Assessment of left ventricular function in horses with aortic regurgitation by 2D speckle tracking

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.

Aortic, common carotid and external iliac artery arterial wall stiffness parameters in horses: Inter-day and inter-observer and intra-observer measurement variability

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.

Atrial and ventricular electrical and contractile remodelling and reverse remodelling due to chronic pacing-induced atrial fibrillation in horses: preliminary results

In humans, electrical and contractile reverse remodelling following restoration of sinus rhythm (SR) after a prolonged period of spontaneous atrial fibrillation (AF), requires several weeks. There is little known about this phenomenon in horses. In the present study, six healthy horses were instrumented with a neurostimulator and a pacemaker to maintain AF for four months by intermittent burst pacing and to study atrial and ventricular electrophysiology. AF became persistent in all horses after two to six weeks of burst pacing. Before, during and after the AF period, parameters, such as the atrial fibrillation cycle length, the right atrial and ventricular refractory period and vulnerability, such as inducing atrial arrythmias, atrial tachyarrythmias or maintaining AF, were determined. Two-dimensional echocardiography was used to measure atrial and ventricular contractility expressed as fractional shortening and size expressed as diameter and area. In two of the six horses, the procedure was discontinued due to an increased threshold (1 horse) and due to infection at the level of the pacemaker pocket (1 horse). In the four remaining horses, significant electrical and contractile remodelling compared to baseline values was observed from 48 hours onwards after AF induction. Upon restoration of SR with quindine sulfate, all electrical and contractile values returned to normal within one to two months. No ventricular remodelling was observed. Four months of pacing-induced AF resulted in electrical and contractile remodelling and reverse remodelling. The results suggest that pacing-induced chronic AF does not cause permanent damage and suggest that a resting period of six to eight weeks before returning to training might be beneficial.

Atrial premature depolarisations five days post electrical cardioversion are related to atrial fibrillation recurrence risk in horses

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<0.001), left atrial active fractional area change ≤9.6% (HR 2.6, 95% CI 1.0-6.5, P = 0.04) and lower body weight (HR 0.99, 95% CI 0.98-0.99, P = 0.001) were significantly associated with AF recurrence.

MAIN LIMITATIONS

This study did not evaluate early AF recurrence within 5 days. The results cannot necessarily be extrapolated to other treatment methods, as only horses converted by TVEC were included.

CONCLUSIONS

The APD burden 5 days post cardioversion could be a useful predictive value for AF recurrence within 1 year in horses. However, other factors such as mitral regurgitation and atrial contractile function must also be taken into account.

Percutaneous transcatheter closure of an aorto-cardiac fistula in a six-year-old Warmblood mare with atrial fibrillation

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.

Assessing the potential of the qualitative trajectory calculus to detect gait pathologies: a case study of children with developmental coordination disorder

The Qualitative Trajectory Calculus (QTC) is a qualitative spatio-temporal calculus for describing interactions between moving point objects. So far, it remained unclear whether QTC is useful for describing subtle differences, such as between the movements of different parts of a human body. We tested the applicability of QTC to detect differences in the gait patterns of children with or without Developmental Coordination Disorder (DCD). We found that using a combination of three markers (i.e. ankle, toe and trochanter), QTC can achieve a high classification accuracy (i.e. 83.3%) of classifying subjects correctly to either the DCD group or the control group.

The risk of flax versus straw bedding on ileal impaction in colic horses: Retrospective analysis of 2336 cases (2008-2017)

