Heart murmurs in horses are audible vibrations or sounds produced by turbulent blood flow within the heart or large blood vessels. These sounds are detected during auscultation and can vary in intensity, timing, and duration. Heart murmurs may be associated with structural heart abnormalities, such as valvular insufficiencies or septal defects, or they might occur in the absence of any underlying pathology, often termed "innocent" murmurs. The evaluation of heart murmurs involves assessing their characteristics and potential impact on the horse's cardiovascular function. This page compiles peer-reviewed research studies and scholarly articles that explore the etiology, classification, and clinical implications of heart murmurs in equine patients.
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.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.
Reynolds DJ, Nicholl TK.A 5 month old colt foal with recurrent pyrexia and a loud pansystolic murmur later developed signs of cardiac failure. Peritoneal fluid and blood samples both demonstrated an extreme leucocytosis and neutrophilia. At post-mortem both a cranial mesenteric arteritis and the congenital cardiac anomaly, Tetralogy of Fallot were found. The detailed clinical and post-mortem findings contributing to the case are described.
Button C, Gross DR, Allert JA, Kitzman JV.An Arabian crossbred foal was examined because of a suspected congenital cardiac anomaly. There was a grade V/V crescendo-decresendo holosystolic murmur and thrill in the left 4th intercostal space. The foal was slightly cyanotic and polycythemic. Electrocardiography suggested left ventricular hypertrophy. Angiography and cardiac and vascular pressure recordings led to a diagnosis of pulmonic stenosis. The foal died after cardiac bypass and corrective surgery. Postmortem examination revealed an enlarged right atrium, atresia of the tricuspid orifice, a large, fenestrated patent foramen ovale, ...
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....
Critchley KL.A 6 month Welsh pony filly with an interventricular septal defect in conjunction with a pulmonary stenosis due to a bicuspid pulmonary valve is described. The animal had poor exercise tolerance, a loud pansystolic murmur and a precordial thrill. Blood pressure and oxygen tension values obtained during cardiac catheterization suggested the diagnosis which was confirmed at autopsy.
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...
Glazier DB, Farrelly BT, O'Connor J.A congenital heart defect characterised by persistent patency (open-ness) of the ventricular septum, permitting flow of blood directly between ventricles, bypassing the pulmonary circulation and resulting in various degrees of cyanosis (blue discolouration of the skin) due to oxygen deficiency. Clinical signs include systolic murmur and a palpable thrill on both sides of the chest, dyspnoea and poor tolerance of exercise.
Vitums A, Grant BD, Stone EC, Spencer GR.ABSTRACT Transposition of the aorta to the right ventricle with atresia of the pulmonary trunk was described in a 2 year old horse. Clinical and physiological examinations were performed and data recorded. Teratogenesis of the present anomaly was discussed and the literature reviewed. The probable course of circulation during the fetal life and after birth of this animal was suggested. An extensive col-lateral circulation was developed to the lungs, which might explain how the animal could live so long.
Holmes JR, Alps BJ.The paper describes observations on the distributions of the P, QRS and T cardiac vectors in the horizontal plane, comparing healthy horses with those with arrhythmia and cardiac murmurs. Deviation of the T vector from the normal range appeared to occur most commonly in association with cardiac murmurs, particularly those involving the semilunar valves and aorta.
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...
Sleeper MM, Durando MM, Miller M, Habecker PL, Reef VB.Clinical findings in 4 horses with aortic root disease are described. Three of the horses had aneurysms of the right aortic sinus, and in 2 of the 3, the aneurysm ruptured, creating a fistula between the aorta and right ventricle. One of these horses had had a murmur since birth, and the aortic sinus aneurysm may have been a congenital anomaly. In a second horse, the aneurysm may have been an acquired condition that developed secondary to chronic aortic regurgitation. Another horse had a large subendocardial hematoma associated with dissection of blood from the aorta to the interventricular se...
