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Background: Aortic rupture is more common in Friesians compared to Warmbloods, which might be related to differences in arterial wall composition and, as such, arterial wall stiffness (AWS). Currently, nothing is known about differences in AWS between these breeds. Objectives: Comparison of AWS parameters and noninvasive blood pressure between Friesians and Warmbloods. Animals: One hundred one healthy Friesians and 101 age-matched healthy Warmbloods. Methods: Two-dimensional and pulsed-wave Doppler ultrasound examination was performed of the aorta, common carotid artery, and external iliac artery to define local and regional AWS parameters. Regional aortic AWS was estimated using aortic-to-external iliac artery pulse wave velocity (PWVa-e) and carotid-to-external iliac artery pulse wave velocity (PWVc-e). Noninvasive blood pressure and heart rate were recorded simultaneously. Results: Systolic, diastolic, and mean arterial blood pressure and pulse pressure were significantly higher in Friesians compared to Warmbloods. No significant difference in heart rate was found. Most local AWS parameters (diameter change, compliance coefficient, distensibility coefficient) were significantly lower in Friesians compared to Warmbloods, indicating a stiffer aorta in Friesians. This difference could be confirmed by the regional stiffness parameters. A higher PWVa-e and PWVc-e was found in Friesians. For the cranial and caudal common carotid artery and external iliac artery, most local AWS parameters were not significantly different. Conclusions and clinical importance: Results indicate that aortic AWS differs between Friesian and Warmblood horses. Friesians seem to have a stiffer aorta, which might be related to the higher incidence of aortic rupture in Friesians.

Background: Atrial tachycardia including focal atrial tachycardia and macroreentrant atrial tachycardia (atrial flutter), are occasionally found in horses. Diagnosis, treatment and follow-up of these arrhythmias has been inadequately described. Objectives: To describe the findings on surface electrocardiography (ECG), intra-atrial electrogram recording and tissue Doppler imaging (TDI), the response to treatment by transvenous electrical cardioversion (TVEC), and TDI follow-up, of sustained atrial tachycardia in horses. Study design: Case series. Methods: Records from horses with sustained atrial tachycardia treated by biphasic TVEC at Ghent University were reviewed. Horses with atrial fibrillation were not included. Results: Seven horses with sustained atrial tachycardia were treated with TVEC. In six cases an exercise ECG was available and in 4 a 12-lead ECG had been recorded. The mean bias between atrial cycle length measured from a right atrial intra-atrial electrogram and from TDI ranged between -2 and 3 ms depending on the sampled region. All seven cases converted to sinus rhythm during the first TVEC procedure. TDI showed atrial contractile function recovery similar to cases that were treated for atrial fibrillation. One case developed atrial fibrillation 1 day after TVEC treatment, another case showed recurrence 8 years post conversion. The other five cases were still in sinus rhythm at 9 months - 5 years after TVEC. Main limitations: Due to the small number of patients, data on recurrence and follow-up of atrial recovery should be interpreted with caution. Since no invasive electrophysiology studies were performed, differentiation between focal atrial tachycardia and atrial flutter remains speculative. Conclusions: Treatment of focal atrial tachycardia or atrial flutter by TVEC has a very high success rate. Tissue Doppler imaging allows noninvasive measurement of atrial cycle length and suggests reduced atrial function after cardioversion. Long-term prognosis after cardioversion seemed similar compared to horses with atrial fibrillation, although early recurrence (

Background Aortic regurgitation (AR) may lead to left ventricular (LV) dilatation, cardiac arrhythmias and heart failure. Close follow-up of horses with AR is therefore paramount to detect onset of cardiac decompensation. The aim of this study was to examine whether two-dimensional speckle tracking (2DST) can be used to detect altered myocardial function in horses with chronic AR compared to control horses. Speckle tracking was performed on short axis and long axis images of the LV in 29 healthy Warmblood horses and 57 Warmblood horses with AR. Radial, circumferential and longitudinal strain, strain rate and displacement were measured for each segment separately and the average was calculated over all segments. Data generated from the apical segments were not included in the analysis. Results Radial (SR) and circumferential (SC) strain were significantly higher in horses with moderate AR (average SR 75.5 ± 24.3%, SC 19.3 ± 3.2%) but not in horses with severe AR (SR 65.5 ± 26.2%, SC 16.3 ± 3.5%), compared to control horses (SR 54.5 ± 18.0%, SC 16.8 ± 3.0%). Longitudinal strain did not show significant differences, but longitudinal displacement (DL) was larger in horses with moderate (average DL 29.5 ± 4.1 cm) and severe AR (DL 32.4 ± 6.1 cm) compared to control horses (DL 25.7 ± 4.0 cm), especially in the interventricular septum. Diastolic longitudinal strain rate was lower in early diastole in horses with severe AR (0.93 ± 0.18/s) compared to controls (1.13 ± 0.13/s). Conclusions 2DST is able to detect altered myocardial motion in horses with AR, which showed significantly higher radial and circumferential strain. Further research is needed to determine whether these findings contribute to a more accurate diagnosis and prognosis in clinical cases.

Introduction Homocysteine (HCY) is an amino acid produced from methionine metabolism. Plasma homocysteine concentrations ([HCY]p) are elevated (>13 μmol/L) in people with atrial fibrillation (AF) and can predict the recurrence of AF after cardioversion. This study aimed to validate a commercially available human HCY assay for use in horses to develop reference intervals for [HCY]p and compare [HCY]p in healthy horses and horses with AF. Animals Healthy horses (n = 27) and horses with AF (n = 55, 34 of which were cardioverted using transvenous electrical cardioversion). Materials and methods Blood samples were analysed for HCY using an automated enzyme-cycling assay (Homocysteine Cobas C, Integra, Roche) and creatinine (compensated Jaffe method). Assay linearity and precision were assessed, reference intervals calculated and [HCY]p and creatinine compared between groups. Results The assay was precise (coefficient of variation 1.6–4.3%, n = 10 repetitions) and provided linear results (r = 0.99 for spiked and natural samples) for a range of [HCY]p. The reference interval for [HCY]p was 1.5–7.8 μmol/L. The plasma concentration of homocysteine was 4.65 ± 1.5 μmol/L (mean ± standard deviation) in healthy horses and 4.65 ± 1.72 μmol/L in horses with AF (p=0.99); [HCY]p was not associated with recurrence of AF (n = 18, p=0.97). A weak, positive correlation between plasma creatinine and [HCY]p was detected (r = 0.295, p=0.008, r2 = 0.11). Conclusions This assay allows precise measurement of [HCY]p in horses. Unlike in people, [HCY]p is not increased in horses with AF and cannot predict AF recurrence. This might be due to differences in the underlying pathological mechanisms of AF development in people and horses.