While mature coastal bermudagrass hay is strongly associated with ileal impaction in the Southeastern United States, stabling on flax bedding has anecdotally been associated with this condition in Europe. The aim of this retrospective study was to investigate the association between ileal impaction and the use of flax shives compared to straw as bedding in horses with colic. Medical records of 2336 referral cases evaluated for abdominal pain between January 2008 and May 2017 at the Department of Large Animal Internal Medicine, Ghent University were reviewed. Diagnosis, date of admission, age, breed, gender, body weight and stable bedding were recorded. Conditional logistic regression analysis was used to assess the association between ileal impaction and each individual variable. Odds ratios (OR) and 95% confidence intervals (CI) were determined. Predictors with a value of P < 0.2 were included in a multivariable Cox regression model and Wald’s test was used to assess parameter estimate significance. Further, the association between survival to discharge and type of bedding or type of treatment (medical versus surgical) was analyzed for horses with ileal impactions. The proportion of colic cases stabled on flax bedding at home was 11.3%. The overall prevalence of ileal impaction was 4.2%. In the flax group, the prevalence of ileal impaction was 9.4% as opposed to 3.6% within the straw group. The OR of 2.8 (95% CI 1.7-4.7; P < 0.001) in the multivariable logistic regression model indicated that horses stabled on flax shives were approximately three times more likely to have ileal impactions than horses stabled on straw. There was no significant association found between ileal impaction and the period of admission, age, gender or body weight in a multivariable logistic regression model. The odds for having ileal impaction is approximately six times (OR 6.3; 95% CI 2.4-16.4; P < 0.001) higher in draft horses than in warmbloods in the multivariable logistic regression model. No significant association was found between survival to discharge and type of bedding or treatment. These results suggest that horses with colic that were housed on flax bedding are more likely to present ileal impactions than horses housed on straw.

Can heart rate variability parameters derived by a heart rate monitor differentiate between atrial fibrillation and sinus rhythm?

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.

Detection of subclinical left ventricular dysfunction by tissue Doppler imaging in horses with aortic regurgitation

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.

Pharmacokinetics and electrophysiological effects of sotalol hydrochloride in horses

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 β-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.

Pheochromocytoma in a horse with polymorphic ventricular tachycardia

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.

Exoskeleton plantarflexion assistance for elderly

Elderly are confronted with reduced physical capabilities and increased metabolic energy cost of walking. Exoskeletons that assist walking have the potential to restore walking capacity by reducing the metabolic cost of walking. However, it is unclear if current exoskeletons can reduce energy cost in elderly. Our goal was to study the effect of an exoskeleton that assists plantarflexion during push-off on the metabolic energy cost of walking in physically active and healthy elderly. Seven elderly (age 69.3±3.5y) walked on treadmill (1.11ms²) with normal shoes and with the exoskeleton both powered (with assistance) and powered-off (without assistance). After 20min of habituation on a prior day and 5min on the test day, subjects were able to walk with the exoskeleton and assistance of the exoskeleton resulted in a reduction in metabolic cost of 12% versus walking with the exoskeleton powered-off. Walking with the exoskeleton was perceived less fatiguing for the muscles compared to normal walking. Assistance resulted in a statistically nonsignificant reduction in metabolic cost of 4% versus walking with normal shoes, likely due to the penalty of wearing the exoskeleton powered-off. Also, exoskeleton mechanical power was relatively low compared to previously identified optimal assistance magnitude in young adults. Future exoskeleton research should focus on further optimizing exoskeleton assistance for specific populations and on considerate integration of exoskeletons in rehabilitation or in daily life. As such, exoskeletons should allow people to walk longer or faster than without assistance and could result in an increase in physical activity and resulting health benefits.

What does normal tendon structure look like? New insights into tissue characterization in the Achilles tendon

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 < 0.001). Furthermore, female tendons contained significantly more echo type II, in both insertion and midportion compared with male tendons (P = 0.004 and P = 0.003, respectively). The results of this study, with respect to the MDC (minimum detectable change), highlight differences in the UTC echopattern in the normal population (sex and regional location), which are important considerations for future studies.

Atrial Premature Depolarization-Induced Changes in QRS and T Wave Morphology on Resting Electrocardiograms in Horses

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.

