery. The second position was used to image the origin of ...
Morphological changes of the aorta and pulmonary artery in thoroughbred racehorses. The aorta and extrapulmonary artery were examined pathologically in 33 thoroughbred racehorses ranging in age from 1 to 5 years. Many of the great vessels of these horses exhibited degenerative or sclerotic changes in the media with neither lipidosis nor deposits of cholesterol. The severe lesions were predominantly observed at the bifurcation of the pulmonary artery. The severity of the lesions in both the aorta and pulmonary artery appeared to be associated with the racing career of the racehorse rather than with increasing age. Histopathogenetically, the medial changes in the great vessels ...
Atresia of the right atrioventricular orifice with complete transposition of the great arteries in a horse. The heart of a 6-week old Arabian filly with a history of poor health and exercise intolerance revealed at postmortem examination, multiple cardiac malformations which included atresia of the right atrioventricular orifice (tricuspid atresia, with associated atrial and ventricular septal defects), complete transposition of the great arteries, anomalous drainage of the venae cavae and coronary sinus into the left atrium, coarctation of the aorta, and a small but patent ductus arteriosus. The course of blood through the heart was suggested and discussed.
Transrectal ultrasonography of the caudal portion of abdominal and pelvic cavities in horses. A 5-MHz transducer was used transrectally to image palpable structures in the caudal portion of abdominal and pelvic cavities of 12 horses. In 8 healthy horses, structures scanned transrectally included the left kidney, spleen, urinary bladder, urethra, accessory sex organs in the male, portions of the intestinal tract, caudal portion of the aorta, and iliac arteries, and, in small horses, the cranial mesenteric artery. The transrectal technique was used to evaluate these structures in 4 horses with clinical signs indicating intrapelvic or intra-abdominal disease. Seemingly, transrectal ultras...
Pulsed-wave Doppler evaluation of intracardiac blood flow in 30 clinically normal Standardbred horses. Pulsed-wave Doppler echocardiography was performed on 30 clinically normal 1- to 6-year-old racing Standardbreds. There were 13 females, 13 geldings, and 4 stallions. Cardiac disease was not detected with M-mode, 2-dimensional real-time or pulsed-wave Doppler echocardiography. Normal flow velocities for right and left atrial outflow, right and left ventricular outflow, the aorta, and pulmonary artery were determined. Peak flow velocities for right and left atrial outflow occurred during the rapid filling phase and were higher toward the mitral valve (mean, 0.70 +/- 0.24 m/s) than toward the tr...
Epidermal growth factor-mediated effects on equine vascular smooth muscle cells. Epidermal growth factor (EGF) receptor binding kinetics and EGF-mediated stimulation of DNA synthesis and cellular proliferation were studied in cultured vascular smooth muscle cells (VSMC) from the equine thoracic aorta. Binding studies, using murine 125I-labeled EGF, indicate the presence of a single class of high-affinity binding sites (apparent KD = 2.8 X 10(-11) M), with an estimated maximal binding capacity of 5,800 sites/cell. EGF stimulated [3H]thymidine uptake in confluent quiescent monolayers in a dose-dependent fashion, half-maximal stimulation occurring at 7.5 X 10(-11) M. Likewise...
Left ventricular oxygen extraction during submaximal and maximal exertion in ponies. 1. Left ventricular (LV) myocardial O2 extraction was studied in five healthy ponies which had catheters implanted in the great cardiac vein and main pulmonary artery 15-30 days before the study. The abdominal aorta was percutaneously catheterized to sample arterial blood. 2. In addition, phasic LV and aortic pressures, LV dP/dtmax and rate-pressure product were also studied; dP/dtmax is the maximal rate of rise of the left ventricular pressure during the isovolumic phase, and is considered an index of myocardial contractility. Measurements were made at rest (control) and during adenosine infu...
Experimentally induced cartilaginous fractures (osteochondritis dissecans) in foals fed low-copper diets. Four Thoroughbred foals were weaned from their dams when they were 1 day old and were fed a liquid milk-replacer diet containing approximately 1.7 micrograms of copper/g from plastic buckets for 4 to 7 months. They were kept in stalls with fiberglass walls and asphalt floors covered with rubber pads. Serum copper and zinc concentrations were determined 3 times/week by atomic absorption spectrophotometry, and liver copper and zinc concentrations were determined similarly after acid digestion of tissues taken at necropsy. The amount of soluble collagen in articular cartilage and aortic tissue wa...
Aortic valve insufficiency in a one-year-old colt. Aortic insufficiency was suspected in a thin 1-year-old colt with a grade IV/V decrescendo holodiastolic murmur and a bounding arterial pulse. Echocardiographic findings (diastolic fluttering of the septal leaflet of the mitral valve, left ventricular volume overload, and incomplete aortic valve closure) were diagnostic for aortic valve insufficiency. Moderately thick fibrotic aortic valve leaflets were found at necropsy. Fenestrations were found in the aortic and pulmonic valve cusps. Congenital valvular disease may have led to aortic valvular insufficiency in this horse.
