Factors associated with gastric lesions in thoroughbred racehorses.

Gastroscopic examinations were performed on 67 Thoroughbred horses in training at a race track and repeat examinations performed in 35 horses, 2 to 3 months later. Horses were age 2-9 years and included 16 two-year-olds, 32 three-year-olds and 19 horses > or = 4-years-old. Forty-two of the 67 horses had raced within the 2 months before the initial examination and the remaining 25 horses were in training. Sixty-two of the 67 horses (93%) had one or more lesions present in the gastric mucosa and lesions were present in all of the 42 horses that had raced. Thirty-two of the 35 horses, examined twice (91%), had gastric lesions on the first examination and all had lesions on the second examination. Four sites of the gastric squamous epithelium were graded for lesion severity on a scale of 0 to 10 and the mean maximum squamous mucosal lesion score was significantly (P < 0.01) greater for the second examination (4.89) than for the first examination (3.63). Maximum lesion scores were greater in 24 horses, no different in 5 horses and less in 6 horses on the second examination. The difference in mean maximum lesion scores between examinations was greatest in horses age 2 years, increasing from 1.75 to 4.00 (P = 0.014). Lesions in the gastric glandular mucosa also were scored on a scale of 0 to 10 and there was no difference in mean lesion scores in the glandular mucosa between the first and second examinations (1.89 vs. 1.90). Lesion scores were compared for gender, racing history and medication with nonsteroidal anti-inflammatory drugs, systemic corticosteroid or ACTH, or frusemide within the previous 2 months. Except for racing history, there were no significant differences in mean lesion scores for squamous or glandular mucosa based on these comparisons, indicating that there was no effect of gender or medication history on ulcer severity in the horses of our study. Mean maximum gastric squamous mucosal lesion score was significantly (P < 0.01) greater in horses that had raced (4.51) than for horses that had not raced (2.36) in the 2 months before the endoscopic examination. There was no difference in mean glandular mucosal lesion scores between horses that had raced (1.93) compared to horses that had not raced (1.13).

Pulmonary edema associated with transient airway obstruction in three horses.

Pulmonary edema associated with transient airway obstruction was detected in 3 horses. The cause of obstruction was different in each horse, but after relief of the obstruction, clinical signs and radiographic abnormalities were indicative of pulmonary edema. In 2 of the 3 horses, pink frothy fluid was evident in the airways. The horses were treated with furosemide, nasal insufflation of O2, anti-inflammatory agents, and anti-biotics. Of the 3 horses examined, 1 horse died acutely, 1 horse recovered fully, and 1 developed pleuritis and was subsequently euthanatized.

Measurement of muscle surface capillary blood flow by laser Doppler flowmetry.

Muscle surface capillary blood flow was measured in the biceps femoris and lateral head of the triceps brachii muscles in six horses before and during halothane anesthesia by using laser Doppler flowmetry. During 90 minutes of anesthesia, muscle surface capillary blood flow was reduced to 20% to 40% of preanesthetic values. Muscle surface capillary blood flow tended to be lower in dependent muscles than in nondependent muscles, and this disparity was greater in the forelimbs than in the hind limbs.

Preliminary studies on the vascular anatomy of the equine superficial digital flexor tendon.

The vascular and microvascular anatomy of normal equine superficial digital flexor tendons was studied by dissection of vinyl-perfused specimens and by microangiography on high detail film. The presence of an extensive intratendinous vascular latticework was confirmed, and a 'nutrient artery' described closely associated with the accessory ligament of the superficial digital flexor tendon (proximal check ligament). Circumferential stripping of the paratenon from the tendon to eliminate afferent vessels was performed bilaterally in three horses and unilaterally in a fourth, followed by a treadmill training regimen. No resulting intratendinous lesions could be documented on gross post mortem and histological examination at three, 10, or 35 days post operatively. There was mild paratendinous proliferation in all instances. In one horse, four intratendinous ligatures were placed within the medial and lateral borders of the contralateral tendon to isolate further from its blood supply a 10 cm segment. Gross lesions at 35 days post operatively included a marked paratendinous response involving the entire 10 cm segment, and a darkened, soft focus within the core of the tendon. Histopathology and electron microscopy demonstrated focal degeneration. It was concluded that the blood supply of the normal equine superficial digital flexor tendon is primarily intratendinous, rather than paratendinous as previously thought. The lesions in one horse similar to those in naturally occurring tendinitis supported a vascular aetiology of the disease, and set the groundwork for studies aimed at the development of a clinically relevant tendinitis model.

Effects of cocaine on epicardial coronary artery reactivity in miniature swine after endothelial injury and high cholesterol feeding. In vivo and in vitro analysis.