Total plasma proANP increases with atrial dilatation in horses

Equine atrial natriuretic peptide (ANP) plasma concentrations are correlated with left atrial size. However, species-specific assays are lacking and the results from human assays are poorly reproducible. A new methodology called processing independent analysis (PIA) that measures the total proANP product in plasma has proven to be successful in human medicine, but has never been used in horses. The aims were to establish an equine proANP reference interval by measurement of the total proANP product using PIA and to examine the proANP concentrations in horses with atrial dilatation. Sample stability was studied by comparison of storage at -80°C and -20°C. Plasma samples were obtained from 23 healthy horses, 12 horses with moderate or severe valvular regurgitation without atrial dilatation and 42 horses with valvular regurgitation and atrial dilatation. The proANP concentration was significantly (P<0.001) higher in horses with atrial dilatation (761.4 (442.1-1859.1) pmol/l) than in healthy horses (491.6 (429.5-765.9) pmol/l; P<0.001) or horses with cardiac disease but without atrial dilatation (544.4 (457.0-677.6) pmol/l). A cut-off value (573.8 pmol/l) for detection of atrial dilatation was calculated. Sample storage at -80°C did not differ from sample storage at -20°C. The measurement of total proANP in plasma detects atrial dilatation in horses and may be useful for clinical evaluation in equine medicine.

Cardiac troponin I as compared to troponin T for the detection of myocardial damage 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.

Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015

REASONS FOR PERFORMING THE STUDY

Yellow fat disease or steatitis is characterised by a local or general inflammation of fat tissue and is occasionally found in horses. Diagnosis is challenging because of the wide range of nonspecific clinical signs.

OBJECTIVES

To describe clinical signs, treatment, outcome and ultrasonographic findings in horses with steatitis.

STUDY DESIGN

Retrospective study (January 2008 to January 2015).

METHODS

History, clinical signs, ultrasonographic findings, diagnosis, treatment and outcome were recorded.

RESULTS

Twenty cases (18 horses, 2 donkeys; 9 mares, 9 stallions, 2 geldings) were retrieved from 13,707 patient records. Mean age was 1.6 (± 0.8) years (range 1 month-3.5 years). All cases appeared between October and February except for one (August). History included dullness, recumbency, decreased appetite and weight loss. Fever, ventral oedema, stiff/painful gait and 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. Subperitoneal, perirenal, mesenteric, coronary and caudal mediastinal fat showed homogenously increased echogenicity. Especially the subperitoneal fat 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 retroperitoneal fat in the ventral flank. In all horses where fat biopsy was taken (n = 13), steatitis was confirmed. Treatment consisted of selenium and vitamin E (intra-muscular injection followed by oral treatment) supplementation and anti-inflammatory treatment (dexamethasone or prednisolone parenteral or oral) for at least 1-4 weeks. Fourteen animals (70%) survived. Full recovery took about 2-6 months.

CONCLUSIONS

Yellow fat disease may be underdiagnosed because of the nonspecific clinical signs. Ultrasound was extremely helpful for making a diagnosis. Recovery was rather slow but was achieved in 70% of the animals. Ethical animal research: Research ethics committee oversight not currently required by this conference: retrospective study of clinical records. Explicit owner informed consent for inclusion of animals in this study was not stated.

SOURCE OF FUNDING

Ghent University (institutional). Competing interests: None declared.

Hemothorax bij een Fries paard: niet altijd een aortaruptuur!

Een zestienjarige Friese ruin werd aangeboden op de vakgroep Interne Geneeskunde van de Grote Huisdieren, Faculteit Diergeneeskunde (UGent), met klachten van inspanningsintolerantie, bleke mucosae, tachycardie en een onregelmatig hartritme. Uit het algemeen onderzoek bleek een demping van hart- en ventrale longgeluiden. Dit, in combinatie met een lage hematocriet, deed het vermoeden van hemothorax rijzen. De diagnose van hemothorax kon bevestigd worden aan de hand van thoracale echografie en thoracocentesis. Daar het een Fries paard betrof werd onmiddellijk gedacht aan een aortopulmonale fistel, maar dit kon echter uitgesloten worden aan de hand van uitgebreid echocardiografisch onderzoek. Uit het elektrocardiogram kon afgeleid worden dat het onregelmatig hartritme te wijten was aan atriale extrasystolen. Het paard werd gehospitaliseerd en conservatief behandeld met breedspectrumantibiotica. Daar zowel de hematocriet als het echografische beeld gunstig evolueerde, mocht het paard na vijftien dagen de kliniek verlaten. Bij controle zes weken later werden geen afwijkingen meer gevonden.

