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.
Miller PJ, Holmes JR.Transaortic blood pressures were recorded in seven horses using catheter mounted transducers during various types of supraventricular arrhythmia. Changes in left ventricular (LV) and aortic (Ao) pulse contours were associated with variation in pulse interval (PI). When PI lengthened there was a rise in LV end diastolic pressure (LVEDP) associated with a prolonged filling time. In contrast, a long PI resulted in a reduced end diastolic Ao pressure (AoEDP) due to a prolonged arterial 'run off'. LVdP/dt max representing the peak rate of rise of pressure during the isovolumic contraction period wa...
Parks C, Manohar M, Lundeen G.To examine the effects of tachycardia on coronary circulation, transmural distribution of myocardial blood flow (MBF, 15-micron diameter radionuclide-labeled microspheres) was studied in six healthy adult ponies at rest (heart rate = 60 +/- 7 beats . min-1), during ventricular pacing at 150 and 200 beats . min-1, as well as with ventricular pacing at 250 beats . min-1 before and during maximal coronary vasodilatation (iv adenosine infusion; 4 mumole . kg-1 . min-1). Mean aortic pressure and cardiac output were unchanged from control values with ventricular pacing. Whereas ventricular pacing at...
Parks CM, Manohar M.Transmural distribution of myocardial blood flow and coronary vasodilator reserve (15-microns-diam radionuclide-labeled microspheres) was studied in 11 adult, healthy ponies at rest and during moderate and severe exercise performed on a treadmill (heart rate 56 +/- 4, 154 +/- 3, and 225 +/- 7 beats . min-1, respectively.). Exercise resulted in a marked increase in cardiac output, mean aortic pressure, right ventricular (RV) systolic and end-diastolic pressure, left ventricular (LV) end-diastolic pressure, and the maximum rate of rise of LV pressure LV (dP/dtmax). Accompanying these changes was...
Bonagura JD, Pipers FS.A horse, a cow, and a dog with aortic valve vegetative endocarditis were studied by M-mode echocardiography. Echocardiographic abnormalities of the aortic valve, mitral valve, and left ventricle were observed. These features were identical to those reported in human beings with aortic valve endocarditis. Abnormalities associated with aortic valve endocarditis included irregular thickening of the valve, multiple linear echoes in the aortic root, diastolic prolapse of the aortic vegetation, and diastolic fluttering of a torn aortic valve. Some of these features were found in each animal. The con...
Katano Y, Imai S.The effects of dipyridamole on thromboxane A2 formation by horse platelet microsomes were studied in comparison with those of imidazole, a prototype inhibitor of TXA2 synthetase and nifedipine, a calcium antagonistic vasodilator. Thromboxane A2 was synthesized by incubating PGH2 with horse platelet microsomes and was assayed on the superfused rabbit aorta. Dipyridamole induced as strong an inhibition of TXA2 synthesis as imidazole, while nifedipine was without effects. The possible beneficial clinical outcomes of this effect of dipyridamole are discussed.
Jantosovicová J, Jantosovic J.To study the vascularization of the testis of stallions we used 96 testes. We examined its topography and anatomy by roentgenography, stereoroentgenography, by the corosive method, and by means of gel and China ink injections. To make the roentgeno-arteriograms we used minimum emulsified in glycerine as contrast medium. The branching off of the Aa. testiculares from the Aorta abdominalis is variable in stallions. We observed also a peculiar age-dependent arrangement of the loops of the convolution. In the adult stallion, the shape of the convolution is either cylindrical or conical, spindle-sh...
Vitums A, Bayly WM.Three Arabian males foals were presented with cyanosis, heart murmur, and exercise intolerance, Results of clinical evaluation suggested a tentative diagnosis of ventricular septal defect in conjunction with malformations of the great arteries. Each foal had a poor prognosis and was killed at the owners' requests. At necropsy, the malformed hearts of the three foals were virtually identical. Each heart had a large defect in the upper interventricular septum. The aorta originated from the hypertrophied right ventricle and partially overrode the ventricular septal defect. The aortic ostium was g...