Item does not contain fulltext BACKGROUND: Arrhythmias in horses may require long-term anti-arrhythmic therapy. Unfortunately, oral anti-arrhythmic drugs for use in horses are currently scarce. In human patients and small animals, sotalol, a beta-blocker with class III anti-arrhythmic properties, is often used for long-term treatment. OBJECTIVES: To determine the pharmacokinetics of sotalol at multiple oral dosages in unfasted horses, as well as the effects on electro- and echocardiographic measurements, right atrial and ventricular monophasic action potential (MAP) and effective refractory period (ERP). STUDY DESIGN: Placebo controlled, double-blinded experiment. MATERIALS AND METHODS: Six healthy, unfasted Warmblood horses were given either 0, 2, 3 or 4 mg/kg bodyweight (bwt) sotalol orally (PO) twice daily (bid) for 9 days in a randomised cross-over design. Echocardiography and surface electrocardiography were performed and plasma concentrations of sotalol and right atrial and right ventricular MAPs and ERPs were determined at steady-state conditions. Statistical analysis was performed using a repeated measures univariate analysis with post hoc Bonferroni corrections. RESULTS: Calculated mean steady-state plasma concentrations determined by nonlinear mixed-effect modelling were 287 (range 234-339), 409 (359-458) and 543 (439-646) ng/mL for 2, 3 and 4 mg/kg bwt sotalol PO bid respectively. Sotalol significantly increased the QT interval and ERPs, but, despite increasing plasma concentrations, higher dosages did not result in a progressive increase in QT interval or ERPs. Echocardiographic and other electrocardiographic measurements did not change significantly. MAP durations at 90% repolarisation were not significantly different during sotalol treatment. Besides transient local sweating, no side effects were noted. MAIN LIMITATIONS: Study size and ad libitum feeding of hay. CONCLUSIONS: Sotalol at a dose of 2, 3 and 4 mg/kg bwt PO bid increases the QT interval and ERP and might be a useful drug for long-term anti-arrhythmic therapy in horses.

Summary Diagnosis of caecal intussusception can be challenging. Transabdominal ultrasound is often used as a diagnostic tool in equine colic. Differentiation between caecocaecal and caecocolic intussusception might be useful in the decision process before surgery. The aims of this study were: 1) to assess the usefulness of ultrasound for diagnosis of intussusception and differentiation between caecocaecal and caecocolic intussusception; and 2) to determine survival to hospital discharge after surgery. Therefore, a retrospective case series (2009–2013) was performed of all colic cases with caecal intussusception (n = 60) confirmed at surgery or necropsy. In all horses, the intussusception could be visualised using ultrasound at admission. Caecocolic intussusception (n = 46) was much more common than caecocaecal (n = 14) intussusception and correct ultrasonographic differentiation between both types could be made in 92% of the cases. Ten horses (out of 14) diagnosed with caecocaecal intussusception underwent surgery, of which 8/10 (80%) were discharged, one horse (10%) was subjected to euthanasia during and one (10%) after surgery. Of the 28 (out of 46) operated horses with caecocolic intussusception, 17 (61%) survived to discharge, while 7 (25%) and 4 (14%) were subjected to euthanasia during and after surgery, respectively. Of all horses that underwent surgery, in 13/38 (34%) surgical reduction was possible, while 13/38 (34%) needed partial typhlectomy and 4/38 (11%) needed colostomy because of an irreducible intussusception. Survival to discharge after successful surgery was 12/13 (92%) when only reduction was performed, 11/13 (85%) if partial typhlectomy was needed and 2/4 (50%) after colostomy and partial typhlectomy. In conclusion, abdominal ultrasound is a useful tool in the diagnosis and differentiation of caecal intussusception. Survival to hospital discharge after successful surgery is good.

A twenty-four-year-old mare, which had been examined seven years earlier for mitral valve regurgitation and mild left sided cardiomegaly, was presented with tachycardia, profuse sweating and muscle fasciculations. Blood examination revealed an increased packed cell volume, metabolic acidosis, hypocalcemia, hyperglycemia and increased cardiac troponin I concentration. ECG revealed ventricular premature beats and monomorphic ventricular tachycardia followed by polymorphic ventricular tachycardia with R-on-T phenomenon. The horse was treated immediately with hypertonic solution followed by isotonic solution and calcium, but the general condition deteriorated within forty-five minutes after arrival. The horse was euthanized due to poor prognosis. On necropsy, a pheochromocytoma of the left adrenal gland was found. Although this horse had undergone a cardiovascular examination seven and one year prior to the onset of the clinical signs, no indications for a neoplastic process or symptoms of a pheochromocytoma were found at that time. Early diagnosis of pheochromocytoma is based on catecholamine mediated cardiovascular effects, blood examination, blood pressure measurement, rectal palpation and rectal ultrasound of the adrenal gland. Based on a retrospective analysis of echocardiographic images and measurements, no predisposing factors were found. In this article, the importance of including pheochromocytoma as a differential diagnosis is highlighted, especially in older horses with acute polymorphic ventricular tachycardia, sweating, muscle tremors and signs of acute abdominal pain.

Diagnosis of steatitis can be challenging due to nonspecific clinical signs and ultrasonography might be a useful aid for making a diagnosis. The objective of this retrospective clinical case study was to describe history, clinical signs, ultrasonographic findings, treatment and outcome in equids with steatitis. The medical records of all equids presented to the Department of Large Animal Internal Medicine, Ghent University between January 2008 and December 2015 were reviewed retrospectively to identify horses suffering from steatitis. A total of 20 cases with steatitis were reviewed. History included dullness, recumbency, decreased appetite and weight loss. Fever, ventral oedema, stiff/painful gait and a painful neck were found. Low haematocrit, low vitamin E and selenium and increased levels of creatinine kinase and particularly lactate dehydrogenase were almost consistent findings. On ultrasound, ventral oedema was found. Ventral extraperitoneal, perirenal, mesenteric, coronary and caudal mediastinal fat showed homogenously increased echogenicity. The ventral extraperitoneal fat in particular was surrounded by oedema or free fluid. Increased amounts of abdominal, thoracic and pericardial fluid were often found. Fat biopsies were taken in the neck, or from the ventral extraperitoneal fat in the ventral flank. Steatitis was confirmed in all horses where a fat biopsy was taken (n = 13). Treatment consisted of selenium and vitamin E (intramuscular injection followed by oral treatment) supplementation and anti-inflammatory treatment (dexamethasone or prednisolone parenteral or oral) for at least 1-4 weeks. A total of 15 animals (75%) survived. Full recovery took about 2-6 months. In conclusion, steatitis is an uncommon disease in young horses usually seen during winter. It may be underdiagnosed because of nonspecific clinical signs. Ultrasonography is a useful aid for the diagnosis of yellow fat disease based upon the increased echogenicity of ventral extraperitoneal, perirenal, mesenteric, coronary and caudal mediastinal fat and increased amount of surrounding fluid.

Summary 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.