Echocardiographic evaluation of equine aortic insufficiency. 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...
Use of ultrasonography for the detection of aortic-iliac thrombosis in horses. Two dimensional ultrasonographic evaluation of the iliac arteries and terminal portion of the aorta was utilized in 18 horses with histories of exercise intolerance or hindlimb lameness. A plaque or thrombus was imaged in one or more of these vessels in 5 horses. In 2 horses, the initial rectal examination findings were normal and the thrombus may have been missed without the use of diagnostic ultrasonography.
Systemic and pulmonary haemodynamics in normal neonatal foals. Cardiopulmonary function was studied in 10 full-term healthy foals from birth to 14 days of age. Systemic and pulmonary haemodynamics were recorded in lateral recumbency via indwelling aortic and pulmonary artery catheters. Mean body weight increased from 45.4 +/- 2.4 kg on Day 1 to 70.6 +/- 6.1 kg on Day 14. All foals had a continuous murmur of patent ductus arteriosus for 3-6 days. From Day 1 (12 h old) to Day 14, heart rate increased (89 +/- 4 to 95 +/- 5/min), mean aortic pressure increased (87.7 +/- 1.9 to 100.3 +/- 3.2 mmHg), mean pulmonary artery pressure decreased (38.6 +/- 4.6 to 27.4...
Rupture of an aortic sinus aneurysm in a 15-year-old broodmare. A 15-year-old, Standardbred broodmare with an aortic sinus aneurysm developed rupture of the aneurysm with subsequent rupture of a tricuspid valve chorda tendinae, tricuspid regurgitation, acute right-sided congestive heart failure, and pulmonary thromboembolism. Shunting of blood from the aorta through the ruptured aneurysm into the right ventricle resulted in decreased renal perfusion and acute renal failure. Initially, treatment of the mare with analgesics, fluids, and digoxin resulted in clinical improvement, but the mare's condition deteriorated after 8 days and the mare was euthanatized ...
Effect of furosemide administration on systemic circulation of ponies during severe exercise. Systemic distribution of blood flow was studied in 11 healthy adult grade ponies, using radionuclide-labeled microspheres (15 micron diameter) that were injected into the left ventricle. Measurements were made at rest, during severe exercise (SE) without furosemide, as well as during SE at 10 minutes and 120 minutes after furosemide administration (1.0 mg/kg, IV). During SE, heart rate, cardiac output, mean aortic pressure, and whole body O2 consumption were 220 +/- 4 beats/min, 720 +/- 44 ml/min/kg, 169 +/- 4 mm of Hg, and 126 +/- 9 ml of O2/min/kg, respectively. With SE performed after furos...
Vasodilator reserve in respiratory muscles during maximal exertion in ponies. Eight healthy adult grade ponies were studied at rest as well as during maximal exertion carried out with and without adenosine infusion (3 microM X kg-1 X min-1 into the pulmonary artery) on a treadmill to compare levels of blood flow in respiratory muscles with those in other vigorously working muscles and to ascertain whether there remained any unutilized vasodilator reserve in respiratory muscles of maximally exercising ponies. Radionuclide-labeled 15-micron-diam microspheres, injected into the left ventricle, were used to study tissue blood flows. During maximal exertion, there were incre...
Equine endothelial cells in vitro. Certain in vitro culture conditions were determined for equine endothelial cells obtained from the aorta and pulmonary arteries. Cells were enzymatically isolated from the vessel lumen, using clostridial collagenase (2.5 mg/ml of Hanks's balanced salt solution) incubated at 37 C for 30 minutes. Cells were cultured in alpha minimum essential medium supplemented with plasma-derived and nonplasma-derived bovine fetal sera, endothelial cell-growth supplement, heparin, and antibiotics. Smooth muscle cell growth was not inhibited with nonplasma-derived animal sera, plasma-derived equine serum, or he...
Cerebral, renal, adrenal, intestinal, and pancreatic circulation in conscious ponies and during 1.0, 1.5, and 2.0 minimal alveolar concentrations of halothane-O2 anesthesia. Blood flow to the brain, kidneys, adrenal glands, pancreas, and small intestine was studied in 8 healthy ponies while awake (control) and during 1.0, 1.5, and 2.0 minimal alveolar concentrations (MAC) of anesthesia produced, using halothane vaporized in oxygen. During the anesthesia steps, intermittent positive-pressure ventilation was used to ensure isocapnia. Organ blood flow was determined with 15-micron (diameter) radionuclide-labeled microspheres, after allowing 30 minutes of equilibration at each of the 3 preestablished end-tidal halothane concentrations. The sequence of 1.0, 1.5, and 2....
Ultrasonographic diagnosis of aorto-iliac thrombosis. A linear array 5 mHz ultrasonic scanner was used to diagnose aorto-iliac thrombosis in a 3 year old Standardbred gelding. There are no reports in the literature of utilization of ultrasonography for visualization of an aortic thrombus. The technique is fairly non-invasive, requiring only a rectal examination with a linear array probe. Arteriography is the only other method described for actual visualization of a thrombus. This procedure is technically difficult and highly invasive.
