Complete atrioventricular canal defect in a foal: Clinical and pathological features

Atrioventricular (AV) canal defects comprise a rare category of congenital heart disease associated with abnormal development of the endocardial cushions. These anomalies include a broad spectrum of lesions involving the atrial septum primum, the inlet portion of the ventricular septum, and the atrioventricular valves. In severe cases heart failure may result. The present report describes cardiopulmonary findings in a six-week-old, female Thoroughbred foal with persistent tachypnea and tachycardia since birth. Clinical, echocardiographic, cardiac catheterization, and pathologic findings were compatible with complete AV canal defect with bi-directional shunting, congestive heart failure, and pulmonary hypertension. Gross cardiac pathologic findings included a large atrioventricular septal defect, a common atriovalvular orifice, five atrioventricular leaflets, with two free-floating bridging leaflets. Histopathologic lesions in the lung included hypertrophy of the pulmonary arteriolar walls due to thickening of the tunica media. This represents a well documented case of complete endocardial cushion defect with anomalous development of the atrioventricular valves and resultant pulmonary hypertension and heart failure.     

Cardiovascular images: vascular hamartoma of the mitral valve in a horse

An 8-month-old Hanoverian gelding was presented with a history of cardiac murmurs that were not apparent as a foal nor reported at the time of castration. Major echocardiographic findings included mitral valvular thickening, functional stenosis, and mitral regurgitation of sufficient severity to cause diastolic and systolic cardiac murmurs, left-sided volume overload, and pulmonary hypertension. Due to the hemodynamic severity of the lesion and poor prognosis for future performance and longevity, euthanasia was elected. On gross postmortem examination, there was focal fibrous epicarditis affecting the heart base, and the left atrium was moderately dilated. The mitral valve surface was irregular and contained several nodules along the atrial face of the cusp. Histologically, this lesion was diagnosed as a vascular hamartoma, which is rarely reported in veterinary species and has not been described in heart valves. This benign proliferative lesion, and concurrent valvular dysfunction, was associated with an unusual manifestation of clinically evident disease and should be differentiated from common incidental valvular lesions such as hematocysts.     

ECHOCARDIOGRAPHIC DIAGNOSIS OF TRANSPOSITION OF THE GREAT ARTERIES IN A NEONATAL FOAL

The clinical and echocardiographic findings in a 19-h-old female foal with a ventricular septal defect, patent foramen ovale, patent ductus arteriosus, and complete transpositon of the great vessels are described. Clinical signs were suggestive of complex congenital heart disease and echocardiography of the foal allowed definitive diagnosis prior to postmortem.     

Echocardiographic detection of tricuspid atresia in two foals

M-mode, 2-dimensional, and contrast echocardiographic studies were used to detect tricuspid atresia in 2 foals. M-mode echocardiographic findings included a small right ventricle, large left ventricle, large mitral valve excursion, large left atrium (foal 2), dropout of the cranial aspect of the aortic root, and a thick band of echoes in the tricuspid valve region. These findings were confirmed by 2-dimensional echocardiography. In addition, a large right atrium, persistent foramen ovale, ventricular septal defect, and large mitral valve apparatus were imaged. One foal also had a thick right atrial wall. Contrast echocardiography confirmed the intracardiac flow of blood from right to left atrium and then to the left ventricle, followed by simultaneous opacification of the right ventricle and aorta. The use of these echocardiographic techniques enables accurate antemortem diagnosis and prognosis of tricuspid atresia in the foal.     

Tricuspid atresia in a foal

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, eccentric left ventricular hypertrophy, and a large interventricular septal defect. The right ventricle had a small lumen and a relatively thick wall. There was valvular and supravalvular pulmonic stenosis, with poststenotic dilatation of the pulmonary artery. A single coronary artery originated from the anterior sinus of the aorta.     