Excellence in either sprinting or endurance running requires specific musculo-skeletal characteristics of the legs. This study aims to investigate the morphology of the leg of sprinters and endurance runners of Caucasian ethnicity. Eight male sprinters and 11 male endurance runners volunteered to participate in this cross-sectional study. They underwent magnetic resonance imaging and after data collection, digital reconstruction was done to calculate muscle volumes and bone lengths. Sprinters have a higher total upper leg volume compared to endurance runners (7340 vs 6265 cm3). Specifically, the rectus femoris, vastus lateralis, and hamstrings showed significantly higher muscle volumes in the sprint group. For the lower leg, only a higher muscle volume was found in the gastrocnemius lateralis for the sprinters. No differences were found in muscle volume distribution, center of mass in the different muscles, or relative bone lengths. There was a significant positive correlation between ratio hamstrings/quadriceps volume and best running performance in the sprint group. Sprinters and endurance runners of Caucasian ethnicity showed the greatest distinctions in muscle volumes, rather than in muscle distributions or skeletal measures. Sprinters show higher volumes in mainly the proximal and lateral leg muscles than endurance runners.

This report describes a rare case of an aorto-cardiac fistula in a six-year-old French Warmblood mare presented with atrial fibrillation, decreased performance, ventral oedema, bounding arterial pulsation and pathological jugular venous pulse. A 2.7-cm-diameter fistula connected the right aortic sinus of Valsalva to the right atrium. Atrial fibrillation was likely due to volume overload of the right heart due to left-to-right shunting. The horse was treated by percutaneous transcatheter closure of the fistula delivered under general anaesthesia using a transarterial approach. The operation was initially successful, and clinical signs of congestive heart failure improved immediately. However, the device dislodged six days after procedure, and the general condition of the horse deteriorated quickly. A second closure attempt to deliver the occluder using a transvenous approach in the standing horse failed, and the horse was eventually euthanized. Procedural aspects and several possible risk factors for device dislodgement are discussed.

Background Ultra-high-density cardiac mapping allows very accurate characterisation of atrial and ventricular electrophysiology and activation timing. Objective To describe the technique and evaluate the feasibility of magnetic electro-anatomical mapping of the equine heart. Study design In vivo experimental method development. Methods A mapping system using an 8.5F bidirectional deflectable catheter with a deployable mini-basket (3-22 mm) containing 64 electrodes divided over eight splines was evaluated. Based upon predefined beat acceptance criteria, the system automatically acquires endocardial electrograms and catheter location information. Electro-anatomical maps were acquired from four horses in sinus rhythm under general anaesthesia. Results All endocardial areas within each chamber could be reached. Access to the left atrium required the use of a deflectable sheath. With the exception of the left atrial map of horse 1, all four chambers in all four horses could be mapped. Optimisation of the beat acceptance criteria led to a reduction in manual correction of the automatically accepted beats from 13.1% in the first horse to 0.4% of the beats in the last horse. Main limitations Only a limited number of horses were included in the study. Conclusion Ultra-high-density 3D electro-anatomical mapping is feasible in adult horses and is a promising tool for electrophysiological research and characterisation of complex arrhythmias.

Background In human medicine, local and regional arterial wall stiffness (AWS) parameters are routinely used to assess the vascular health. In horses, information regarding reproducibility of ultrasonographically derived AWS parameters is lacking. Objectives To evaluate the inter-day and inter-observer and intra-observer measurement variability of both local and regional AWS parameters in horses. Study design Experimental study. Methods In 10 healthy, adult Warmblood horses, B-, M-mode and pulsed-wave Doppler ultrasound images were collected on two different days from aorta, cranial and caudal common carotid arteries and external iliac artery. Heart rate and noninvasive blood pressure were recorded simultaneously. From blinded data, diastolic and systolic vessel lumen areas and diameters were measured from B/M-mode images and the velocity of the pressure wave was determined by pulsed-wave Doppler spectra. From each horse, one examination was measured again by the same observer and by a second, independent observer. Local and regional AWS parameters were calculated and inter-day and inter-observer and intra-observer measurement coefficient of variation (CV) were assessed. Results Low CV was found for both arterial diameter and lumen area measurements. Moderate to high CV was found for local AWS parameters, while regional AWS parameters had low CV. Main limitations The number of horses investigated was too low to obtain reference values. The inter-operator variability was not evaluated. Conclusions Our results show good reproducibility of aortic, carotid and external iliac artery diameter and area measurements using both B- and M-mode ultrasonography. Nevertheless, the variability of the derived local AWS parameters was relatively high. Therefore, local AWS parameters might be less suitable for follow-up studies, although they might be useful for population studies. On the other hand, regional AWS parameters showed low CV, making them valuable for both follow-up and population studies.

Background: The number of atrial premature depolarisations (APDs) is a known risk factor for atrial fibrillation (AF) recurrence in humans. Objectives: To evaluate if the number of APDs over a 24-h period 5 days post cardioversion predicts AF recurrence within 1 year in horses, taking the multifactorial nature of AF into account. Study design: Retrospective case series. Methods Eighty horses met these inclusion criteria: first AF episode, no AF recurrence within 5 days post cardioversion, cardioversion by transvenous electrical cardioversion (TVEC), 24-h ECG recording and echocardiographic examination 5 days post cardioversion, no antiarrhythmic treatment during the ECG recording and follow-up of minimum 1 year. To compare the APD burden between the recurrence and non-recurrence group a Mann-Whitney U test was used. A multivariable survival model was built to identify additional risk factors for AF recurrence. Results: The patient population mainly consisted of Warmbloods (93%). Twenty-six horses (33%) experienced AF recurrence within 1 year. The number of APDs (median [range]) was significantly higher (P = 0.01) in the recurrence group (15 [1-152]) compared with the non-recurrence group (7 [0-304]). In the multivariable survival model, APDs >= 25/24 h (hazard ratio [HR] 2.9, 95% confidence interval [CI] 1.2-6.8, P = 0.02), mitral regurgitation (HR 8.6, 95% CI 2.6-28.9, P

Recently, ultrasound tissue characterization (UTC) was introduced as a reliable method for quantification of tendon structure. Despite increasing publications on the use of UTC, it is striking that there is a lack of normative data in active adolescents. Therefore, the aim of this study was to provide normative values of the Achilles tendon as quantified by UTC. Seventy physiotherapy students (26 male and 44 female students) with no history of Achilles tendon injuries were recruited. The Achilles tendons were scanned with UTC to characterize tendon structure. This study demonstrated that Achilles tendons of active, healthy adolescents contained 54.6% echo type I, 42.8% echo type II, 2.2% echo type III, and 0.3% echo type IV at midportion. The comparison between insertion and midportion of the tendon showed more echo type II at insertion (P

Background The electrocardiographic differentiation between atrial (APDs) and ventricular (VPDs) premature depolarizations is important. P wave prematurity and normal QRS and T wave morphology generally are used as discriminating criteria for APDs. Hypothesis/Objectives The aim of this study was to determine whether P, Q, R, S, and T wave amplitude, PQ interval, QRS and P wave duration and P and T wave morphology differ between APDs and sinus beats. To determine the relationship between the RR coupling interval and the change in S wave amplitude between sinus beats and APDs. Methods Case–control study. From a modified base-apex configuration of 30 horses with APDs at rest, sinus beat and APD associated preceding RR interval, P, PQ and QRS duration and P, R, S, and T wave amplitudes were measured. Linear mixed models and logistic regression were used to determine the effect of APDs on the ECG variables studied. Results In comparison to sinus beats, APDs were associated with a significant (P < .001) change in P amplitude (−0.03 ± 0.01 mV) and increase in S (0.20 ± 0.02 mV) and T (0.08 ± 0.03 mV) amplitude. PQ (−20.3 ± 5.2 ms) and RR (−519 ± 14 ms) interval and P duration (−21.1 ± 3.0 ms) decreased (P < .001). APDs were significantly associated with a singular positive P wave (OR: 11.0, P < .001) and were more likely to have a monophasic positive T wave (OR: 9.2, P < .001). A smaller RR coupling interval was associated with an increased relative difference in S amplitude (P < .01). Conclusions Atrial premature depolarizations may lead to changes in QRS and T wave morphology. Knowledge of these changes is important to avoid interpreting certain APDs as VPDs.