Equine BNP measurement using a porcine BNP enzyme-linked immunoassay: a pilot study

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°C and -80°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°C showed significantly (72.19, 24.69-513.36 pg/mL; P=0.001) higher concentrations than samples stored at -20°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.

Risk factors for recurrence of atrial fibrillation in horses after cardioversion to sinus rhythm

Background

Although atrial fibrillation (AF) can be successfully treated in horses, recurrence occurs frequently. In humans, atrial function after cardioversion can predict recurrence.

Objectives

To examine the prognostic value of atrial mechanical function at 24 hours after cardioversion and other potential predictor variables for AF recurrence in horses.

Animals

117 horses treated for AF at 4 referral centers.

Methods

Retrospective study. Inclusion criteria were successful cardioversion, echocardiography at 24 hours after cardioversion and ≥4 months follow‐up. To determine factors associated with AF recurrence, a multivariable survival model was built.

Results

133 AF episodes in 117 horses were included. AF recurred in 36/100 horses with a first AF episode and in 57/133 AF episodes overall. Factors associated with recurrence in horses with a first episode were previous unsuccessful treatment attempt (hazard ratio HR 2.36, 95% confidence interval CI 1.11–4.99, P = .025) and mild or moderate mitral regurgitation (HR 2.70, 95% CI 1.23–5.91, P = .013). When the last AF episode of all horses was included, previous AF (HR 2.53, 1.33–4.82, P = .005) and active left atrial fractional area change ≤9.6% (HR 3.43, 1.22–9.67, P = .020) were significant predictors.

Conclusions and Clinical Importance

The only echocardiographic variable of left atrial function with significant prognostic value for recurrence was low active left atrial fractional area change. Further research is necessary to evaluate whether echocardiography at a later timepoint could provide more prognostic information.

A multifactorial injury prevention intervention reduces injury incidence in Physical Education Teacher Education students

Physical Education Teacher Education (PETE) students are at considerable risk for non-contact sports injuries of the lower extremities. Multifactorial injury prevention interventions including exercises have been successful in sports populations, but no such study has ever been performed in PETE students. This study investigated the efficacy of a multifactorial injury prevention intervention on injury incidence reduction in PETE students. PETE students in the intervention group (n = 154) and in the control group (n = 189) registered sports injuries prospectively. The intervention lasted one academic year and consisted of an injury awareness programme and preventive strategies, implemented by the PETE sports lecturers. Differences in injury incidence between the intervention and control group were tested by Poisson regression Wald tests. There was a trend towards significantly lower incidence rate (2.18 vs. 2.73; p = 0.061) in the intervention group compared with the control group. Students in the intervention group had significantly less acute, first-time and extracurricular injuries. The largest reduction was observed for injuries during unsupervised practice sessions. A multifactorial injury prevention intervention embedded into a regular PETE programme is a promising and feasible strategy to prevent injuries in PETE students. Further research is needed to investigate whether the results may be generalised to other PETE programmes.

Uphill walking with a simple exoskeleton: plantarflexion assistance leads to proximal adaptations