Congenital malformations of the tricuspid valve in domestic carnivores: a retrospective study of 50 cases

A retrospective study was done on 14 cats and 36 dogs diagnosed with right atrioventricular valve malformations (RAVM), either tricuspid dysplasia (n = 38) or Ebstein's anomaly (n = 12). Comparison with a large reference population including 85 250 animals allowed an epidemiologic analysis of these RAVM, demonstrating that Labrador, Boxer and Chartreux cats had a 35, 7 and 11-fold higher risk respectively to be affected by one of these heart diseases than other breeds, without sexual predisposition. In 93% of cases, cardiac auscultation revealed a heart murmur, whose grade was not significantly correlated with the echographic stages of the valvular disease. The echocardiographic examination confirmed the frequent association between RAVM and other congenital anomalies, particularly mitral dysplasia, in 84% and 20% of tricuspid dysplasia and Ebstein anomaly respectively. Last, the prognosis of RAVM was worsened by atrial fibrillation and right-sided heart failure.     

Uhl's anomaly in a domestic shorthair cat

A 2-year-old, neutered male, domestic shorthair cat was presented for investigation of dyspnea and episodic weakness. Clinical and ultrasonographic features were consistent with right ventricular cardiomyopathy. Pathological findings documented Uhl's anomaly. Although rare, Uhl's anomaly should be a differential diagnosis for cats with right-sided congestive heart failure. In particular, Uhl's anomaly could be misdiagnosed as arrhythmogenic right ventricular cardiomyopathy due to the similarity of clinical and echocardiographic findings.     

Right atrioventricular atresia and ventricular septal defect in a foal

Right atrioventricular atresia with a ventricular septal defect, a rare congenital cardiac anomaly of either animals or man, was diagnosed in a one week old Arabian foal. The foal had been weak and cyanotic since birth, sometimes becoming dyspneic when stressed. Necropsy revealed a dilated and hypertrophied left ventricle with the right ventricle being small. The right atrioventricular valve was absent. The right and left ventricles communicated via a septal defect which was located immediately adjacent to the aortic valve.     

Ventricular septal defects in the horse

Clinical, echocardiographic, and right-side cardiac catheterization data were collected in 6 horses with ventricular septal defects. The defects were confirmed by necropsy in 5 horses. On echocardiography, the cardiac dimensions were normal in 3 horses and enlarged in 2 others. A step-up in partial oxygen pressure between right atrium and right ventricle suggested a left-to-right shunt in 3 of the 4 horses catheterized. In 1 foal, a small defect without PO2 step-up was documented by angiocardiography. The oxymetry and pressure data were compared with previous cases from the reviewed literature, and the importance of pressure measurements to rule out concomitant defects was emphasized.     

Double-outlet right ventricle in an Angus calf

Double-outlet right ventricle (DORV) is a conotruncal malformation where both great arteries arise from the right ventricle. Anatomic variations of DORV are classified according to the position of the great arteries in relation to each other, the relationship between a ventricular septal defect (VSD) and the great arteries, and the presence and degree of pulmonary stenosis. The prevalence of congenital cardiac defects in bovine fetuses has been reported at approximately 0.7 %, with VSDs representing the most common congenital cardiac defect. DORV has been described in veterinary literature in few cats and dogs, a foal, and 2 calves with variable clinical and pathologic documentation. In this report, we describe the angiographic, echocardiographic, and postmortem examination findings in a calf with a DORV with concurrent pulmonary stenosis, subaortic VSD, patent ductus arteriosus (PDA), aberrant left subclavian artery, and a tracheal malformation.     

Left coronary aneurysmal dilation and subaortic stenosis in a dog

A 6-month-old German shepherd dog was referred for evaluation of a cardiac murmur.Upon physical examination, the auscultated heart rate was 120 beats/min, and a grade IV/VI systolic heart murmur with a point of maximal intensity over the left heart base radiating up the neck was heard. The standard echocardiographic examination showed subaortic stenosis and an anechoic tubular structure extending from the sinus of Valsalva to the left ventricular posterior wall. Aneurysmal left coronary artery (CA) was confirmed by angiography. The dog was euthanized and post-mortem examination showed severe dilatation of the proximal left CA and confirmed the subaortic stenosis. Histopathology did not demonstrate abnormalities in the walls of the CA, aorta or pulmonary artery.The exact cause of the CA aneurysmal dilation remains unknown. Subaortic stenosis, elevated coronary vascular resistance or a congenital anomaly may have contributed to the dilation.To our knowledge, coronary aneurysmal dilation has never been described in dogs. Standard echocardiography provides reliable information on coronary anatomy.     