Cranley JJ, McCullagh KG.The hearts and aortas of 2076 unselected horses of all ages were examined immediately after slaughter. Focal zones of fibrosis, observed in the myocardium of 14.3 per cent of hearts examined, were found in both atria and ventricles and were unrelated to age. Microscopically the majority of lesions involved myocardial fibre lysis and replacement fibrosis, although acute infarction was present in some cases. Intramyocardial arterioles in or adjacent to the lesions exhibited occlusive arteriosclerotic changes whereas those elsewhere remained patent. The evidence strongly suggests that the myocard...
Bisgard GE, Forster HV, Klein JP.Resting ventilation (PaCO2) and ventilatory responses to acute hypoxia and to intravenous NaCN were assessed over a 4-yr period following cutting of the carotid sinus nerves and stripping the adventitia of the aortic arch. The data indicated essentially complete loss of peripheral chemoreceptor function immediately after surgery and hypoventilation during normoxia (delta PaCO2 = +8.7 Torr). There was a time-dependent, partial recovery of peripheral chemoreceptor function between 2 and 22 mo after surgery. Approximately 10% of the ventilatory response to iv NaCN returned, and 30-40% of the norm...
Waugh SL, Campbell KB, Klavano PA, Grant BD.A surgical thoracotomy and implantation of an electromagnetic flow probe around the ascending aorta and catheters in the left ventricular (LV) apex of the horse were evaluated. Sixteen operations were done: 4 horses were used for acute experiments, 4 horses died from surgical manipulation, and 8 horses were studied chronically for 18 to 57 days. The electromagnetic flow probe allowed continuous measurement of stroke volume and heart rate. The LV apical catheters, in conjunction with thermal dilution techniques and pressure-sensitive devices, allowed measurement and calculation of mean arterial...
Waugh SL, Fregin GF, Thomas DP, Gerber N, Grant BD, Campbell KB.Aortic root blood flow was measured with an electromagnetic (EM) flow meter in unanesthetized horses during rest and exercise. The cardiac output response to exercise, as determined by the EM technique, was compared with the response reported by others who used indicator dilution techniques with good agreement. The EM method will allow making measurement of cardiovascular responses to exercise in the horse, not obtainable with other techniques.
van der Linde-Sipman JS, Goedegebuure SA, Kroneman J.In this article a description is given of the clinical and postmortem findings of a persistent right aortic arch in association with a persistent left ductus arteriosus and a ventricular septal defect in a horse.
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...
Brown CM, Holmes JR.Using microtransducers, the intracardiac phonocardiogram was recorded in 8 horses from the right heart and in 6 of them also on the left side. All 4 heart sounds were recorded but not in all sites. Their timing was related to pressure events. Systolic ejection murmurs were recorded in both the pulmonary artery and the aorta. Diastolic murmurs were recorded in 2 horses with aortic regurgitation, with maximum amplitude in the left ventricle. The findings were similar to those reported in man and agree with some of the recent concepts on heart sound production.
Brown CM, Holmes JR.The paper reports the changing pressure values during the cardiac cycle recorded from various chambers of the heart and great vessels using 2 catheter-mounted transducers, 9 cm apart. Pulse pressures are calculated. Transvalval pressure differences are determined taking account of the effect of hydrostatic pressure between the 2 sensors. The effects of some valvular lesions and arrhythmias and of changes in intrathoracic pressure are also described.
Brown CM, Holmes JR.Using a catheter with 2 transducers, one mounted at the tip and one 9 cm proximal to it, enabled transvalval pressure waveforms to be recorded in 8 horses. A simultaneous electrocardiogram acted as a time base. The changing waveforms produced in the chambers of the heart and great vessels are described and related to the events of the cardiac cycle. The effect of second degree AV block, ectopic beats, a pan diastolic murmur and chronic obstructive pulmonary disease are described.