The purpose of this study was to determine the effects of cocaine on vasoreactivity in the swine model. Eight miniature pigs underwent regional endothelial denudation of the left anterior descending coronary artery and were then fed a high cholesterol diet. Cross-sectional area (CSA) of coronary arteries was measured by quantitative angiography. Before denudation, intravenous cocaine (1, 3, and 10 mg/kg) decreased CSA of epicardial vessels by 19-44%. At 3 mo after the denudation, the percent reduction in CSA of the denuded vessels induced by the 10 mg/kg dose was significantly augmented compared to nondenuded vessels (59 +/- 5% vs. 48 +/- 4%, P less than 0.05). Under in vitro conditions where isometric force of isolated ring segments was measured, methoxamine (an alpha 1 agonist) or BHT-920 (an alpha 2 agonist) produced similar degrees of contraction of denuded and control vessels; however, cocaine in concentrations up to 3 x 10(-3) M did not produce contraction. These responses were unaffected by removal of the endothelium. Histologically, myointimal thickening was noted at the denuded site. The present study demonstrates an enhanced vasoreactivity of atherosclerotic coronary arteries to cocaine in vivo, the mechanism of which appears to be mediated by endogenous vasoactive substances rather than by a direct action of cocaine on vascular smooth muscle.

Effects of calcium channel blockers on coronary vasoconstriction induced by endothelin-1 in closed chest pigs.

The purpose of this study was to determine the effects of endothelin-1 on the coronary vascular bed of closed chest pigs. Endothelin-1 (3 to 30 pmol/kg body weight) was selectively administered into the left anterior descending coronary artery. Coronary blood flow and epicardial vessel diameter were measured by quantitative arteriography. Arterial pressure increased after a 30 pmol/kg dose and heart rate was not changed. Coronary blood flow and vessel diameter of the left anterior descending artery significantly decreased by 74% and 32%, respectively (p less than 0.01 versus control) after the 30 pmol/kg dose, whereas these variables modestly decreased in the left circumflex artery. Endothelin-1 in doses of 10 to 30 pmol/kg produced electrocardiographic ST segment elevation associated with decreased oxygen saturation of coronary sinus venous blood. Endothelin-induced coronary vasoconstriction was significantly inhibited after treatment with intravenous diltiazem (0.2 mg/kg, n = 6) or nifedipine (0.1 mg/kg, n = 5), but not after vehicle administration (n = 4). This study demonstrates that intracoronary administration of endothelin-1 causes significant myocardial ischemia through coronary vasoconstriction, which is inhibited by a calcium channel blocker. The data suggest that calcium influx into the smooth muscle cells appears to be involved at least in part in the mechanism of endothelin-induced coronary vasoconstriction in vivo.

Milrinone. A clinical trial in 29 dogs with moderate to severe congestive heart failure.

Milrinone, a positive inotropic drug with vasodilating properties, was administered at doses of 0.5 to 1 mg/kg orally twice daily to 29 dogs with moderate to severe congestive heart failure (CHF). Significant echocardiographic improvement in ventricular systolic function was observed after 3 days of administration of milrinone and at the patients' last echocardiographic observation (day 21 in 25 subjects, day 7 in 2 subjects, and day 3 in 2 subjects). Echocardiographic shortening fraction at the initial measurement had a median increase of 6.14% (P less than 0.001), and for the last observation a 2.83% increase (P less than 0.005). Most patients also showed improvement in their clinical signs as assessed by the veterinarian (72%) and by owner's evaluation (81%). No consistent problem or adverse reaction to milrinone was observed, except for a small number of clinically manageable ventricular dysrhythmias. Milrinone appears in this trial to be effective for the treatment of advanced CHF in dogs.

Antepartum evaluations of the equine fetus.

Measurements were made by real-time ultrasonography in 14 healthy mares to assess fetal growth and estimate newborn foal weights. Intrauterine fluid volumes were estimated and the placenta was measured and observed for maturational changes. The onset and incidence of echogenic particles in the allantoic fluid were recorded. In the second approach, baseline fetal heart rate, physiological rate variations and number, amplitude and duration of recorded accelerations were measured. Estimates of birth weights were within +/- 3.49 kg. Allantoic fluid was evident in all sonographic planes within the uterine cavity. Average vertical axis was 1.9 +/- 0.9 cm. The mean thickness of the ventrally located gravid uterine horn and allantochorion was 1.26 +/- 0.33 cm. No placental maturational changes were noted. Echogenic particles were observed in the allantoic fluid of all mares recorded within 10 days of foaling. Baseline fetal heart rate was 76 +/- 8 beats/min. Spontaneous fetal activity resulted in accelerations in fetal heart rate from 25 to 40 beats/min in amplitude and of 23-36 sec in duration. About 10 accelerations were observed in a 10-min period. In 17 clinical case mares, abnormal records included decreased fetal activity; lack of fetal growth; haemorrhage and fibrin-like tags in the allantoic fluid; fetal tachycardia, bradycardia, arrhythmia, and cardiac deceleration. We suggest that ultrasonic fetal measurements provide useful information with regard to the fetal condition, but additional variables are required for more reliable assessments of fetal stress and distress.

Echocardiographic detection of ventricular septal defects in large animals.