Reversed patent ductus arteriosus and multiple congenital malformations in an 8‐day‐old Arabo‐Friesian foal

An 8‐day‐old Arabo‐Friesian filly was presented with signs of severe dyspnoea, tachypnoea, coughing and cyanotic mucous membranes. On auscultation, a bilateral grade V/VI continuous heart murmur and heart rate of 155 beats/min (sinus tachycardia) were detected. Lung ultrasonography revealed pronounced comet tail artefacts indicating lung oedema. Echocardiography showed right ventricular hypertrophy, a 1.2 cm muscular ventricular septal defect with a left‐to‐right shunt, a stenotic bicuspid pulmonary valve and severe mitral and tricuspid valve regurgitation. Tricuspid regurgitation peak velocity indicated a right ventricular systolic pressure of 119 mmHg. The pulmonary artery was severely dilated and a 1 cm diameter patent ductus arteriosus was found. Colour flow Doppler showed systolic ductal flow reversal with right‐to‐left shunting through the ductus. Arterial partial oxygen pressure and saturation were lower in the metatarsal artery (25 mmHg, saturation 52.6%) than in the carotid artery (31 mmHg, saturation 64.3%). Due to the poor prognosis, the foal was subjected to euthanasia and necropsy confirmed the ultrasonographic findings. Patent ductus arteriosus is a rare condition and occurs most frequently in combination with tetralogy and pentalogy of Fallot. A genetic basis for congenital cardiac disease, especially for ventricular septal defects, in Arabians and for aortic rupture and aorto‐pulmonary fistulation in Friesians has been reported. Whether cross‐breeding leads to an increased prevalence is unknown. This is the first case report with echocardiographic visualisation of reversed ductal flow in a neonatal Arabo‐Friesian foal.     

Congenital Cardiac Defects in Neonatal Foals: 18 Cases (1992–2007)

Background: Literature available regarding congenital cardiac defects in foals is limited to reports of individual cases or small case series.
Objective: To describe the clinical, echocardiographic, and necropsy findings and breed predilection of congenital cardiac defects in neonatal foals.
Animals: Eighteen foals <15 days of age with 1 or more congenital cardiac defects.
Methods: Medical records of foals diagnosed with congenital cardiac defects at the William R. Pritchard Veterinary Medical Teaching Hospital were reviewed. Data collected included history, signalment, clinical signs, laboratory data, diagnostic and necropsy results, and outcome.
Results: Arabian foals represented 39% of cases with congenital cardiac defects and were significantly ( P = .004) overrepresented (OR = 4.7 [CI: 1.8–12.4]) compared with the general hospital population. Ventricular septal defect (VSD) (14/18), tetralogy of Fallot (5/18), and tricuspid valve atresia (4/18) were the most common defects identified. A ≥3/6 heart murmur (14/14) accompanied by tachycardia (14/17), tachypnea (17/17), and cyanosis of mucous membranes (7/16) were the most common clinical signs. Concurrent congenital defects were common (9/18). Two foals, both with VSD, survived for ≥ 8 years after diagnosis and 1 was a successful performance horse.
Conclusions and Clinical Relevance: Arabian horses appear to have a predisposition for cardiac defects. The presence of a loud murmur (≥ 3/6), cyanotic membranes, and tachycardia or tachypnea in a neonatal foal should warrant thorough evaluation of the heart for congenital defects. Foals with cardiac defects should be closely evaluated for concurrent congenital defects in other body systems.     

Gastrointestinal nonrotation in a neonatal foal

A 24‐hour‐old Welsh‐Thoroughbred foal presented for routine surgical repair of an abdominal and body wall hernia. The colt became acutely colicky and emergency celiotomy was performed revealing abnormal anatomical configuration of the gastrointestinal tract (GIT). Incomplete gastrointestinal rotation is a rare congenital anomaly only described in man. This report describes the clinical and diagnostic findings, surgical and medical treatment, and outcome of a neonatal foal with nonrotation of the GIT.     