Reasons for performing study: Right ventricular (RV) function is scarcely described in horses. Objectives: To establish reliable echocardiographic measurements of right heart size and function in horses. Study design: Descriptive study in healthy horses. Methods: Ten healthy untrained adult trotter horses underwent repeated echocardiography performed by 2 sonographers from right and left parasternal standard and nonstandard views. Nonstandard views included a right parasternal view focused on the right atrium, left parasternal long-axis pulmonary artery view, left parasternal long-axis view focused on the right ventricle including anatomical M-mode of tricuspid annular motion and left parasternal pulsed wave Doppler recording of pulmonary flow. During off-line analysis, 2 observers performed two-dimensional, M-mode, pulsed wave Doppler, tissue Doppler imaging (TDI) and two-dimensional speckle tracking (2DST) measurements of RV size and function. Acquisition and measurement variability were assessed by calculating coefficients of variation (CV) from one-way repeated measures analyses of variance. The degree of variability was classified as low (CV 25%). Results: Most two-dimensional and M-mode measurements of RV, right atrial and pulmonary artery size showed low variability. The two-dimensional, M-mode and pulsed wave Doppler measurements of RV function showed a low to moderate variability. Right ventricular functional measurements by 2DST showed low variability, except for segmental strain rate. Right ventricular functional measurements by TDI showed a low to high variability, with a lower variability for timing than for peak measurements and a lower variability for velocity compared with deformation measurements. Conclusions: Right heart size and function can be assessed with low variability in horses.

Background Heart rate variability (HRV) parameters, and especially RMSSD (root mean squared successive differences in RR interval), could distinguish atrial fibrillation (AF) from sinus rhythm(SR) in horses, as was demonstrated in a previous study. If heart rate monitors (HRM) automatically calculating RMSSD could also distinguish AF from SR, they would be useful for the monitoring of AF recurrence. The objective of the study was to assess whether RMSSD values obtained from a HRM can differentiate AF from SR in horses. Furthermore, the impact of artifact correction algorithms, integrated in the analyses software for HRV analyses was evaluated. Fourteen horses presented for AF treatment were simultaneously equipped with a HRM and an electrocardiogram (ECG). A two-minute recording at rest, walk and trot, before and after cardioversion, was obtained. RR intervals used were those determined automatically by the HRM and by the equine ECG analysis software, and those obtained after manual correction of QRS detection within the ECG software. RMSSD was calculated by the HRM software and by dedicated HRV software, using six different artifact filters. Statistical analysis was performed using the Wilcoxon signed-rank test and receiver operating curves. Results The HRM, which applies a low level filter, produced high area under the curve (AUC) (> 0.9) and cut off values with high sensitivity and specificity. Similar results were obtained for the ECG, when low level artifact filtering was applied. When no artifact correction was used during trotting, an important decrease in AUC (0.75) occurred. Conclusion In horses treated for AF, HRMs with automatic RMSSD calculations distinguish between AF and SR. Such devices might be a useful aid to monitor for AF recurrence in horses. Electronic supplementary material The online version of this article (10.1186/s12917-018-1650-6) contains supplementary material, which is available to authorized users.

Background: Based on its pharmacokinetic profile and electrophysiological effects in healthy horses, sotalol potentially could be used as a long-term PO antiarrhythmic drug in horses. Objectives: To evaluate the effect of sotalol on heart rate (HR), QT interval, atrial fibrillatory rate, and success of cardioversion in horses with naturally occurring chronic atrial fibrillation (AF). Animals: Twenty-eight horses referred for transvenous electrical cardioversion of AF were treated with 2 mg/kg sotalol PO q12h for 3 days before cardioversion, and 13 horses underwent the same protocol without sotalol administration. Methods: Retrospective study. Before and after sotalol or no treatment, the HR was measured at rest and during an exercise test. The QT interval and atrial fibrillation cycle length (AFCL) were measured at rest using tissue Doppler velocity imaging. Results: In the control group, no significant differences were found between the 2 examinations. In the sotalol group, the HR at rest and during exercise was significantly lower after sotalol treatment, whereas the QT interval and AFCL measured by tissue Doppler increased significantly. Cardioversion to sinus rhythm was achieved in 25/28 horses in the sotalol group and all horses in the control group, but the median number of shocks and energy at cardioversion were significantly lower in the sotalol group. Conclusions and Clinical Importance: In horses with AF, sotalol administration results in class III antiarrhythmic effects and -blocking activity, with moderate HR reduction during exercise.

Although cardiac troponin T (cTnT) assays have been used to detect myocardial damage in horses, a cTnT assay has not been analytically validated, to our knowledge. The aims of this study were to estimate the precision of a high-sensitivity cTnT assay in horses and determine the effect of hemolysis on the measured cTnT concentration. Serum samples from horses were mixed in 3 different pools. Pool 1 consisted of samples from 3 healthy horses, pool 2 from 6 horses with heart failure or atypical myopathy, and pool 3 from 10 horses with atypical myopathy. The within- and between-run coefficients of variation were determined for each pool. Pools 2 and 3 were diluted to estimate linearity. To study the influence of sample hemolysis, serum was collected from 4 horses with a high cTnT concentration, in which hemolysis was mechanically induced. In addition, ethylenediamine tetra-acetic acid blood tubes were collected from 3 other horses, from which hemolysate was prepared and added to plasma at different concentrations. The within- and between-run coefficients of variation of all pools were

Brain natriuretic peptide (BNP) is used in human medicine for the diagnosis of congestive heart failure. Since BNP is species-specific and no equine assay is available, BNP has never been determined in horses. Because there is more than 90% homology between porcine and equine BNP, a porcine BNP enzyme-linked immunoassay (ELISA) was used in the present study to measure BNP in plasma of healthy horses (group 1; n=20), horses with cardiac disease without (group 2a; n=8) and with atrial dilatation (n=8), ventricular dilatation (n=1) or both (n=1) (group 2b; n=10). Samples were stored at -20 degrees C and -80 degrees C to study the influence of storage temperature. No significant differences were found between the BNP concentrations of group 1 (77.79; 37.20-513.36 pg/mL), group 2a (52.02; 24.69-268.37 pg/mL) or 2b (94.73; 42.88-470.66 pg/mL). Samples stored at -80 degrees C showed significantly (72.19, 24.69-513.36 pg/mL; P=0.001) higher concentrations than samples stored at -20 degrees C (47.35, 24.69-430.60 pg/mL). In this pilot study, it is suggested that the porcine BNP assay does not allow accurate detection of equine BNP. An equine specific BNP assay should be developed to study BNP concentrations in horses.