While level walking with a pneumatic ankle-foot exoskeleton is studied extensively, less is known on uphill walking. The goals of this study were to get a better understanding of the biomechanical adaptations and the influence of actuation timing on metabolic cost during uphill walking with a plantarflexion assisting exoskeleton. Seven female subjects walked on a treadmill with 15% inclination at 1.36 ms(-1) in five conditions (4 min): one condition with an unpowered exoskeleton and four with a powered exoskeleton with onset of pneumatic muscle actuation at 19, 26, 34 and 41% of stride. During uphill walking the metabolic cost was more than 10% lower for all powered conditions compared to the unpowered condition. When actuation onset was in between 26 and 34% of the stride, metabolic cost was suggested to be minimal. While it was expected that exoskeleton assistance would reduce muscular activity of the plantarflexors during push-off, subjects used the additional power to raise the body centre of mass in the beginning of each step to a higher point compared to unpowered walking. This reduced the muscular activity in the m. vastus lateralis and the m. biceps femoris as less effort was necessary to reach the highest body centre of mass position in the single support phase. In conclusion, subjects can use plantarflexion assistance during the push-off to reduce muscular activity in more proximal joints in order to minimize energy cost during uphill locomotion. Kinetic data seem necessary to fully understand this mechanism, which highlights the complexity of human-exoskeleton interaction.

Kinematics and dynamics of burst transitions

Subjects (N = 14) were instructed to walk at comfortable walking speed and to start sprinting on an external (visual) stimulus. This is a burst transition. To accelerate maximally, different strategies can be used. The choice for a strategy was hypothesized to be (a) dependent of the body's dynamical status, which is in its turn dependent on the signal timing within the gait cycle; and (b) influenced by the performance and efficacy of the different strategies. Three-dimensional kinematics and ground reaction forces were used to discriminate between strategies and to calculate work (W(total)). Distance laser data yielded performance measures and the work related to the forward acceleration (W(objective)). Efficacy was calculated as the ratio of W(objective) to W(total). Subjects mainly used 2 strategies among others depending on the timing of the stimulus: (a) subjects placed their body center of mass (BCOM) in front of their center of pressure (COP) by tilting the trunk forward and flexing the knee, resulting in a sudden forward acceleration but a relatively fair efficacy; (b) subjects placed their COP behind their BCOM by placing the foot of the swing leg backward. This led to a high performance with high efficacy and was therefore the most ecologically relevant.

Gelokaliseerde steatitis als complicatie na dystokie bij een merrie

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.

Atrial fibrillation cycle length and atrial size in horses with and without recurrence of atrial fibrillation after electrical cardioversion

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 1 year 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 ± 24 milliseconds, respectively, and in those maintaining SR (n = 12 or 67%) 166 ± 13 and 141 ± 13 milliseconds, 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.

Adaptation to walking with an exoskeleton that assists ankle extension

The goal of this study was to investigate adaptation to walking with bilateral ankle-foot exoskeletons with kinematic control that assisted ankle extension during push-off. We hypothesized that subjects would show a neuromotor and metabolic adaptation during a 24min walking trial with a powered exoskeleton. Nine female subjects walked on a treadmill at 1.36±0.04ms(-1) during 24min with a powered exoskeleton and 4min with an unpowered exoskeleton. Subjects showed a metabolic adaptation after 18.5±5.0min, followed by an adapted period. Metabolic cost, electromyography and kinematics were compared between the unpowered condition, the beginning of the adaptation and the adapted period. In the beginning of the adaptation (4min), a reduction in metabolic cost of 9% was found compared to the unpowered condition. This reduction was accompanied by reduced muscular activity in the plantarflexor muscles, as the powered exoskeleton delivered part of the necessary ankle extension moment. During the adaptation this metabolic reduction further increased to 16%, notwithstanding a constant exoskeleton assistance. This increased reduction is the result of a neuromotor adaptation in which subjects adapt to walking with the exoskeleton, thereby reducing muscular activity in all leg muscles. Because of the fast adaptation and the significant reductions in metabolic cost we want to highlight the potential of an ankle-foot exoskeleton with kinematic control that assists ankle extension during push-off.