Enhanced prostacyclin biosynthesis and decreased thromboxane formation by 3-dimethylamino 5-(2′,6′-dichlorobenzylidene) 6-methyl (4H)-pyridazine (PC 89). The effects of 3-dimethylamino 5-(2',6'-dichlorobenzylidene) 6-methyl (4H)-pyridazine (PC 89) on the biosynthesis of PG I2 and TX A2 using horse aorta and horse platelet microsomes as sources of enzymes and arachidonic acid as substrate, were investigated. PC 89 (1.10(-6) M- 1.10(-3) M) dose-dependently - enhanced the biosynthesis of PG I2: the AD50 was 6.8 X 10(-6) M +/- 1.2 X 10(-9) M, the Vmax did not vary significantly with concentrations: PC 89 increased the affinity of enzyme for substrate - but inhibited TX A2 biosynthesis (ID50 = 3.31 X 10(-3) M +/- 4.8 X 10(-7) M): this inhibiting act...
Necrosis and rupture of the aorta and pulmonary trunk in four horses. Four horses are described with rupture of the aortic arch and pulmonary trunk which resulted in a fistula between these vessels. Ruptures were located near the ligamentum arteriosum. Histological examination of the vessel walls revealed media necrosis which was probably due to intimal thickening and/or medial fibrosis of the vasa vasorum.
[Thrombectomy of the descending aorta in the horse]. Thrombosis of the aorta as the cause of intermittent claudication in the horse appears to be rare. Two cases out of about 10 000 horses 1973-1984 are discussed. There are various views on its aetiology, whereby haemodynamic factors and disturbances of coagulation have been mentioned as well as parasites. For treatment surgical methods should be explored in addition to medical procedures. History, diagnosis and the attempt of an aortic thrombectomy in a 12 year old thoroughbred mare are described in this paper. A standardbred stallion was left untreated on owners wish.
Hypoplastic left ventricular syndrome in a foal. A necropsy diagnosis of hypoplastic left ventricular syndrome was made in a day-old foal. The cardiac abnormalities included mitral and aortic valve atresia, patent ductus arteriosus, and a secundum atrial septal defect. The left ventricle was hypoplastic and nonfunctional. The brief survival of the foal was a consequence of left-to-right shunting through the atrial septal defect and right-to-left shunting through the patent ductus. The information is presented to demonstrate the existence of the syndrome as a congenital defect in the horse and to clarify the necropsy findings for the practiti...
Neuroaxonal dystrophy of the accessory cuneate nucleus in horses. Data were collected from 37 horses with a neurologic disability and compared to a group of 34 normal horses. Affected horses had neuroaxonal dystrophy, gliosis, vacuoles, and sometimes pigment localized to the accessory cuneate nuclei with minimal or no changes in the spinal cord and no changes in the proximal peripheral nerves. The focal nature of the change and usual absence of significant light microscopic spinal cord or peripheral nerve changes are different than previously described equine neuropathologic conditions.
Relationships of left side systolic time intervals to beat-by-beat heart rate and blood pressure variables in some cardiac arrhythmias of the horse. Systolic time intervals (STIs), isovolumic contraction time (ICT) and left ventricular ejection time (LVET) were recorded from seven horses with supraventricular arrhythmia. The STIs were measured over a number of beats (33 to 100) directly from the left ventricular (LV) and aortic (Ao) pressure contours which were recorded simultaneously using two catheter-mounted transducers. ICT was significantly (P less than 0.01) and directly related to beat-by-beat heart rate (HR = 60/pulse interval) and LVET was significantly (P less than 0.01) and inversely related to heart rate in each of five horses....
Computer processing of transaortic valve blood pressures in the horse using the first derivative of the left ventricular pressure trace. 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...
Method of selective and non-selective angiocardiography for the horse. A practical and safe method of angiocardiography for the horse is described. The technique involved the rapid injection of 50 to 150 ml contrast agent via catheters in the right and left heart, pulmonary artery and aorta. The examination was carried out with the horse in the standing position or under general anaesthesia. Angiocardiograms were performed on 10 normal horses and satisfactory pictures of the right and left ventricles, pulmonary arteries, aorta and coronary circulation were obtained. The technique was also used in a foal with severe congenital heart disease. The most practical met...
Distribution of blood flow during moderate and strenuous exercise in ponies (Equus caballus). Blood flow to the brain, heart, kidneys, diaphragm, and skeletal muscles was studied at rest and during graded treadmill exercise, using radionuclide-labeled microspheres (15 microns diameter), in 11 healthy adult ponies. Hemodynamic changes brought about by exercise included marked increases in cardiac output, mean aortic pressure, left ventricular end-diastolic pressure, and right ventricular systolic and end-diastolic pressures. Blood flow to the brain stem and cerebral hemispheres was unchanged during both moderate exercise (heart rate = 154 +/- 3 beats/min) and severe exercise (heart rate...