Background: Different cardiac troponin I (cTnI) assays give different results. Only 1 manufacturer has marketed troponin T (cTnT) assays. Therefore, cTnT often is preferred for detection of myocardial infarction in human patients. Studies of cTnT in horses are limited. Objectives: To compare a cTnI and a high-sensitive cTnT assay (hs-cTnT) in horses. Animals: Cardiac troponin I and cTnT were determined in 35 healthy horses (group 1), 23 horses suspected to have primary myocardial damage (group 2a), and 41 horses with secondary myocardial damage caused by structural heart disease (group 2b). Methods: All cTnI samples were analyzed at laboratory A (limit of detection [LOD]: 0.03 ng/mL), whereas cTnT samples were analyzed at 2 laboratories with the same hs-cTnT assay (laboratory B, LOD: 10.0 pg/mL; laboratory C, LOD: 4.0 pg/mL). Results: The median cTnI concentration in group 2a (0.90 ng/mL; range, 0.03–58.27 ng/mL) was significantly higher (P < .001) than in group 1 (0.03 ng/mL; range, 0.03–0.09 ng/mL) or group 2b (0.05 ng/mL; range, 0.03–30.92 ng/mL), and the optimal cut-off for detection of primary myocardial damage was 0.095 ng/mL (sensitivity: 90.5%, specificity: 100%). Using an LOD of 10.0 pg/mL for all cTnT samples, a cut-off value of 10.5 pg/mL was found, but sensitivity was low (42.9%). When only samples analyzed at laboratory C (n = 58) were included, a cut-off of 6.6 pg/mL was found (sensitivity: 81%, specificity: 100%). Conclusions and Clinical Importance: Despite large quantitative differences, cTnI and cTnT are both useful for detection of myocardial damage in horses.

A 15-year-old Warmblood mare, at 8 months of gestation, was presented to the Ghent University Faculty of Veterinary Medicine for evaluation of suspected stage one labor. Transrectal ultrasonography revealed no clear signs of placentitis or stage one labor. The combined thickness of uterus and placenta was 11 mm and the cervix was closed. Twin pregnancy was suspected by transabdominal ultrasonography but could not be confirmed with certainty. An electrocardiogram (ECG) was recorded from the mare's abdominal wall to register a fetal ECG. To confirm twin pregnancy, registration of both fetal ECGs simultaneously on the same ECG trace was attempted. Twelve different electrode configurations were used. In 11 recordings, one fetal ECG was visible. Only one specific right-sided electrode configuration showed both fetal ECGs at the same time, which confirmed twin pregnancy. Although electrocardiographic diagnosis of a twin pregnancy in a mare is possible, this case highlights the need for multiple electrode configurations and the high likelihood of false negatives.

Background: In human and veterinary medicine, monophasic action potential (MAP) analysis and determination of local refractory periods by contact electrode technique gives valuable information about local cardiac electrophysiological properties. It is used to investigate dysrhythmias and the impact of drugs on the myocardium. Precise measurement of total MAP duration is difficult, therefore the MAP duration is usually determined at a repolarization level of 90% (APD90). Until now, no studies are published about the feasibility of this technique in the standing non-sedated horse. In 6 healthy Warmblood horses, on two different days, an 8F quadripolar contact catheter was passed through a jugular introducer sheath and placed under ultrasound guidance at the level of the intervenous tubercle or right atrial free wall (RA), and in the right ventricular apex (RV) to record the MAP. The MAP amplitude and APD90 were measured at a resting sinus rhythm (heart rate of 30-42 bpm) and at pacing cycle lengths (PCL) of 1000 and 600 ms. The effective refractory period (ERP) was determined at PCL of 1000 and 600 ms. Results: The overall mean (+/- SD) APD90 (rest), APD90 (1000) and APD90 (600) were 263 +/- 39 ms, 262 +/- 41 ms, 236 +/- 47 ms for the RA and 467 +/- 23 ms, 412 +/- 38 ms, 322 +/- 29 ms for the RV. The mean ERP1000 and ERP600 were 273 +/- 24 ms and 256 +/- 22 ms for the RA and 386 +/- 40 ms and 293 +/- 30 ms for the RV. The measurement variability for the amplitude, APD90 and ERP measurements in the RA ranged between 36 and 44, 9-22 and 7-8%, respectively. The measurement variability for the amplitude, APD90 and ERP measurements in the RV ranged between 49 and 66, 6-7 and 10-12%, respectively. Conclusions: RA and RV MAP duration and ERP can be obtained by a contact electrode in standing non-sedated horses. The measurement variability varies with catheter location.

Background Aortic regurgitation (AR) can have an important clinical impact and in some cases leads to left ventricular (LV) failure. Tissue Doppler imaging (TDI) is an echocardiographic technique that has been used in horses to detect LV dysfunction. Objectives To examine whether TDI detects changes in radial myocardial wall motion in horses with AR compared with control horses. Study design Case-control study. Methods Echocardiography was performed in 30 healthy Warmblood horses and 34 Warmblood horses with AR, subdivided in groups with mild, moderate or severe AR. TDI measurements were performed on six segments of the short-axis images of the LV myocardial wall. Myocardial wall motion was evaluated by measuring velocity and deformation during isovolumetric contraction, systole, early and late diastole. Timing of different events was also measured. Results In most segments, a significantly higher systolic myocardial velocity was found in horses with AR compared with controls. Horses with AR also had higher late diastolic velocity, although the difference was not significant in all segments. TDI measurement of timing intervals demonstrated less difference between groups. Main limitations There was a significant difference in age between the control group and horses with AR, which may confound the results. The assessment of AR severity was based on subjective criteria as there is no gold standard. Conclusions TDI showed significant differences in radial systolic and late diastolic myocardial velocity in horses with AR. This could indicate an altered LV function in these horses, but further research is needed to investigate the prognostic value of these measurements.

A 2 years and 11 months old Belgian draught horse stallion with a membranous ventricular septal defect, severe aortic regurgitation, mild left ventricular enlargement and ventricular premature depolarisations was anaesthetised to perform open castration. A balanced anaesthetic approach, involving intravenous use of romifidine (80 µg/kg), morphine (0.1 mg/kg) and lidocaine (1 mg/kg) for premedication, followed by induction of anaesthesia with ketamine (2.2 mg/kg) and midazolam (0.06 mg/kg) and maintenance with isoflurane, lidocaine CRI (50 µg/kg/min) and intratesticular lidocaine 2 per cent (10 ml in each testicle) was used to optimise the cardiovascular stability and enhance the safety of the procedure. A multimodal analgesic approach was provided, aiming to reduce the amount of isoflurane required to maintain a surgical plane of anaesthesia. A smooth and uneventful recovery was obtained. The present case report describes an anaesthetic protocol that could be applied in similar cases.