The use of cardiac biomarkers in veterinary medicine: the equine perspective

In human medicine, cardiac biomarkers, such as natriuretic peptides and troponins, are routinely used for the diagnosis, prognosis and monitoring of heart diseases. Similarly, these biomarkers are determined in small animals to differentiate non-cardiac from cardiac diseases. Knowledge about these biomarkers in horses is limited and requires further investigation. The first equine studies about atrial natriuretic peptide (ANP) and N-terminal ANP (NT-proANP) are promising, and show a clear correlation with atrial dimension size. Equine brain natriuretic peptides assays are still unavailable. The troponins, in particular troponin I, have been more extensively studied in horses, and their use for the diagnosis of myocardial damage has been fully demonstrated. They have replaced the less specific lactate dehydrogenase and creatine kinase isoenzymes, which makes the use of the last mentioned no longer legitimate. A final possible equine biomarker is aldosterone. Reference values in horses have been established. However, in only one study, a correlation between aldosterone and cardiac disease has been reported.

Ventricular response during lungeing exercise in horses with lone atrial fibrillation

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 7 min, trotted for 10 min, cantered for 4 min, galloped for 1 min and recovered for 7 min.

RESULTS

Individual average heart rate during walk ranged from 42 to 175 beats/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.

Quadriceps muscle fatigue in trained and untrained boys

This study aimed to explore muscle oxygen extraction and muscle activation pattern during bilateral intermittent submaximal isometric knee-extensions by combining Near-infrared Spectroscopy (NIRS) and Electromyography (EMG) measurements from the M. Vastus Lateralis. A group of highly specifically trained boys (youth sailors) (n=10) and untrained matched controls (n=10) performed 12 bouts of 90 s bilateral submaximal (30-40% MVC) isometric knee-extension interspersed with 6 s recovery-periods. Patterns of deoxygenated haemoglobin and myoglobin concentration (Deoxy[Hb+Mb]) were observed during each bout and the entire protocol. Reoxygenation Index (RI) was assessed for each recovery period as the amplitude of Deoxy[Hb+Mb]-decrease relative to amplitude of Deoxy[Hb+Mb]-increase during each bout. Root Mean Square (RMS) and Mean Power Frequency (MPF) were calculated for each bout as an average of the final 60 s. Deoxy[Hb+Mb], RI, RMS and MPF were analyzed by repeated-measures ANOVA. Results indicated significantly higher Deoxy[Hb+Mb]-increase and lower RI in specifically trained boys compared to untrained controls. These differences are presumably related to the differences in EMG-measurements which demonstrated lower RMS-increase and MPF-decrease for trained compared to untrained boys. In conclusion, specifically trained boys indicate delayed onset of muscle fatigue in comparison to untrained controls, which might be associated with the different pattern of muscle O2-extraction or muscle activation pattern (i. e., a more accurate recruitment of slow-twitch fibres).

Cardiac changes in horses with atypical myopathy

BACKGROUND

Atypical myopathy (AM) is an acute, fatal rhabdomyolysis in grazing horses that mainly affects skeletal muscles. Postmortem examinations have shown that myocardial damage also occurs. Limited information is available on the effect of AM on cardiac function in affected and surviving horses.

OBJECTIVES

To describe electrocardiographic and echocardiographic changes associated with AM in the acute stage of the disease and after follow-up.

ANIMALS

Horses (n = 12) diagnosed with AM in which cardiac ultrasound examination and ECG recording were available.

METHODS

All horses underwent clinical examinations, serum biochemistry, electrocardiography, and echocardiography. Four surviving horses underwent the same examinations after 2-10 weeks.

RESULTS

All but 1 horse had increased cardiac troponin I concentrations and 10 horses had ventricular premature depolarizations (VPDs). All horses had prolonged corrected QT (QT(cf) ) intervals on the day of admission and abnormal myocardial wall motion on echocardiography. One of the surviving horses still had VPDs and prolonged QT(cf) at follow-up after 10 weeks.

CONCLUSIONS AND CLINICAL IMPORTANCE

The AM results in characteristic electrocardiographic and echocardiographic changes and may be associated with increased cardiac troponin I concentrations and VPDs. In survivors, abnormal cardiac function still may be found at follow-up after 10 weeks. Additional research in a larger group of horses is necessary to identify the long-term effects of AM on cardiac function.