Scott EA, Chaffee A, Eyster GE, Kneller SK.Two foals with a history of normalcy at birth developed a lack of exercise tolerance and weakness in the first few days of life. Weakness, inability to rise, and reluctance to suckle were common complaints. Physical examination of both foals revealed a cardiovascular abnormality, with a loud systolic murmur audible over both thoracic walls. Additional diagnostic techniques were blood gas analysis, radiography, cardiovascular catheterization, and necropsy. Necropsy findings were ventricular septal defect, atrial septal defect, patent ductus arteriosus, and congenital absence of the aortic arch....
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 ...
Slocombe JO, Rendano VT, Owen RR, Pennock PW, McCraw BM.Radiographs of the aorta and abdominal arteries were obtained from a normal anesthetized pony following catheterization of a femoral artery for nonselective, semiselective or selective arteriography. The arteries had smooth borders and regular diameters and the branches of the cranial mesenteric artery could be followed distally on the angiogram through to the smaller branches proximal to the bowel wall. Following arteriography, the pony walked normally and there were minimal alterations of the levels of serum muscle enzymes and blood lactate. The procedures for arteriography were repeated in ...
Moore JN, Kintner LD.Squamous cell carcinoma involving the pars esophagea of the stomach caused recurrent esophageal obstruction in an 11 year old Pinto gelding. The tumor encircled the esophagus and was attached to the diaphragm, spleen, aorta, left adrenal gland and kidney. Definitive diagnosis was provided by biopsy of the mass via standing left flank laparotomy.
Scott EA, Kneller SK, Witherspoon DM.The physiologic closure of the ductus areteriosus was determined in 4 foals less than 16 hours old. The common carotid artery was catheterized, using local anesthesia and tranquilization, and contrast medium was injected into the ascending aorta. Radiographs were made of heart and great vessels during and after the injection to visualize the pathway of injected contrast medium.
Harrington DD.1. The effects of feeding with a purified magnesium-deficient diet (--Mg, 7-8 mg Mg/kg) on horse foal blood serum and tissue concentrations of Mg, calcium and phosphorus were studied, and the results compared with histopathological findings. 2. Serum concentrations of Ca and P were unaffected by feeding with the --Mg diet, whereas serum Mg concentrations decreased from a mean initial (day o) concentration of 0.78 mmol/l to 0.53 mmol/l 7 d after foals were placed on the -Mg diet, and then continued to decrease at a slower rate. 3. Aorta concentrations of Ca and P, but not Mg, were positively co...
Schwarzwald C.Heart murmurs and arrhythmias are common in horses. Assessment of their clinical relevance concerning health, performance, safety and longevity of sports horses is of highest importance. A comprehensive cardiovascular examination is crucial for diagnosis and assessment of the severity of disease. Recently, an expert panel of the American College of Veterinary Internal Medicine (ACVIM) and the European College of Equine Internal Medicine (ECEIM) developed a consensus statement containing recommendations for sports horses with heart disease. This article summarizes the most relevant recommendati...
Fröhlich W, Wlaschitz S, Riedelberger K, Reifinger M.A case of endocarditis of the aortic valve in a 11 year old thoroughbred is presented. Diagnostic approach, the value of echocardiography, and the various symptoms, complications and prognosis are discussed. The horse with ruptured aortic valves due to endocarditis with severe aortic and mitral regurgitation causing congestive heart failure, was euthanised due to bad prognosis.
Smith TR.A 2.5-month-old filly was presented with signs of esophageal obstruction. The filly was euthanized and postmortem examination revealed a vascular ring anomaly. The vascular ring anomaly was not caused by a persistent right aortic arch, which is the only vascular ring anomaly reported to occur in horses. Une pouliche de 2 1/2 mois a été présentée avec des signes d’obstruction œsophagienne. Après euthanasie, l’examen a révélé une malformation vasculaire annulaire. L’anomalie vasculaire annulaire n’était pas due à la persistance de l’arc aortique droit, seule malformation va...