Summary Reasons for performing study Shortening of atrial fibrillation cycle length (AFCL) is a marker of atrial electrical remodelling due to atrial fibrillation (AF). Objectives To investigate the effect of administration of detomidine on AFCL measured invasively from an intra-atrial electrogram (AFCLEGM) and noninvasively by tissue Doppler imaging (AFCLTDI). We hypothesised that detomidine would have no effect on AFCL but would improve the ease of TDI measurements and facilitate noninvasive AFCL determination. Study design Prospective clinical study. Methods Measurements were performed before and after i.v. administration of 7.5 μg/kg bwt detomidine in 33 episodes of AF in 32 horses (582 ± 64 kg bwt, 10 ± 3 years old) referred for electrical cardioversion. The AFCLEGM was measured from a right atrial intracardiac electrogram. The AFCLTDI was measured from atrial colour tissue velocity curves in 5 atrial wall regions. Mean AFCLEGM and AFCLTDI without and with sedation were compared using a repeated-measures linear mixed model with Bonferroni correction for multiple comparisons and calculation of the Bland–Altman mean bias and limits of agreement between AFCLEGM and AFCLTDI. Results The mean AFCL was significantly increased after sedation, but this increase was very small (mean difference +4 ms). For AFCLTDI measurements, sedation significantly improved the quality of the atrial myocardial velocity curves and the number of AF cycles that could be measured per cardiac cycle. The Bland–Altman bias between AFCLEGM without sedation and AFCLTDI with sedation ranged from -18 to +15 ms depending on wall region. Bland–Altman limits of agreement were similar between AFCLEGM without sedation and AFCLTDI without and with sedation. Therefore, noninvasive AFCLTDI measurements with sedation can be used to estimate the atrial fibrillatory rate. Conclusions Sedation facilitates noninvasive AFCL measurements but causes a slight increase in AFCL. Noninvasive AFCL measurements can be used as an indicator of atrial electrical remodelling, to study AF pathophysiology and to investigate the effect of anti-arrhythmic drugs.

In deze casus wordt een geval van gelokaliseerde steatitis ter hoogte van het perivaginale vetweefsel na dystokie bij een merrie gerapporteerd. Hoewel de merrie post partum aanvankelijk goed herstelde, kende dit geval enkele dagen later toch een fatale afloop. Tijdens de tweede consultatie werd er op het vaginale onderzoek in de wand van de vagina beiderzijds een knobbelig aanvoelende verhevenheid waargenomen. De intravaginale opening van deze verhevenheden ging gepaard met een etterige uitvloei die geelbruine brokjes necrotisch vetweefsel bevatte. Later werden op de lijkschouwing ook steatitis ter hoogte van de ophangbanden van de urineblaas en een blaasruptuur vastgesteld, hetgeen wellicht gezorgd heeft voor de snelle evolutie van de klinische symptomen. Algemeen worden er twee steatitisvormen onderscheiden: de gelokaliseerde en de gegeneraliseerde vorm. Bij de gelokaliseerde vorm wordt slechts één vetdepot aangetast, terwijl bij de gegeneraliseerde vorm meerdere vetdepots in het ziekteproces betrokken zijn. Gelokaliseerde steatitis ter hoogte van het perivaginale vetweefsel werd nog niet eerder beschreven bij het paard.

Background : Atrial fibrillation (AF) cycle length (CL) and atrial size have been used in humans to characterize electrical and structural remodeling to predict outcome of cardioversion of AF and risk for AF recurrence (rAF). Hypothesis : Atrial fibrillation cycle length can be determined in horses with AF, and AFCL and atrial size are related to risk for rAF. Animals : Eighteen horses with naturally occurring AF that were successfully converted to sinus rhythm (SR) by transvenous electrical cardioversion (TVEC). Methods : Prospective study. Horses with severe valvular regurgitation, left atrial enlargement, or that required sedation for catheter placement were excluded. In all horses intra-atrial electrograms were recorded and estimated AF duration and echocardiographic parameters were determined before TVEC. The follow-up time was 1year after TVEC. Results : Atrial fibrillation cycle length could be determined in all horses. The AFCL and the shortest 5th percentile (p5) AFCL in horses with rAF (n=6 or 33%) were (mean +/- SD) 157 +/- 28 and 134 +/- 24milliseconds, respectively, and in those maintaining SR (n=12 or 67%) 166 +/- 13 and 141 +/- 13milliseconds, respectively. Significant parameters to predict rAF were (1) the ratios of the p5AFCL to the left atrium (LA) sizes corrected to the size of aorta (AO) and (2) LA sizes corrected to the size of AO. Conclusions and Clinical Importance : Before TVEC, assessment of LA size and atrial electrophysiologic characteristics might help to identify horses at increased risk for AF recurrence.

Background: In human medicine, arterial wall stiffness (AWS) parameters are calculated from ultrasonographically measured diastolic (DD) and systolic arterial diameter (SD) in order to assess vascular health. In horses, information regarding reproducibility of ultrasonographic measurements of arterial diameters is lacking. Objectives: To evaluate the inter-day, inter-observer and intra-observer variability of ultrasonographic arterial diameter measurements in horses. Study Design: Prospective study. Methods: In ten healthy, adult Warmblood horses, ultrasound images were recorded on two different days from aorta (B-mode), common carotid and femoral artery (B-mode and M-mode). In addition, heart rate and non-invasive blood pressure were recorded simultaneously. From blinded data, DD and SD were measured over nine cardiac cycles from B/M-mode images of both days, and from each horse, one exam was measured again by the same observer and by a second, independent observer. Inter-day, inter-observer and intra-observer coefficients of variation were calculated. Carotid and femoral diameter measurements from M-mode were compared with diameters derived from measured areas on B-mode images using a paired t-test. Results: There was no significant difference in heart rate or blood pressure between both days. Mean B-mode DD and SD (±standard deviation) for aorta, carotid and femoral artery were 59.8±4.1mm and 66±4.4mm, 11.7±1.1mm and 12.3±1.2mm, and 12.8±1.1mm and 13.2±1.0mm, respectively. The latter were not significantly different from M-mode measurements. For DD and SD from M and B-mode images of all three arteries, inter-day (4-9%), inter-observer (1-3%) and intra-observer (1-2%) variability was low. Main Limitations: A larger group of healthy horses must be examined to define reference ranges for arterial diameters. Conclusions: Our results show good reproducibility of aortic, carotid and femoral diameter measurements using both B- and M-mode ultrasonography, suggesting these are potentially useful variables for assessing AWS in horses.

