Aorto-cardiac fistulas in seven horses.

This report describes the history, clinical, electrocardiographic and echocardiographic findings, treatment, outcome and post-mortem findings in seven horses with aorto-cardiac fistula. Affected horses included 5 stallions, one gelding and one mare; 2 each of the Thoroughbred, Arabian and Standardbred breeds and one Thoroughbred-cross with a mean +/- s.d. age of 12 +/- 4 years, range 6-18 years. The presenting signs were acute distress (four horses), exercise intolerance (two horses) and the lesion was detected during a routine examination in one horse. Five horses had monomorphic ventricular tachycardia on admission and one other had a history of this arrhythmia. Five horses had a characteristic continuous murmur loudest in the right fourth intercostal space. Echocardiography (six horses) and/or post-mortem examination (four horses) revealed the horses had aorto-cardiac fistulas arising from the right aortic sinus in all five horses in which the site was recorded. Two horses had ruptured aneurysmal dilatations of the aortic wall at this site. Fistulas extended into the right ventricle in four horses; the right atrium in two horses, the left ventricle in one horse, and five horses had dissecting tracts in the septal myocardium. Horses survived for periods ranging from 24 h to 4 years. Aorto-cardiac fistula should be considered in the differential diagnosis for horses presenting with acute distress, bounding arterial pulse, a right-sided continuous murmur and/or monomorphic ventricular tachycardia, particularly in middle-aged or older stallions. Echocardiography is the technique of choice for confirming the diagnosis and demonstrating accompanying cardiac changes.

Bacterial endocarditis in horses: ten cases (1984-1995).

A retrospective study of 10 horses with bacterial endocarditis was performed in order to describe the echocardiographic findings in horses with bacterial endocarditis, in conjunction with clinical signs and post mortem findings, and to evaluate the usefulness and the formulation of a prognosis. Echocardiographic and post mortem examinations were performed in 7 horses. Post mortem examination alone was performed in 2 horses and echocardiographic examination alone performed in one horse. No breed or sex predilection was obvious. Mean age +/- s.d. was 2.12 +/- 3.32 years. Predominant clinical signs and abnormal clinical pathology data were fever, cardiac murmur, tachycardia, tachypnoea, hyperfibrinogenaemia, anaemia and leucocytosis. Pasteurella/Actinobacillus spp. and Streptococcus spp. were most commonly cultured. Vegetative lesions were found most frequently on the mitral valve and secondarily on the aortic valve. The location and number of lesions identified with echocardiography in the horses accurately described the lesions found on post mortem examination. Medical treatment was attempted in 50% of the horses. Serial echocardiography was used to assess the response to treatment in 2 horses. All horses with vegetative lesions of the mitral and/or aortic valve died or were subjected to euthanasia due to the severity of their cardiac disease. Both horses with tricuspid valve endocarditis were cured of the infection, one horse returned to racing after antimicrobial therapy and the other was subjected to euthanasia due to severe laminitis.

First-pass radionuclide angiography in the diagnosis of aortoiliac thromboembolism in a horse.

First-pass radionuclide angiography of the terminal aorta was performed in 3 normal horses and a 6-year-old Standardbred intact male with aortoiliac thromboembolism. Thromboembolism caused chronic bilateral hind limb lameness, more severe in the right hind limb, was detected by rectal examination, and confirmed using transrectal ultrasonography. Using 99mTc-HDP, first-pass radionuclide angiography was combined with hind limb and pelvis bone (delayed) scintigraphy and revealed marked reduction in blood flow through both external iliac arteries and absence of blood flow in the internal iliac arteries. Quantitative analysis showed a decreased activity in the right iliac vessels in the clinic patient consistent with reduced blood flow when compared to control horses. First-pass radionuclide angiography provided a method to obtain diagnostic images of the terminal aorta and branches and a method to diagnose aortoiliac thromboembolism in the horse.

The use of ultrasound to study the prevalence of hydatid cysts in the right lung and liver of sheep and goats in Turkana, Kenya.

Ultrasound examination of the liver and right lung was performed in 260 sheep and 320 goats from the Turkana district of Kenya. Hydatid cysts were visualized in 9.2% of the sheep and 2.5% of the goats. Of the animals positive on ultrasound, 87.5% received post-mortem examinations. Eighteen (6.9%) sheep and 5 (1.5%) goats were positive for hydatid cysts on ultrasound and post-mortem examination. False-positives were a result of Taenia hydatigena cysticerci present in the liver in all but 1 case. Positive predictive value of ultrasound for diagnosis of hydatidosis in sheep and goats was 82.1%.

Effects of furosemide, exercise, and atropine on tracheal mucus transport rate in horses.

Effects of furosemide, exercise, and atropine on tracheal mucus transport rate (TMTR) in horses were investigated. Atropine (0.02 mg/kg of body weight) administered IV or by aerosolization significantly (P < 0.05) decreased TMTR at 60, but not at 30 minutes after its administration in standing horses. Furosemide (1.10 mg/kg, IV) did not have any significant effect on TMTR when measured at 2 or 4 hours after its administration in standing horses. Exercise alone or furosemide (1.10 mg/kg, IV) administration followed 4 hours later by exercise did not alter TMTR, compared with values for standing control or exercised horses administered saline solution. Atropine (0.02 mg/kg, IV) administered after exercise significantly (P < 0.05) decreased TMTR, compared with values for no exercise standing controls, for exercise after administration of saline solution, and for furosemide and exercise.