Xue C, Cavanaugh SM.Reports of ante-mortem diagnosis of cardiovascular diseases in donkeys (Equus asinus) are rare. This case report describes the echocardiographic findings of suspected mitral valve dysplasia in a 3-year-old Nevisian donkey jenny presented for evaluation of a grade III/VI left-sided systolic murmur. Pertinent findings on transthoracic echocardiography included double mitral regurgitant jets and a bridge of tissue between the septal and mural mitral leaflets. Based upon the mild degree of cardiac remodeling and absence of clinical signs, therapeutic intervention was deemed unnecessary, and the je...
Khalesi H, Sakha M, Veshkini A, Rezakhani A.Heart murmurs and valvular regurgitation are common in horses and often have no effect on their performance. However, when structural changes occur in the heart size, they can affect performance adversely. This study aimed to examine the correlation between cardiac valves disease and poor performance in athletic horses. A total of 300 athletic Thoroughbred and mix-breed horses including 164 mares and 136 stallions, with a history of poor performance, were selected. Horses with cardiac murmurs were identified and further cardiac examination including precise auscultation, base-apex electrocardi...
De Lange L, Vernemmen I, van Loon G, Decloedt A.The ductus arteriosus (DA) and foramen ovale (FO), including the septum primum (SP) and septum secundum (SS), are important structures in fetal circulation and are unexplored in neonatal equids. The objective of this study is to describe echocardiographic characteristics in a hospital-based population of neonatal foals. On days 2, 5 and 10 after parturition, cardiac ultrasound was performed, and clinical data were collected in healthy and diseased Warmblood foals. Fifty healthy ( = 15) and diseased ( = 35) Warmblood foals were examined. A left-sided and right-sided holosystolic murmur was audi...
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...
Helwegen MM, Young LE, Rogers K, Wood JL.The effect of tricuspid valve regurgitation (TR) in right ventricular (RV) chamber size has not been reported. Methods: An echocardiographic and auscultation study was conducted on 394 race-fit National Hunt Thoroughbreds (TBs) in 4 training yards. Auscultation was performed on each horse and audible murmurs of TR graded using a 1-6 scale. Echocardiography was also performed and standard, 2-dimensional (2D), short (SA) and long axis (LA) images of the RV obtained from a right parasternal location. An m-mode image was recorded from an SA view of the RV just below the level of the tricuspid valv...
Brown CM.This article reviews the etiology, clinical findings, and significance of diseases of the heart valves, myocardium, pericardium, and great vessels of the horse. Each valve is considered separately from the point of view of murmur production. In addition, the role of the cardiovascular system in the etiology of sudden and unexpected death is considered.
Naylor JM, Yadernuk LM, Pharr JW, Ashburner JS.The ability of clinicians, ie, 10 veterinary students, 10 general practitioners, and 10 board certified internists, to describe and interpret common normal and abnormal heart sounds was assessed. Recordings of heart sounds from 7 horses with a variety of normal and abnormal rhythms, heart sounds, and murmurs were analyzed by digital sonography. The perception of the presence or absence of the heart sounds S1, S2, and S4 was similar for clinicians irrespective of their level of training and was in agreement with the sonographic interpretation on 89, 82, and 78% of occasions, respectively. Howev...
Young LE, Rogers K, Wood JL.Cardiac murmurs associated with valvular regurgitation occur commonly in conditioned performance horses, but their association with athletic performance is unknown. Objective: Cardiac valvular regurgitation has a negative association with race performance. Methods: Five hundred and twenty-six "race fit" Thoroughbred racehorses engaged in either flat (race distance 1,000-2,500 m) or jump racing (race distance 3,200-6,400 m). Methods: Cardiac auscultation and color flow Doppler (CFD) echocardiography were performed on 777 occasions. The associations between the presence and severity of either an...
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.
Reynolds DJ, Nicholl TK.A 5 month old colt foal with recurrent pyrexia and a loud pansystolic murmur later developed signs of cardiac failure. Peritoneal fluid and blood samples both demonstrated an extreme leucocytosis and neutrophilia. At post-mortem both a cranial mesenteric arteritis and the congenital cardiac anomaly, Tetralogy of Fallot were found. The detailed clinical and post-mortem findings contributing to the case are described.