Cardiac biomarkers such as troponins and natriuretic peptides are routinely used in human medicine for the evaluation of myocardial damage and heart failure. Recently, these markers have also been introduced in veterinary medicine. Comparison between human and equine cardiac biomarker studies show i

Summary Reasons for performing study Atrial fibrillation cycle length (AFCL) is an indicator of atrial electrical remodelling during atrial fibrillation (AF). Objectives To compare AFCL measured invasively from an intra-atrial electrogram (AFCLEGM) with AFCL measured noninvasively by atrial colour tissue Doppler imaging (AFCLTDI). Study design Prospective descriptive clinical study. Methods Measurements were performed in 31 episodes of AF or flutter in 29 horses (588 ± 61 kg bwt, 9 ± 3 years old) admitted for transvenous electrical cardioversion. The AFCLEGM was measured from an intracardiac electrogram using a bipolar sensing/pacing electrode inserted into the right atrium. The AFCLTDI was measured from atrial colour tissue velocity curves in the following 5 regions: 1) left atrial free wall from a right parasternal 4-chamber view, 2) left atrial free wall from a short-axis view, 3) left atrial free wall from a left parasternal long-axis view, 4) interatrial septum, and 5) right atrial dorsal wall near the tuberculum intervenosum. The AFCLEGM and AFCLTDI from the 5 regions were compared using a one-way repeated-measures ANOVA with Bonferroni correction for multiple comparisons and calculation of the Bland-Altman mean bias and limits of agreement of AFCLEGM and AFCLTDI. Results The AFCLEGM was 161 ± 18 ms in 29 AF episodes. Two horses showed atrial flutter and had an AFCLEGM of 244 and 324 ms. The mean bias between AFCLTDI and AFCLEGM ranged from -18 to +9 ms depending on the atrial wall region. The AFCLTDI was significantly shorter in the left atrial free wall from the right parasternal 4-chamber view and short-axis view than in the other regions (P

Objective—To compare the feasibility and repeatability of tissue Doppler imaging (TDI) for quantification of radial left ventricular (LV) velocity and deformation from different imaging planes and to correlate cardiac event timing data obtained by TDI to M-mode and pulsed-wave Doppler-derived time intervals in horses. Animals—10 healthy adult horses. Procedures—Repeated echocardiography was performed by 2 observers from right and left parasternal short-axis views at papillary muscle and chordal levels. The TDI measurements of systolic and diastolic velocity, strain rate, strain peak values, and timing were performed in 8 LV wall segments (LV free wall and interventricular septum from right parasternal views; left and right region of LV wall from left parasternal views). The inter- and intraobserver within- and between-day variability and measurement variability were assessed. The correlation between TDI-based measurements and M-mode and pulsed-wave Doppler-based time measurements was calculated. Results—TDI measurements of velocity, strain rate, and strain were feasible in each horse, although deformation could often not be measured in the LV free wall. Systolic and diastolic time intervals could be determined with low to moderate variability, whereas peak amplitude variability ranged from low to high. The TDI-based time measurements were significantly correlated to M-mode and pulsed-wave Doppler measurements. Conclusions and Clinical Relevance—TDI measurements of radial LV velocity and deformation were feasible with low to moderate variability in 8 LV segments. These measurements can be used for evaluating LV function in further clinical studies.

The disproportionate rise of pulmonary artery pressure compared to systemic blood pressure during exercise can lead to detrimental right ventricular remodelling in endurance athletes. Horses may act as an extreme model of these athletic cardiovascular adaptations, as they show a three fold increase in pulmonary pressures during exercise. Right ventricular function was examined in ten healthy horses using post-exercise and pharmacological stress echocardiography in a randomised cross-over design. Exercise testing was performed on a treadmill while pharmacological testing was performed using an atropine-dobutamine infusion. Heart rate, systemic blood pressure and cardiac output during echocardiography were similar post-exercise compared to maximal pharmacological stress. Systolic pulmonary artery pressure was significantly higher during the exercise test (121±15mmHg) and during immediate post-exercise echocardiography (93±10mmHg) compared to maximal pharmacological stress (69±12mmHg). Right ventricular diameters as well as the ratio of systolic right to left ventricular area were higher post-exercise. Right ventricular fractional area change was significantly decreased post-exercise (40.5±6.2%) compared to a significant increase during pharmacological stress echocardiography (72.6±7.3%). Serum cardiac troponin I concentration was significantly higher 2h after the pharmacological test compared to baseline values and post-exercise, although the highest value was found post-exercise in the horse with the highest systolic pulmonary artery pressure and lowest right ventricular fractional area change. Pharmacological stress testing is not recommended in further studies on right ventricular adaptations in athletic horses, as this does not reproduce the effects of exercise.

Reasons for performing the study Atrial fibrillation (AF) is the most important dysrhythmia affecting performance in horses and has been associated with incoordination, collapse and sudden death. Limited information is available on ventricular response during exercise in horses with lone AF. Objectives To investigate ventricular response in horses with lone AF during a standardised lungeing exercise test. Methods A modified base-apex electrocardiogram was recorded at rest and during a standardised lungeing exercise test from 43 horses diagnosed with lone AF. During the test horses walked for 7min, trotted for 10min, cantered for 4min, galloped for 1min and recovered for 7min. Results Individual average heart rate during walk ranged from 42 to 175beats/min, during trot from 89 to 207 beats/min, during canter from 141 to 269 beats/min, and during gallop from 191 to 311 beats/min. Individual beat-to-beat maximal heart rate ranged from 248 to 492 beats/min. Ventricular premature depolarisations were present in 81% of the horses: at rest (16%), during exercise (69%), and during recovery (2%). In 33% of the horses, broad QRS complexes with R-on-T morphology were found. Conclusions Exercising horses with lone AF frequently develop disproportionate tachycardia. In addition, QRS broadening and even R-on-T morphology is frequently found. QRS broadening may originate from ventricular ectopic foci or from aberrant intraventricular conduction, for example due to bundle branch block. This might explain the high number of complexes currently classified as ventricular premature depolarisations. Potential relevance Prevalence of QRS broadening and especially R-on-T was very high in horses with AF and was found at low levels of exercise. These dysrhythmias are considered risk factors for the development of ventricular tachycardia and fibrillation and they might explain signs of weakness, collapse or sudden death that have been reported in horses with AF.

Reasons for performing study: The use of two-dimensional speckle tracking (2DST) for quantification of left ventricular (LV) function has recently been described in horses using long-axis images and short-axis images at chordal but not at papillary muscle level. Objectives: To compare the feasibility and reliability of 2DST for quantification of circumferential and radial LV function in short-axis images at papillary muscle and chordal level. Methods: Repeated echocardiographic examinations were performed on ten healthy trotter horses by two observers from a right parasternal short-axis view at papillary muscle and chordal level. Segmental and averaged peak values and timing of circumferential and radial strain and strain rate, radial displacement and rotation were measured in six LV wall segments in each imaging plane. Global peak values were calculated for circumferential strain and strain rate. The inter- and intra-observer within- and between-day variability was assessed by calculating coefficients of variation for repeated measurements. Results: 2DST analysis was feasible in each cardiac cycle although tracking was often inadequate during early diastole. Measurements of averaged systolic circumferential and radial strain and strain rate and radial displacement as well as global circumferential strain and strain rate could be determined with low variability. Early and late diastolic strain rate and systolic rotation showed a moderate variability. Radial segmental measurements were more reliable than circumferential measurements. The interventricular septum showed a higher circumferential and lower radial strain compared to the LV free wall. Peak timing was earlier at papillary muscle compared to chordal level. Conclusions: 2DST measurements of global and regional circumferential and radial LV wall motion are feasible both at papillary muscle and chordal level. Potential relevance: Several measurements showed good reliability and can be used when evaluating the technique in a clinical setting.