Surgical Correction of a Persistent Right Aortic Arch in a Foal

A persistent right fourth aortic arch causing esophageal stenosis was diagnosed in a foal. Presenting signs included cervical swelling that developed following introduction to solid feed at weaning, and symptoms of chronic aspiration pneumonia. The esophagus was distended at the thoracic inlet; neither an endoscope nor a small nasogastric tube could be passed through the strictured esophagus at the heart base. The esophagus was seen to be dilated to the level of the heart base on plain and contrast radiographs. A left lateral thoracotomy through the fifth intercostal space was used to gain access for surgical correction of the defect. Radiographic and clinical evaluation of the foal 2 and 6 months following surgery showed a gradual decrease in size of the esophageal dilatation and an enlargement in the functional diameter of the esophagus at the previously strictured area at the heart base. Ten months following surgery the colt was eating normally and was of normal height and weight.     

Exsanguination due to gastric ulceration in a foal

An Arabian foal with a congenital heart disease died due to hemorrhage secondary to a large gastric ulcer. Previously, death of foals with gastric ulcers has been due to diffuse peritonitis resulting from gastric ulcer perforation. The foal in this case report died due to hemorrhage secondary to a large gastric ulcer.     

Atrial septal defect in five dogs

The clinical, electrocardiographic, radiographic, and two-dimensional, M-mode and Doppler echocardiographic findings of five cases of canine ostium secundum type atrial septal defect (ASD) are described. The atrial septal anomaly was associated with other congenital cardiac abnormalities in two dogs: ventricular septal defect in one case and tricuspid dysplasia in the other. ASD was found in addition to dilated cardiomyopathy and suspected atrial thrombosis in one geriatric dog, but was the only cardiac abnormality detected in the remaining two dogs. Colour Doppler imaging facilitated the diagnosis of ASD in all subjects. The long-term prognosis for dogs with isolated and small-sized ASD is usually good, but can be compromised by the presence of concurrent congenital or acquired cardiac diseases.     

Congestive heart failure in horses: 14 cases (1984-2001)

OBJECTIVE: To identify clinical signs, underlying cardiac conditions, echocardiographic findings, and prognosis for horses with congestive heart failure. DESIGN: Retrospective study. ANIMALS: 14 horses. PROCEDURE: Signalment; history; clinical signs; clinicopathologic, echocardiographic, and radiographic findings; treatment; and outcome were determined by reviewing medical records. RESULTS: All 14 horses were examined because of a heart murmur; tachycardia was identified in all 14. Twelve horses had echocardiographic evidence of enlargement of 1 or more chambers of the heart. Other common clinical findings included jugular distention or pulsation, crackles, cough, tachypnea, and ventral edema. Nine horses had signs consistent with heart failure for > 6 days. Underlying causes for heart failure included congenital defects, traumatic vascular rupture, pericarditis, pulmonary hypertension secondary to heaves, and valvular dysplasia. Seven horses were euthanatized after diagnosis of heart failure; 5 were discharged but were euthanatized or died of complications of heart disease within 1 year after discharge. The remaining 2 horses were discharged but lost to follow-up. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that congestive heart failure is rare in horses. A loud heart murmur accompanied by either jugular distention or pulsation, tachycardia, respiratory abnormalities (crackles, cough, tachypnea), and ventral edema were the most common clinical signs. Echocardiography was useful in determining the underlying cause in affected horses. The long-term prognosis for horses with congestive heart failure was grave.     

Imaging diagnosis and clinical presentation of a Chiari malformation in a Thoroughbred foal

A newborn Thoroughbred foal was presented to the clinic with ambiguous neurological deficits, spinal anomalies and a soft tissue swelling dorsal to the lumbar vertebral column. The foal was alert but unable to rise and stand. With radiography, ultrasonography, computed tomography (CT) and magnetic resonance imaging (MRI) a lumbar dysraphic anomaly, cerebellar herniation and coincidental skeletal abnormalities were documented. Finally, a meningomyelocele was defined and, in context with the cerebellar herniation through the foramen magnum, the foal was diagnosed to have a Chiari malformation. The MRI examination corresponded best with the post mortem findings. Although 3‐dimensional imaging methods have been considered superior regarding full and detailed assessment of the congenital malformation, radiography and ultrasonography also provide essential information to diagnose dysraphic lesions at reduced costs and efforts. A Chiari malformation should be considered as a differential diagnosis in foals with neurological deficits.