Valdes-Martinez A, Eades SC, Strickland KN, Roberts ED.We describe the echocardiographic findings in a 4-day-old thoroughbred foal with an aortico-pulmonary septal defect. The foal had labored breathing, cyanotic mucous membranes and a continuous grade 5/6 heart murmur with point of maximal intensity over the base of the heart on the right side. Echocardiographically, there was a large communication between the aorta and the pulmonary artery just dorsal to the base of the heart. The cardiac anomaly seen during the echocardiographic exam was confirmed at necropsy where a large communication between the two great vessels was observed. These findings...
Clark ES, Reef VB, Sweeney CR, Lichtensteiger C.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.
Knezevic PF, Fessl L.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.
Katano Y, Imai S.The effects of dipyridamole on thromboxane A2 formation by horse platelet microsomes were studied in comparison with those of imidazole, a prototype inhibitor of TXA2 synthetase and nifedipine, a calcium antagonistic vasodilator. Thromboxane A2 was synthesized by incubating PGH2 with horse platelet microsomes and was assayed on the superfused rabbit aorta. Dipyridamole induced as strong an inhibition of TXA2 synthesis as imidazole, while nifedipine was without effects. The possible beneficial clinical outcomes of this effect of dipyridamole are discussed.
Trachsel D, Cohausz O, Scharf G, Wehrli Eser M.A 14-year old Swiss warmblood gelding was presented to the equine hospital of the University of Zurich because of therapy-resistant fever. An intermittent lameness suggested the presence of an intravascular aorto-iliac thrombus which was confirmed sonographically. Subsequently, treatment was initiated with Heparin s.c. and continued for 7 months with Phenprocoumon (Marcoumar). The dosage was monitored and adjusted according to the prothrombin time, which was initially measured every week, and later maximally biweekly. The lameness improved and the regression of the thrombus could be followed s...
Brama PA, Rijkenhuizen AB, van Swieten HA, Warmerdam EP.The prognosis of aortic-iliac thrombosis (TAI) is usually considered to be poor, although affected horses are reported to have recovered following treatment with sodium gluconate. This paper presents some diagnostic techniques to monitor the development of hypoxemia in the diseased limb and to visualise the extension of the thrombosis into the femoral artery. Also, a surgical technique using a Fogarty thrombectomy catheter for partial or total removal of thrombi to restore blood flow, is described. One horse recovered completely, allowing it to resume its former career, the other horse improve...
Wallace KD, Selcer BA, Becht JL.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 ...
Reef VB, Roby KA, Richardson DW, Vaala WE, Johnston JK.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.
Amend JF, Ross JN, Garner HE, Rosborough JP, Hoff HE.This report describes the measurement of systolic time intervals in a nine year old female domestic pony which was found at necropsy to show coarctation of the aorta and bilateral ventricular hypertrophy. Electrocardiogram, phonocardiogram and direct arterial blood pressure were recorded from the pony in a standing unmedicated state and systolic time intervals were measured from the resulting tracings. A prolongation of left ventricular ejection time and shortening of the pre-ejection period were observed in comparison to a group of normal ponies similarly examined. Such changes are consistent...
Schmidt AR.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...
Hoch DH, Salazar AM, Cabin HS, Young LH.Angiography in a 30-year-old man revealed the unique combination of aortic coarctation and an unusual arch anomaly. Proximal to the coarctation, a single arch vessel trifurcated into the brachiocephalic, left common carotid and left subclavian arteries. This anomalous arch vessel is a normal equine variant.
Magalhaes HB, Canisso IF.Practitioners are frequently requested to diagnose and stage pregnancy in donkeys with unknown breeding dates; however, scant work has been done to stage pregnancy in the species. Therefore, this study aimed to determine the association between measurements of fetal aortic, thoracic, and heartbeat with gestational age in donkeys carrying and delivering healthy foals. Multiparous Dezhou donkeys (n = 50) ranging from 4 to 16 years were enrolled in the study by 150 days of gestation. Transabdominal ultrasonography coupled with a 3.5 MHz sectorial convex transducer was performed at 30 day-interv...