Ventricular septal defects in a foal, a 2-year-old filly, and 2 calves were demonstrated with M-mode and two-dimensional real-time echocardiography. The studies were performed with the animals unsedated, either standing or in lateral recumbency. Cardiac windows were located between the 4th and 7th intercostal spaces, approximately at the level of the olecranon. In each case, the septal defect was visualized high in the membranous portion of the interventricular septum. Defects were visualized by use of sector scanning or linear-array ultrasonic equipment, with transducer frequencies of 2.25 to 3.5 MHz.

Echocardiographic and clinical effects of milrinone in dogs with myocardial failure.

Milrinone is a recently synthesized bypyridine compound with positive inotropic and arteriolar dilating properties in persons and experimental animals. To examine the efficacy and safety of milrinone to treat myocardial failure in dogs, dogs with myocardial failure were selected from the patient populations of 3 veterinary hospitals. Progressively increased dosages of milrinone, from 0.05 to 1.0 mg/kg of body weight, were administered over 14 days, and cardiac responses, as determined by M-mode echocardiography, and clinical responses were recorded. An effective dosage of milrinone was identified for each dog and administered for 4 weeks to evaluate the stability of the cardiac response. A randomized blinded study of drug vs nondrug capsule or nondrug elixer (designated placebo) was performed at the end of 4 weeks to eliminate possible effects of investigator bias or spontaneous regression of the disease. The duration of drug effect was determined by evaluating echocardiographic measurements of left ventricular function for 12 hours after drug administration. Echocardiographic evaluation of left ventricular function improved in dogs given milrinone. The effective dosage was between 0.5 and 1.0 mg/kg. Tolerance to milrinone did not develop during the 4-week study. In dogs given placebo during the randomized blinded study, echocardiographic values decreased significantly. Dogs that were given milrinone remained echocardiographically stable. During the study, 6 dogs improved clinically, 5 remained the same, 1 had a decrease in exercise tolerance, 1 died of severe heart failure, and 1 died of hypoadrenocorticism. Ventricular tachydysrhythmia was exacerbated in 2 dogs, but was not treated.(ABSTRACT TRUNCATED AT 250 WORDS)

Endocarditis in six horses.

Six horses (five males) aged three months to fourteen years had endocarditis at necropsy. Two of the horses had a clinical diagnosis of valvular endocarditis with negative blood cultures. Single or complex valvular involvement was present in five horses. One horse had non-infectious thrombi associated only with the chordae tendineae. Mitral valves were affected in four horses, and aortic semilunar valves were affected in two. Infarcts had occurred in the kidneys and the myocardium of four horses. Bacteria were isolated postmortem from the valvular vegetations of two horses; Candida parapsilosis was isolated and demonstrated morphologically in a third horse.

Techniques and applications of transabdominal ultrasonography in the pregnant mare.

To establish the feasibility of utilizing high-frequency ultrasound to image equine fetal development transabdominally, in vitro and in vivo observations were made. Three fetuses retrieved from mares that died from various causes were scanned in vitro to establish fetal images from various orientations. A total of 50 mares ranging in age from 4 to 16 years and representing various breeds were scanned intermittently from 100 days of gestation to parturition. Fetal parts, amniotic fluid, placental membranes, and motion patterns could be reliably identified. Fetal heart rates decreased from 180 beats/min at 100 days' gestation to 60 to 80 beats/min from 2 weeks before parturition to term. Detection of fetal orientation, viability, and twin recognition represented practical applications of the technique.

Ultrasonography as an adjunct to pregnancy assessments in the mare.

Ultrasonographic detection of pregnancy was performed in 952 Thoroughbred mares. Characteristic images were obtained between 12 and 55 days after breeding. Twins in the same uterine horn as well as twins in opposite horns were imaged, and for the first few months of gestation appeared similar to single pregnancies. Growth curves as a function of time were developed, utilizing horizontal diameters of the blastocysts versus breeding dates. Comparisons between horizontal and vertical diameters demonstrated no appreciable differences when observed as a group. Growth curves derived from twins did not differ significantly from those for single pregnancies during the period we observed them. Ultrasonographic evaluations were valuable in substantiating mechanical destruction of one of the twin blastocysts immediately following the maneuver. Uterine artifacts such as endometrial and lymphatic cysts also were visualized and portrayed. Although these structures represented a source of false-positive results, they usually could be properly identified on the basis of their morphometric and growth characteristics.

Echocardiographic features of aortic valve endocarditis in a dog, a cow, and a horse.

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 consequences of aortic regurgitation observed by echocardiography were left ventricular dilation, diastolic fluttering of the mitral valve, premature closure of the mitral valve, and left ventricular hyperkinesia.

Diagnosis of cardiac lesions by contrast echocardiography.

Contrast M-mode echocardiography was utilized to study animals with congenital and acquired cardiac defects. Contrast was produced through the rapid injection of isotonic NaCl solution, the patient's blood, or indocyanine green dye into the circulation. Peripheral vein and intracardiac injections of contrast material were used to document ventricular septal defect, tetralogy of Fallot, atrial septal defect, and mitral valve regurgitation. The technique was safe and useful for both small and large animals.