Marr CM.Respiratory and cardiac diseases are common in older horses. Advancing age is a specific risk factor for cardiac murmurs and these are more likely in males and small horses. Airway inflammation is the most common respiratory diagnosis. Recurrent airway obstruction can lead to irreversible structural change and bronchiectasis; with chronic hypoxia, right heart dysfunction and failure can develop. Valvular heart disease most often affects the aortic and/or the mitral valve. Management of comorbidity is an essential element of the therapeutic approach to cardiac and respiratory disease in older e...
Vitums A, Grant BD, Stone EC, Spencer GR.ABSTRACT Transposition of the aorta to the right ventricle with atresia of the pulmonary trunk was described in a 2 year old horse. Clinical and physiological examinations were performed and data recorded. Teratogenesis of the present anomaly was discussed and the literature reviewed. The probable course of circulation during the fetal life and after birth of this animal was suggested. An extensive col-lateral circulation was developed to the lungs, which might explain how the animal could live so long.
Caivano D, Cicogna M, Orvieto S, Spitale D, Porciello F.A 16-year-old horse, 400 kg, male, Quarter horse gelding was examined for a cardiac murmur that had not been previously heard. Physical examination revealed a regularly irregular pulse and a grade III/VI, decrescendo, diastolic murmur with a point of maximum intensity over the left heart base. Base-apex standard electrocardiographic examination at rest showed sinus rhythm with second-degree atrio-ventricular blocks. Echocardiography identified the presence of four aortic valve cusps, two equal larger and two unequal smaller cusps. Color flow Doppler examination showed a diastolic regurgitant j...
Calewaert A, Palarea-Albaladejo J, Coultous R, Capewell P, Hanks E, Decloedt A, van Loon G.MicroRNA (miRNA) has previously been used as a biomarker for cardiac disease in humans and dogs, however, studies in horses are not yet available. Objective: To determine if adult horses with moderate or severe mitral valve regurgitation have a different serum miRNA expression profile compared to healthy controls. Methods: Retrospective cross-sectional. Methods: Serum samples from 77 adult horses with moderate or severe mitral valve regurgitation and 77 healthy control horses were analysed using a commercial cardiac disease-specific miRNA panel previously used in dogs. Results: The commercial ...
Bindi F, Bozzola C, Vezzosi T, Zucca E, Caivano D, Freccero F, Sala G, Sgorbini M.Smartphone-based technology is increasingly used in veterinary medicine as a complementary tool for cardiac auscultation and ECG recording. This prospective observational study evaluates a digital stethoscope (DS) that consists of simultaneous phonocardiographic and one-lead ECG recording (dECG) in adult horses, comparing it with auscultation using a conventional stethoscope (CS) and reference base-apex ECG (rECG). A total of 104 horses underwent cardiac auscultation using CSs and DSs to detect arrhythmias and murmurs. Audio and dECG were acquired using the DS. The rECG tracings were also reco...
Foreman JH, Tennent-Brown BS, Oyama MA, Sisson DD.Cardiac troponin-I (cTnI) is a highly sensitive and specific marker of myocardial injury detectable in plasma by immunoassay techniques. Inclusion criteria over a 3-year period required a diagnosis of cardiac disease accompanied by electrocardiographic (ECG) and cardiac ultrasound examinations (n = 23) in adult horses (≥2 years of age). A second group of normal adult ponies (n = 12) was studied as a reference group. Heparinized jugular venous blood samples were collected and centrifuged within 30 min, and the plasma was separated and frozen at -70 °C for subsequent batched cTnI analysis. Th...
Munerato MS, Simon O, Nicholson A.This report describes successful cardiopulmonary resuscitation of a healthy, 525 kg, 8 years 9 months-old Quarter horse gelding. After successful pelvic limb orthopaedic surgery to excise a metatarsal bone under general anaesthesia, with the horse in left lateral recumbency, the horse was hoisted into recovery. After the horse was positioned in recovery, a routine cardiac check by thoracic auscultation was performed. Cardiopulmonary arrest (CPA) was identified by absence of cardiac sounds and pulse, as evaluated by digital palpation of the facial artery, absence of the right palpebral reflex, ...