Moore JN, Kintner LD.Squamous cell carcinoma involving the pars esophagea of the stomach caused recurrent esophageal obstruction in an 11 year old Pinto gelding. The tumor encircled the esophagus and was attached to the diaphragm, spleen, aorta, left adrenal gland and kidney. Definitive diagnosis was provided by biopsy of the mass via standing left flank laparotomy.
Miller PJ, Holmes JR.Transaortic blood pressures were recorded in seven horses using catheter mounted transducers during various types of supraventricular arrhythmia. Changes in left ventricular (LV) and aortic (Ao) pulse contours were associated with variation in pulse interval (PI). When PI lengthened there was a rise in LV end diastolic pressure (LVEDP) associated with a prolonged filling time. In contrast, a long PI resulted in a reduced end diastolic Ao pressure (AoEDP) due to a prolonged arterial 'run off'. LVdP/dt max representing the peak rate of rise of pressure during the isovolumic contraction period wa...
Ghaly P, Di Mascio D, Vicaretti M.A common source of infection in equine, , is an uncommon pathogen in humans, rarely identified as the cause for mycotic aortic aneurysms. Typically associated with consumption of unpasteurized milk or contact with horses, can result in severe bacteremia, endocarditis and meningitis. We describe the presentation and successful management of a 69-year-old retired equestrian who underwent infrarenal aortic resection and reconstruction using autologous right femoral vein for a mycotic aneurysm.
Shojaei B, Kheirandish R, Azizi S.The present study describes the anatomical and microscopic features of a horseshoe kidney that was found in a 7-year-old male horse. The specimen consisted of two kidneys joined at their caudal poles by an isthmus composed of renal parenchyma and situated caudal to the caudal mesenteric artery. Six main renal arteries arose from the aorta and the external iliac arteries and ramified into 21 branches before entering the kidney. A hypoplastic and ectopic left testis, located in the inguinal canal, was observed as an associated anomaly.
Harrington DD.1. The effects of feeding with a purified magnesium-deficient diet (--Mg, 7-8 mg Mg/kg) on horse foal blood serum and tissue concentrations of Mg, calcium and phosphorus were studied, and the results compared with histopathological findings. 2. Serum concentrations of Ca and P were unaffected by feeding with the --Mg diet, whereas serum Mg concentrations decreased from a mean initial (day o) concentration of 0.78 mmol/l to 0.53 mmol/l 7 d after foals were placed on the -Mg diet, and then continued to decrease at a slower rate. 3. Aorta concentrations of Ca and P, but not Mg, were positively co...
Saey V, Vandecasteele T, van Loon G, Cornillie P, Ploeg M, Delesalle C, Gröne A, Gielen I, Ducatelle R, Chiers K.Acquired aortopulmonary fistulation is a rare condition in humans. It usually results as a late complication of a true or pseudoaneurysm of the thoracic aorta. It is most commonly associated with trauma or surgery, less commonly with atherosclerosis, inflammation, hypertension or Marfan's syndrome. Aortopulmonary fistulation is also seen as a rare complication of acute aortic dissection. On rare occasions, acquired aortopulmonary fistulation is reported in aged patients without any of the above mentioned triggering factors. Thus, these cases should be considered as idiopathic aortopulmonary fi...
Musselman EE, LoGuidice RJ.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...
Sikkes BP, Manohar M, Duren SE, Day J, Baker JP.Experiments were carried out on 8 healthy ponies to examine the effects of prolonged submaximal exercise on regional distribution of brain blood flow. Brain blood flow was ascertained by use of 15-microns-diameter radionuclide-labeled microspheres injected into the left ventricle. The reference blood was withdrawn from the thoracic aorta at a constant rate of 21.0 ml/min. Hemodynamic data were obtained with the ponies at rest (control), and at 5, 15, and 26 minutes of exercise performed at a speed setting of 13 mph on a treadmill with a fixed incline of 7%. Exercise lasted for 30 minutes and w...
Miller PJ, Holmes JR.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....
Carlsten J, Kvart C, Jeffcott LB.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...