Reasons for performing study: In human medicine, esophageal electrocardiography (ECG) is a well-established technique that magnifies P waves with respect to the QRS complex. Objectives: To investigate the feasibility of esophageal ECG recording and its ability to produce larger P waves compared to base-apex and unipolar recordings. Methods: Bipolar and unipolar ECG were performed using esophageal and surface electrodes. Esophageal ECG was obtained from six different recording configurations at different esophageal depths. Amplitudes of P, Q, R, S and T waves were measured from three different cardiac cycles for each recording configuration and depth. Results: Esophageal ECG was feasible in all horses. For all esophageal recording configurations, significantly larger P waves were recorded from a depth that equaled ‘height of the withers +10 cm’ (HW+10) than from any other depth. P/QRSmagn, the ratio between the P wave and QRS complex magnitudes, was largest for intra-esophageal recordings with an interelectrode distance of 10 cm, at HW+10, where it was significantly larger than base-apex and unipolar recordings. Base-apex recording resulted in significantly smaller P waves than all other recording configurations and significantly smaller P/QRSmagn ratios than all other recording configurations except one combined esophageal-surface recording (E/Slow). Conclusions: Esophageal ECG recording is feasible in horses and effective in magnifying P wave amplitude. Potential relevance: The procedure is promising for diagnosis of supraventricular tachydysrhythmias and might be used in electrophysiological studies and for cardiac pacing.

A turbidimetric method to determine serum C-reactive protein (CRP) concentration, based on soybean oil–phosphocholine interaction, was performed on horse serum samples to evaluate its potential diagnostic value in veterinary medicine. Intralipid 20% in 0.1 M Tris–calcium buffer (pH 7.5) was added to horse serum. After 30 min of incubation at 37°C, the CRP–phosphocholine complexes were turbidimetrically, bichromatically (660 nm/700 nm) quantified on a commercial analyzer. Furthermore, comparison between CRP and other inflammatory markers, including white blood cell and neutrophil counts, was performed to evaluate the diagnostic value of both tests. Standardization of the assay was done using a commercial human CRP calibrator. The CRP measurements were performed on serum samples (296 patients and 34 controls). Reference values were found to be lower than 10 mg/l. The method was found to be linear between 1 and 400 mg/l. A moderate correlation was observed between CRP values and the relative neutrophil counts. Receiver-operating characteristics analysis demonstrated the area under the curve for CRP was 0.928, which was superior ( P < 0.001) to the neutrophil count (0.804) and the leukocyte count (0.664) in detecting the presence of inflammation. This CRP assay showed reliable results as an acute phase test in horses, confirming its species-independent capability to detect CRP in various mammals, including horses.

Background: The quantification of equine left ventricular (LV) function is generally limited to short-axis M-mode measurements. However, LV deformation is 3-dimensional (3D) and consists of longitudinal shortening, circumferential shortening, and radial thickening. In human medicine, longitudinal motion is the best marker of subtle myocardial dysfunction. Objectives: To evaluate the feasibility and reliability of 2-dimensional speckle tracking (2DST) for quantifying equine LV longitudinal function. Animals: Ten healthy untrained trotter horses; 9.6 ± 4.4 years; 509 ± 58 kg. Methods: Prospective study. Repeated echocardiographic examinations were performed by 2 observers from a modified 4-chamber view. Global, segmental, and averaged peak values and timing of longitudinal strain (SL), strain rate (SrL), velocity (VL), and displacement (DL) were measured in 4 LV wall segments. The inter- and intraobserver within- and between-day variability was assessed by calculating the coefficients of variation for repeated measurements. Results: 2DST analysis was feasible in each exam. The variability of peak systolic values and peak timing was low to moderate, whereas peak diastolic values showed a higher variability. Significant segmental differences were demonstrated. DL and VL presented a prominent base-to-midwall gradient. SL and SrL values were similar in all segments except the basal septal segment, which showed a significantly lower peak SL occurring about 60 ms later compared with the other segments. Conclusions and Clinical Importance: 2DST is a reliable technique for measuring systolic LV longitudinal motion in healthy horses. This study provides preliminary reference values, which can be used when evaluating the technique in a clinical setting.

Little information is available on medical imaging of the adrenal glands in horses. We investigated the feasibility of transrectal ultrasonography to characterize the normal equine adrenal gland. Transrectal ultrasonography was performed in 25 healthy horses using a 7.5 MHz linear array probe at a displayed depth of 8 cm. Transrectal ultrasonography of the right adrenal gland was not feasible. For the left adrenal gland, the left kidney, the abdominal aorta, the left renal artery, the left renal vein, and the cranial mesenteric artery were used as landmarks. The size of the left adrenal gland was variable, but it generally appeared as a long, flat structure with a hyperechoic medulla surrounded by a hypoechoic cortex. The most cranial part of the gland could not be delineated appropriately in 11 horses (44%). The mean (+/-SD) thickness of the gland and medulla was 0.66 +/- 0.15cm (n = 25) and 0.28 +/- 0.09 cm (n = 25) near the caudal pole, 0.87 +/- 0.25 cm (n = 14) and 0.40 +/- 0.18 cm (n = 12) near the cranial pole, and 0.89 +/- 0.18 cm (n = 25) and 0.36 +/- 0.13 cm (n = 25) in the middle of the gland, respectively. The mean (+/-SD) length of the entire adrenal gland and of the medulla was 6.22 +/- 0.77 cm (n = 14) and 5.45 +/- 0.71 cm (n = 6), respectively. Transrectal ultrasonography allowed adequate visualization of the left adrenal gland in horses.

Objective—To investigate effects of IV administration of propafenone for naturally occurring and experimentally induced chronic atrial fibrillation in horses. Animals—2 horses with naturally occurring atrial fibrillation and 4 horses with pacing-induced atrial fibrillation. Procedures—Horses received a bolus of propafenone (2 mg/kg, IV over 15 minutes). If atrial fibrillation persisted after 20 minutes, a continuous infusion of propafenone (7 μg/kg/min) was given for 120 minutes. Before, during, and after treatment, plasma propafenone concentrations, hematologic and serum biochemical values, and electolyte concentrations analyses were determined and clinical signs were monitored. Surface ECGs were recorded. If propafenone treatment failed, quinidine sulfate was administered. Results—Bolus and continuous infusion induced minimal adverse effects. During the 15-minute bolus administration, a slight increase in heart rate was observed and horses appeared more sensitive to external stimuli. Throughout treatment, no significant changes were observed in respiratory rate, QRS or corrected QT duration, or results of hematologic analyses. Although a significant increase in F-wave interval and atrial fibrillation cycle length was observed and plasma propafenone concentrations (569 to 1,268 ng/mL) reached the human therapeutic range (64 to 1,044 ng/mL), none of the horses cardioverted to sinus rhythm. Sinus rhythm could be restored in all horses via standard oral administration of quinidine. Conclusions and Clinical Relevance—A slow IV bolus of 2 mg of propafenone/kg followed by a continuous infusion of 7 μg/kg/min over 2 hours was not an effective treatment for chronic atrial fibrillation in horses.