Hydrops amnii in a mare.

A multiparous pregnant Welsh Pony mare was examined because of anorexia, dyspnea, and a large abdomen. Ultrasonography of the uterus revealed an excessive amount of amniotic fluid surrounding the fetus. Transabdominal ultrasonography permitted differentiation of hydrops amnii from hydrops allantois. The mare aborted a 7-month-old fetus with brachygnathia and a large, edematous umbilical cord. Hydrops amnii, an excessive accumulation of amniotic fluid in the amniotic cavity, is most commonly reported in cattle and sheep.

Use of a bovine hemoglobin preparation in the treatment of cyclic ovarian hemorrhage in a miniature horse.

Anemia that was secondary to ovarian hemorrhage in a 4-year-old miniature horse mare was treated prior to laparotomy with polymerized ultrapurified bovine hemoglobin (PUBH). Two previous whole-blood transfusions had resulted in acute transfusion reaction, and a suitable blood donor could not be found among 9 horses, necessitating use of the blood substitute. Subsequent blood typing revealed the mare to be Aa-negative, with allo-antibodies against Aa in serum. Serious adverse reactions were not observed after infusion of PUBH, and the mare recovered. Although the safety and efficacy of using PUBH in horses has not been established, PUBH may prove to be an excellent alternative to whole-blood transfusions, when indicated.

Unusual internal carotid artery branching that prevented arterial occlusion with a balloon-tipped catheter in a horse.

A mare with hemorrhage caused by guttural pouch mycosis was treated by insertion of a balloon-tipped catheter into the left internal carotid artery. During recovery from general anesthesia, the mare had profuse epistaxis, and was anesthetized again to determine the site of hemorrhage. The affected guttural pouch was opened to confirm that hemorrhage was from the left internal carotid artery. The mare was euthanatized, and, at necropsy, the balloon catheter was found in an aberrant branch that arose from the internal carotid artery and joined the basilar artery. The mycotic plaque was on the left internal carotid artery, distal to the origin of the aberrant branch, so that the balloon did not obstruct retrograde flow through the infected segment. Additional dissection of the internal carotid artery before insertion of a balloon catheter is recommended to identify any aberrant branches. Ligation of aberrant branches at their bifurcation with the internal carotid artery is recommended to prevent both inadvertent catheterization and retrograde flow from the cerebral arterial circle.

Hemorrhage into the guttural pouch (auditory tube diverticulum) associated with rupture of the longus capitis muscle in three horses.

Three horses were determined to have hemorrhage into a guttural pouch unassociated with mycosis, empyema, neoplasia, or foreign body. The source of the hemorrhage appeared to be the rupture of the longus capitis muscle and its associated vascular supply.

Endoscopic findings in the upper respiratory tract of 678 Thoroughbred racehorses.

The frequency of upper respiratory tract abnormalities was determined in a selected population of racing Thoroughbreds. The prevalence of pharyngeal lymphoid hyperplasia was 34.2%; left laryngeal hemiplegia was 1.8%; and epiglottic entrapment was 0.74%. Excluding pharyngeal lymphoid hyperplasia and tracheal exudate, 3.7% of the population examined had upper respiratory tract abnormalities.

Echocardiographic detection of an intact aneurysm in a horse.

Two-dimensional real-time echocardiographic examination of a 3-year-old Thoroughbred gelding with pleuropneumonia revealed an intact aneurysm of the right sinus of Valsalva, which was confirmed at postmortem examination. The horse had no clinical signs associated with the aneurysm.

Effects of furosemide on the racing times of Thoroughbreds.

The effects of furosemide on the racing times of 79 horses without exercise-induced pulmonary hemorrhage (EIPH) and 52 horses with EIPH were investigated. Racing times were adjusted to 1-mile equivalent racing times by 2 speed handicapping methods, and analysis of covariance was used to adjust actual racing times by winning time and distance for each race. All 3 methods of determining racing time indicated that geldings without EIPH had significantly faster racing times (P less than 0.05) when given furosemide before racing than when furosemide was not given before racing. Females and colts without EIPH were determined to have faster racing times when furosemide was given before racing, but the difference was not significant. Geldings with EIPH had significantly faster racing times (P = 0.0231) when given furosemide before racing, as determined by one of the speed handicapping methods. There was a strong correlation (range 0.9314 to 0.9751) between the 1-mile equivalent racing times, as determined by the 2 speed handicapping methods for horses with and without EIPH. Furosemide failed to prevent the development of EIPH in many horses that were previously considered to be EIPH-negative. When given furosemide, 62 (25.3%) of 235 EIPH-negative horses were EIPH-positive after racing. Furosemide had questionable efficacy for prevention of EIPH in known EIPH-positive horses. Thirty-two (61.5%) of 52 EIPH-positive horses given furosemide before a race remained EIPH-positive after that race.